Even though it is normal to place the wire between two layers of glass, it often moves from its original placing.
Using glue only keeps the wire in place while moving the piece(s) to the kiln. The glue will burn off at just under 500C, which is before the sticky point of glass, so it cannot hold the wire in place at the critical temperature – from about 700C. In fact, if you fire quickly the glue can “boil” and cause the wire to move.
There are a variety of methods to help keep the wire where you placed it. Some of them follow.
You can try weighting the wire down with small scraps of glass to keep the wire in place until the glass sticks to the wire. The scrap will often form a small bead that can be used in other projects. Sometimes though, the scrap sticks to the wire.
Another method is to place a small piece of 3mm fibre paper under the wire to support it during the firing. This will be enough to keep the wire from moving, and the scraps of fibre paper can be reused many times.
You could also bend the wire loop so that the end touches the shelf. The part in between the glass needs to be flat with the bend starting after the wire emerges from the glass. You can bend the wire straight after firing.
Flattening the wire by tapping the wire – placed on an anvil – with a hammer will reduce the possibilities of movement, and certainly any rolling possibilities. It will also have a greater area of contact with the glass.
You can also make a shallow groove in the glass where the wire is to go. This can be done with a Dremel type tool with a diamond bit, or on the small diameter bit on the top of a glass grinder.
Lay the glass in the groove and cap with the top piece.
Wednesday, 12 May 2010
Drilling Glass 1
Keeping Things Wet
It is important always to keep the drill bit and glass wet, otherwise the glass gets too hot and will break. There are a variety of things you can do to achieve this.
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits in glass
It is important always to keep the drill bit and glass wet, otherwise the glass gets too hot and will break. There are a variety of things you can do to achieve this.
- Drill under water in a container
- Drill in a ring of clay, plasticine, etc., holding water. To do this, you need to make a ring about 50mm / two inches in diameter and press it around the drill site. Fill the ring with water and a little diamond coolant. This will cool the drill site and glass. Diamond coolant is not necessary, but extends the life of the bits.
- Use a recirculating water pump such as those made for indoor water features. Direct the small flow of water to the drilling site and catch the water in the bucket in which the pump is submerged.
- Use a glass drill with hollow core bits and an internal water feed. This is the most expensive but it is the best equipment with which to drill large holes.
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits in glass
Drilling Glass, 3
Drilling with a Flushing Head
A flushing head with a re-circulating pump will deliver water to the drill site through the core of the drill. These are supplied complete or as a fitting for an existing drill press. This is suitable for holes of 4mm and larger. Smaller core drills are impractical both because the glass is easily trapped in the drill and the wall thickness of the drill makes them almost solid anyway.
An additional requirement is to have a means to direct the water back to the reservoir.
Every diameter drill bit has an optimum drill speed. The smaller they are the faster the speed. Drill presses do tend to be on the slow side for glass drilling, but often have ways of altering the speed. So it takes a bit longer, but there are big advantages in other respects.
Don't push down any harder than you comfortably can with the tips of your fingers. Keep it steady. Listen for the sound of diamond grinding glass
If the core gets stuck in the bit, knock it out with some stiff wire or a nail. Be careful not to damage the edges of the drill bit. Always remove each core right after drilling. They are difficult to remove if there is more than one in the core of the bit.
For other tips on glass drilling see:
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits in glass
A flushing head with a re-circulating pump will deliver water to the drill site through the core of the drill. These are supplied complete or as a fitting for an existing drill press. This is suitable for holes of 4mm and larger. Smaller core drills are impractical both because the glass is easily trapped in the drill and the wall thickness of the drill makes them almost solid anyway.
An additional requirement is to have a means to direct the water back to the reservoir.
Every diameter drill bit has an optimum drill speed. The smaller they are the faster the speed. Drill presses do tend to be on the slow side for glass drilling, but often have ways of altering the speed. So it takes a bit longer, but there are big advantages in other respects.
Don't push down any harder than you comfortably can with the tips of your fingers. Keep it steady. Listen for the sound of diamond grinding glass
If the core gets stuck in the bit, knock it out with some stiff wire or a nail. Be careful not to damage the edges of the drill bit. Always remove each core right after drilling. They are difficult to remove if there is more than one in the core of the bit.
For other tips on glass drilling see:
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits in glass
Drilling Glass, 4
Avoiding Chipping
There are a number of methods to avoid chipping out the back of the glass when drilling:
All these things will help to avoid chipping out the glass at the bottom of the hole.
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits
There are a number of methods to avoid chipping out the back of the glass when drilling:
- Placing a piece of scrap glass under your good glass will help avoid chipping on the backside. By pressing firmly but gently on the glass (not the bit) the bit will go through the upper piece of glass without chipping the back. This can be a difficult process to keep stable when both the pieces of glass are wet.
- Another method is to put duct tape under the glass to help minimise chip out.
Drill from both sides to avoid chip out as the bit breaks through. Go slowly toward the bottom of the hole. When the hole is almost through, turn the glass over and drill back to front. - Sometimes the glass is curved and drilling from the back is not easy. This is when the drill press mechanism to stop the bit sliding comes into its own. Before switching the drill on, lower it to the surface supporting the glass. You can adjust the mechanism to stop the press just as it reaches the support surface. Then place the glass under the press and the turn the drill on to begin the drilling.
- Don't push hard as you come to the end. Don't push down any harder on the drill press levers than you comfortably can with the tips of your fingers throughout the process. Keep it steady. Listen for the sound of diamond grinding glass.
All these things will help to avoid chipping out the glass at the bottom of the hole.
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits
Drilling Glass, 5
Drilling holes with copper tube and grit
You can drill holes by using loose grit and a copper tube of the correct diameter. It can take quite a while. You will need to have a chuck big enough to take the tube, or have a means to reduce the tube diameter to the chuck size. Alternatively, use core drills that have had the diamonds worn away.
Prepare the glass as for a drill press without a flushing head, so the water and grit are confined. The dam can be putty, plasticine, clay, or other mouldable material put around the area to be drilled.
The grit can be sandblast grit or other abrasive of about 100 to 200 grit.
Drill as normal.
If the core gets stuck in the bit, knock it out with some stiff wire or a nail. Always remove each core right after drilling. They are very difficult to remove if there is more than one in the core of the bit.
For other tips on glass drilling see:
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits in glass
You can drill holes by using loose grit and a copper tube of the correct diameter. It can take quite a while. You will need to have a chuck big enough to take the tube, or have a means to reduce the tube diameter to the chuck size. Alternatively, use core drills that have had the diamonds worn away.
Prepare the glass as for a drill press without a flushing head, so the water and grit are confined. The dam can be putty, plasticine, clay, or other mouldable material put around the area to be drilled.
The grit can be sandblast grit or other abrasive of about 100 to 200 grit.
Drill as normal.
If the core gets stuck in the bit, knock it out with some stiff wire or a nail. Always remove each core right after drilling. They are very difficult to remove if there is more than one in the core of the bit.
For other tips on glass drilling see:
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits in glass
Drilling Glass 6
There are a variety of tools that can be used to power glass drills.
Dremmel and similar craft motorsThese are light duty high-speed drills. Those with variable speed controls are especially useful. They work best for small diameter holes. They must have the speed turned down for drilling, especially for larger holes.
These can be combined with a flexible drive shaft for lighter weight.
Drill pressHowever, the most important thing to have when drilling glass is a drill press. Doing it by hand is very difficult and wears out diamond bits very fast. Dremmel and others make drill presses for their tools.
Drilling machinesPurpose made glass-drilling machines are important for larger holes and production work. Flushing head adapters are available from suppliers that will convert a standard drill press into a glass-drilling machine. These tend to be much slower than the Dremmel style motors, but are very steady. The important thing about these is that they use hollow core drill bits, allowing the water to be fed through the drill bit directly to the glass-drilling site.
Drill bits
The other tool needed is drill bits. The recommended type depends on the size of hole to be drilled.
Small diameter holes, up to and including 3mm require solid bits. These can be spade (unusual) or solid diamond-tipped bits. A number of manufacturers make solid drill bits from 2-6mm and some (especially lapidary suppliers) make the very small diameter bits from less than 1mm to 2mm.
Larger diameter holes are best drilled with hollow core bits, as less glass needs to be removed to achieve the hole. These can be used with a flushing head or simply by directing water to the drill bit, with a dam to hold the water around the site.
The bits will last longer if you use a drill press. The press keeps the bit wobble to a minimum and maintains the vertical, both helping to reduce the wear on the bit.
Hollow core bits
Hollow core diamond bits are of two types:
One -where a heating process attaches the diamond - is called sintered in Europe and a number of other countries.
The second – where the diamond is bound to the metal with resins and other chemical attractions – is called bonded in Europe.
Bits of the first type are longer lasting and more expensive. These can be dressed with an aluminium oxide dressing stick to maintain their effectiveness.
Bits of the second type wear quickly and should not be dressed.
In general a diamond core drill breaks out much less glass at the bottom of the hole than a solid drill bit.
Water pumpA further tool that is useful to have is a re-circulating pump. This can be a small fountain pump with a flexible spout to aim the water on the drilling site. A foot switch can control the water flow. A large tub is required to act as the catch basin for the water that comes off the drill and as the reservoir for the pump.
For other tips on glass drilling see:
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling Speeds for diamond bits
Dremmel and similar craft motorsThese are light duty high-speed drills. Those with variable speed controls are especially useful. They work best for small diameter holes. They must have the speed turned down for drilling, especially for larger holes.
These can be combined with a flexible drive shaft for lighter weight.
Drill pressHowever, the most important thing to have when drilling glass is a drill press. Doing it by hand is very difficult and wears out diamond bits very fast. Dremmel and others make drill presses for their tools.
Drilling machinesPurpose made glass-drilling machines are important for larger holes and production work. Flushing head adapters are available from suppliers that will convert a standard drill press into a glass-drilling machine. These tend to be much slower than the Dremmel style motors, but are very steady. The important thing about these is that they use hollow core drill bits, allowing the water to be fed through the drill bit directly to the glass-drilling site.
Drill bits
The other tool needed is drill bits. The recommended type depends on the size of hole to be drilled.
Small diameter holes, up to and including 3mm require solid bits. These can be spade (unusual) or solid diamond-tipped bits. A number of manufacturers make solid drill bits from 2-6mm and some (especially lapidary suppliers) make the very small diameter bits from less than 1mm to 2mm.
Larger diameter holes are best drilled with hollow core bits, as less glass needs to be removed to achieve the hole. These can be used with a flushing head or simply by directing water to the drill bit, with a dam to hold the water around the site.
The bits will last longer if you use a drill press. The press keeps the bit wobble to a minimum and maintains the vertical, both helping to reduce the wear on the bit.
Hollow core bits
Hollow core diamond bits are of two types:
One -where a heating process attaches the diamond - is called sintered in Europe and a number of other countries.
The second – where the diamond is bound to the metal with resins and other chemical attractions – is called bonded in Europe.
Bits of the first type are longer lasting and more expensive. These can be dressed with an aluminium oxide dressing stick to maintain their effectiveness.
Bits of the second type wear quickly and should not be dressed.
In general a diamond core drill breaks out much less glass at the bottom of the hole than a solid drill bit.
Water pumpA further tool that is useful to have is a re-circulating pump. This can be a small fountain pump with a flexible spout to aim the water on the drilling site. A foot switch can control the water flow. A large tub is required to act as the catch basin for the water that comes off the drill and as the reservoir for the pump.
For other tips on glass drilling see:
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling Speeds for diamond bits
Drilling Glass, 7
Drilling glass without a drill press
It is best to have a drill press for drilling holes in glass, but there are ways of doing it with a hand drill.
Make a ring of modeling clay, plasticine, putty or other mouldable material about 5cm/2" in diameter and press it around the drill site. Fill the ring with water to cool the drill site and surrounding glass as well lubricate the drill bit. Buying sinered (more expensive) bits is worthwhile as they work much better than the cheaper resin bonded ones.
Use a paint pen to mark the spot where the hole is to be. Without a drill press, starting at an angle with a slow drill speed will stop the bit from sliding around as you establish the drilling point. As the glass surface is roughened, bring the drill to vertical. Move the drill up and down a little as you drill to allow the water into the hole. If you are using a solid or spade drill, a little oscillation keeps the bit from jamming in the hole. Do not do this with a core drill.
A Dremel running at top speed is way too fast. Slow it down with the speed control.
Every diameter drill bit has an optimum drill speed. The smaller the bit is, the faster the speed required.
For other tips on glass drilling see:
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits in glass
It is best to have a drill press for drilling holes in glass, but there are ways of doing it with a hand drill.
Make a ring of modeling clay, plasticine, putty or other mouldable material about 5cm/2" in diameter and press it around the drill site. Fill the ring with water to cool the drill site and surrounding glass as well lubricate the drill bit. Buying sinered (more expensive) bits is worthwhile as they work much better than the cheaper resin bonded ones.
Use a paint pen to mark the spot where the hole is to be. Without a drill press, starting at an angle with a slow drill speed will stop the bit from sliding around as you establish the drilling point. As the glass surface is roughened, bring the drill to vertical. Move the drill up and down a little as you drill to allow the water into the hole. If you are using a solid or spade drill, a little oscillation keeps the bit from jamming in the hole. Do not do this with a core drill.
A Dremel running at top speed is way too fast. Slow it down with the speed control.
Every diameter drill bit has an optimum drill speed. The smaller the bit is, the faster the speed required.
For other tips on glass drilling see:
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits in glass
Drilling glass, 8
Hole Placement
The general rule on drilling holes in glass is that the edge of the hole should be further away from the edge than the thickness of the glass. This means that the edge of the hole on a 6mm thick piece of glass must be more than 6mm from the edge of the glass.
The calculations are simple arithmetic.
Remember this is the minimum distance. For safety and durability in architectural or heavy circumstances, an additional margin must be added.
For other tips on glass drilling see:
Centering the drill bit
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits in glass
The general rule on drilling holes in glass is that the edge of the hole should be further away from the edge than the thickness of the glass. This means that the edge of the hole on a 6mm thick piece of glass must be more than 6mm from the edge of the glass.
The calculations are simple arithmetic.
- calculate the centre point of the hole by adding the radius of the hole to the thickness of the glass plus at least 1mm.
- For example, to drill a 10mm hole in 6mm glass, you add 5mm (radius of hole) to 6mm (thickness of the glass) plus 1mm = 12mm as the minimum distance from the edge of the glass to the centre of the hole.
Remember this is the minimum distance. For safety and durability in architectural or heavy circumstances, an additional margin must be added.
For other tips on glass drilling see:
Centering the drill bit
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits in glass
Drilling Glass, 9
Drilling speeds for diamond bits in glass
Diameter 3-4mm
Speed 6000 rpm
Diameter 5-8mm
Speed 4500 rpm
Diameter 9-12mm
Speed 3000 rpm
Diameter 13-16mm
Speed 2500 rpm
Diameter 17-25mm
Speed 2000 rpm
Diameter 26-28mm
Speed 1800 rpm
Diameter 29-44mm
Speed 1500 rpm
Diameter 45-64mm
Speed 1200 rpm
Diameter 65-89mm
Speed 900 rpm
Diameter 90-120mm
Speed 800 rpm
[Based on CR Lawrence and Amazing Glazing recommendations]
For other tips on glass drilling see:
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits in glass
Diameter 3-4mm
Speed 6000 rpm
Diameter 5-8mm
Speed 4500 rpm
Diameter 9-12mm
Speed 3000 rpm
Diameter 13-16mm
Speed 2500 rpm
Diameter 17-25mm
Speed 2000 rpm
Diameter 26-28mm
Speed 1800 rpm
Diameter 29-44mm
Speed 1500 rpm
Diameter 45-64mm
Speed 1200 rpm
Diameter 65-89mm
Speed 900 rpm
Diameter 90-120mm
Speed 800 rpm
[Based on CR Lawrence and Amazing Glazing recommendations]
For other tips on glass drilling see:
Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling speeds for diamond bits in glass
Saturday, 8 May 2010
Kiln Shelf Breakage
Placing moulds directly on shelves can cause breakage as my kiln keeps reminding me. If you put a mould directly onto the shelf, it apparently keeps the kiln from evenly heating the shelf on the way up and the mould keeps the shelf hotter than the edges on the way down. I don't know whether the shelf breaks on the way up -although I think that is so - or the way down. It doesn't happen every time, and that's why I forget.
It seems there is a critical relationship between the size of the shelf and the size of the piece covering the mould. The greater the proportion -up to some maximum, maybe 90% - the greater the likelihood of breakage it seems. A fully covered shelf would heat and cool along with the mould. When the mould is small in relation to the shelf, the heat can travel under the mould well enough to avoid breaking, it appears. It is the large range in between that causes the trouble.
A preventative is to fire without a shelf. But failing that possibility, raise the mould a little from the shelf with kiln furniture or pieces of thick fibre paper. Also keep the shelf elevated a little from the floor of the kiln.
It seems there is a critical relationship between the size of the shelf and the size of the piece covering the mould. The greater the proportion -up to some maximum, maybe 90% - the greater the likelihood of breakage it seems. A fully covered shelf would heat and cool along with the mould. When the mould is small in relation to the shelf, the heat can travel under the mould well enough to avoid breaking, it appears. It is the large range in between that causes the trouble.
A preventative is to fire without a shelf. But failing that possibility, raise the mould a little from the shelf with kiln furniture or pieces of thick fibre paper. Also keep the shelf elevated a little from the floor of the kiln.
Tuesday, 4 May 2010
Grinding to Shape
There are lots of ways people use to keep marks on the glass while grinding.
Paint markers will stand up to a lot of water if allowed to dry before being taken to the grinder.
Covering the marker line with Vaseline or lip salve will preserve the line longer.
Sticking down a water proof pattern piece on the glass will allow grinding up to the edges of the pattern piece without it breaking down. But of course, it can be ground away or pushed aside by the grinding head.
All these methods assume that there is a lot of grinding needed.
If you cut accurately, only a small amount of grinding will be needed and permanent felt tip/marker on glass lasts long enough to do the job.
Paint markers will stand up to a lot of water if allowed to dry before being taken to the grinder.
Covering the marker line with Vaseline or lip salve will preserve the line longer.
Sticking down a water proof pattern piece on the glass will allow grinding up to the edges of the pattern piece without it breaking down. But of course, it can be ground away or pushed aside by the grinding head.
All these methods assume that there is a lot of grinding needed.
If you cut accurately, only a small amount of grinding will be needed and permanent felt tip/marker on glass lasts long enough to do the job.
Friday, 30 April 2010
Rapid Heat Rises and Their Effects on Firings
Based on a communication from Phil Hoppes
A word of caution. Never use 9999 for a ramp up. Note: 9999 just means on an up ramp the elements are full on, no cycling. On the down ramp the power is completely off until the desired temperature is reached. Your kiln will rise in temperature limited by 2 things - the type of insulation and the number of elements. This can be anywhere from 300 – 450C/hr. to as high as 1600C/hr.)
If the time it takes to go from your lower temp to your upper temp is less than 40 minutes, your controller will be unable to accurately control the top temperature. For example, if you want to ramp from room temperature (20C) to 300C and for your kiln 9999 on an up ramp is 850C/hr., the temperature rise you are looking to accomplish is 280C and your kiln will reach 300C in just under 20 minutes. The problem is that most controllers need around 40 minutes in any ramp cycle to "learn" how the kiln is responding to the inputs that are given to it by the controller. Slower ramps need less “learning” time, faster ramps need more time.
What will happen if you programme a ramp shorter than your controller will respond to is that the temperature in your kiln will not stop nicely at the programmed 300C. The controller has not learned how to stop your kiln from rising in temperature yet and the temperature will rise much higher than your programmed value.
Depending on your kiln and your controller this can be quite significant. Most controllers have a peak shut off value, somewhere between 55C and 85C above your programmed amount. Some controllers allow you to program this value also. If the temperature in your kiln overshoots the value it was programmed to stop and the amount of overshoot exceeds the programmed shutoff temp your controller will shut down. This is a safety feature and the controller is doing what it is suppose to do. If you have something in your kiln however and this happens it will not be annealed properly and you will have to very carefully re-fire to remove the stress or it will break into pieces.
It is a good idea to know just what your kiln will do. You can do this by taking an empty kiln, program 9999 in an up ramp from room temp to 815C. This is the typical peak you would use in a full fuse. See how long it takes for your kiln to reach this temp. This will give you the maximum up ramp rate of your kiln. You can use this rate to calculate if you violate the “learning” margin of the controller.
It is advisable not to exceed 350C/hr up ramp unless overshooting the top temperature does not matter.
The 9999 ramp in almost all cases will be used to go from the top temperature to the start of the annealing cycle.
A word of caution. Never use 9999 for a ramp up. Note: 9999 just means on an up ramp the elements are full on, no cycling. On the down ramp the power is completely off until the desired temperature is reached. Your kiln will rise in temperature limited by 2 things - the type of insulation and the number of elements. This can be anywhere from 300 – 450C/hr. to as high as 1600C/hr.)
If the time it takes to go from your lower temp to your upper temp is less than 40 minutes, your controller will be unable to accurately control the top temperature. For example, if you want to ramp from room temperature (20C) to 300C and for your kiln 9999 on an up ramp is 850C/hr., the temperature rise you are looking to accomplish is 280C and your kiln will reach 300C in just under 20 minutes. The problem is that most controllers need around 40 minutes in any ramp cycle to "learn" how the kiln is responding to the inputs that are given to it by the controller. Slower ramps need less “learning” time, faster ramps need more time.
What will happen if you programme a ramp shorter than your controller will respond to is that the temperature in your kiln will not stop nicely at the programmed 300C. The controller has not learned how to stop your kiln from rising in temperature yet and the temperature will rise much higher than your programmed value.
Depending on your kiln and your controller this can be quite significant. Most controllers have a peak shut off value, somewhere between 55C and 85C above your programmed amount. Some controllers allow you to program this value also. If the temperature in your kiln overshoots the value it was programmed to stop and the amount of overshoot exceeds the programmed shutoff temp your controller will shut down. This is a safety feature and the controller is doing what it is suppose to do. If you have something in your kiln however and this happens it will not be annealed properly and you will have to very carefully re-fire to remove the stress or it will break into pieces.
It is a good idea to know just what your kiln will do. You can do this by taking an empty kiln, program 9999 in an up ramp from room temp to 815C. This is the typical peak you would use in a full fuse. See how long it takes for your kiln to reach this temp. This will give you the maximum up ramp rate of your kiln. You can use this rate to calculate if you violate the “learning” margin of the controller.
It is advisable not to exceed 350C/hr up ramp unless overshooting the top temperature does not matter.
The 9999 ramp in almost all cases will be used to go from the top temperature to the start of the annealing cycle.
Monday, 26 April 2010
Prevention of Needling in Dammed/ Box Cast Work
To avoid needling in box cast or dammed work you need to provide a space for the glass to flow into.
This is done by using 3mm thick fibre paper to line the damming materials. The fibre paper is cut to 3mm less than the finished height of the fired piece.
Fire the glass with a long bubble soak. This allows the glass to almost achieve its final height before it becomes less viscous. It will still be higher than the fibre paper and as the glass continues to be more “soft” it will round as it reaches full fusing temperature. There is not enough glass above the fibre – only 3mm – for the glass to run over the fibre, as the surface tension holds it in until 6 or 7mm above the fibre. The top edge of the glass does not touch the fibre or dam, so there are no needles.
Another way to avoid needles in this kind of work is to make the dams larger than the glass being contained. That is, place the dams a short distance away from the glass. The glass will then flow out to meet the dams. Since the glass is not contracting it will not have needles. This is a good solution when the thickness of the glass is not critical. You control the area of the piece by the placing of the dams.
This is done by using 3mm thick fibre paper to line the damming materials. The fibre paper is cut to 3mm less than the finished height of the fired piece.
Fire the glass with a long bubble soak. This allows the glass to almost achieve its final height before it becomes less viscous. It will still be higher than the fibre paper and as the glass continues to be more “soft” it will round as it reaches full fusing temperature. There is not enough glass above the fibre – only 3mm – for the glass to run over the fibre, as the surface tension holds it in until 6 or 7mm above the fibre. The top edge of the glass does not touch the fibre or dam, so there are no needles.
Another way to avoid needles in this kind of work is to make the dams larger than the glass being contained. That is, place the dams a short distance away from the glass. The glass will then flow out to meet the dams. Since the glass is not contracting it will not have needles. This is a good solution when the thickness of the glass is not critical. You control the area of the piece by the placing of the dams.
Saturday, 10 April 2010
Charging the Pot for a Melt
The way you charge (load the glass into) the pot makes a difference to the resulting piece.
A good way to get strong colour separation is to put two colours on opposite sides and a third colour or clear between them. The two side colours will have best separation if they are not more than 1/3 each. As the glass begins to flow out of the pot, all three colours will come out at once and form concentric circles (assuming a circular hole in the pot).
You can manipulate and alter the results with a fair amount of predictability by changing the diameter and shape of the hole, charging the pot with more than three colours or less, rearranging the orientation into a sunburst orientation or whatever comes to mind. Be sure to keep notes on what you did and what the results were in case you want to reproduce the effect.
Think about how the glass will flow out of the pot when you charge it with glass. If you layer colours horizontally from C (on top) to A (on bottom), it will initially flow out in colour A, then B, then C. After that initial flow, which will be on the outside of the finished piece, the main flow will be from the top (C), then the middle (B) and finally the bottom (A). This is because after the initial flow, the rest of the glass comes out in a funnel shape pulling the top and small portions of the underlying glass.
This means that layering is the best way of mixing colours. You need to think about colour combinations too. For example yellow and red become brown; yellow and blue a dark green, etc.
The proportion of dark colours is important, for example, as little as 2% of black can make the whole piece very dark. If you have dark colours, you need to add a large proportion of clear or very light opalescent glass.
If you use frit, large pieces are better than smaller ones. Even so, you need to be careful about the colours you use so the whole does not become muddy.
A good way to get strong colour separation is to put two colours on opposite sides and a third colour or clear between them. The two side colours will have best separation if they are not more than 1/3 each. As the glass begins to flow out of the pot, all three colours will come out at once and form concentric circles (assuming a circular hole in the pot).
 |
| Vertical stacking of multiple colours |
You can manipulate and alter the results with a fair amount of predictability by changing the diameter and shape of the hole, charging the pot with more than three colours or less, rearranging the orientation into a sunburst orientation or whatever comes to mind. Be sure to keep notes on what you did and what the results were in case you want to reproduce the effect.
Think about how the glass will flow out of the pot when you charge it with glass. If you layer colours horizontally from C (on top) to A (on bottom), it will initially flow out in colour A, then B, then C. After that initial flow, which will be on the outside of the finished piece, the main flow will be from the top (C), then the middle (B) and finally the bottom (A). This is because after the initial flow, the rest of the glass comes out in a funnel shape pulling the top and small portions of the underlying glass.
This means that layering is the best way of mixing colours. You need to think about colour combinations too. For example yellow and red become brown; yellow and blue a dark green, etc.
The proportion of dark colours is important, for example, as little as 2% of black can make the whole piece very dark. If you have dark colours, you need to add a large proportion of clear or very light opalescent glass.
If you use frit, large pieces are better than smaller ones. Even so, you need to be careful about the colours you use so the whole does not become muddy.
Tuesday, 6 April 2010
Aperture Pours
The most commonly used aperture pours are Pot melts and wire melts. Pot melts use containers, and wire mesh for wire melts. In both cases they control the way the glass melts into a container or directly on the shelf below.
The materials are stainless steel wire grids, and unglazed terracotta pots. The spacing of the steel grid will determine the number of trails of glass falling. So a finer grid will give more points of expansion in the resulting melt. But will mix the colours much more thoroughly than a coarser mesh will.
Doing a pot melt usually provides a simpler pattern of flow. A single round hole gives one circular point from which the glass expands. A single rectangular hole gives a single ribbon shape as the expansion point. You can, of course, have multiple holes in the bottom of the pot to provide a more complex interaction of the flowing glass. The wider the rim of the pot in relation to its depth, the more flexible it will be. You can put more glass in the pot and you can have it higher in the kiln.
The arrangement of glass in the pot will produce different results. There are two basic arrangements: colours layered one above each other as in a layer cake; and colours arranged on end around the sides of the pot. When loading the pot you need to remember that although the glass immediately above the hole will be the first to come out – and therefore be at the edge of the melt – the remainder of the glass comes out in a funnel-like order, with the glass at the bottom corner of the pot being the last to flow out – and become the centre of the melt.
There is a relationship between the hole size and distance to surface that affects the final appearance. The larger the hole the less likely the glass is to spiral as it falls, so you need a greater distance between the bottom of the pot and the shelf. The smaller the hole, the less distance you need. Only experience will tell you what distance and size you need or can use.
You can calculate the amount of glass for different sizes by using this table. If you have a rectangular space you are dropping into, you can calculate the volume of glass by multiplying the width, length and desired thickness – all in centimetres. This will give the volume in cubic centimetres and to convert that into weight, you multiply the volume by the specific gravity of glass - 2.5 is near enough – to get the number of grams of glass required. To convert into kilograms, divide by 1000.
By dropping directly onto kiln washed shelf, ring or circular container you will get some contamination. There are some ways to avoid this given here.
You can also use this method to act as a crucible to pour glass into closed moulds.
 |
| Emptied pot melt |
 |
| Finished screen melt |
Doing a pot melt usually provides a simpler pattern of flow. A single round hole gives one circular point from which the glass expands. A single rectangular hole gives a single ribbon shape as the expansion point. You can, of course, have multiple holes in the bottom of the pot to provide a more complex interaction of the flowing glass. The wider the rim of the pot in relation to its depth, the more flexible it will be. You can put more glass in the pot and you can have it higher in the kiln.
The arrangement of glass in the pot will produce different results. There are two basic arrangements: colours layered one above each other as in a layer cake; and colours arranged on end around the sides of the pot. When loading the pot you need to remember that although the glass immediately above the hole will be the first to come out – and therefore be at the edge of the melt – the remainder of the glass comes out in a funnel-like order, with the glass at the bottom corner of the pot being the last to flow out – and become the centre of the melt.
There is a relationship between the hole size and distance to surface that affects the final appearance. The larger the hole the less likely the glass is to spiral as it falls, so you need a greater distance between the bottom of the pot and the shelf. The smaller the hole, the less distance you need. Only experience will tell you what distance and size you need or can use.
You can calculate the amount of glass for different sizes by using this table. If you have a rectangular space you are dropping into, you can calculate the volume of glass by multiplying the width, length and desired thickness – all in centimetres. This will give the volume in cubic centimetres and to convert that into weight, you multiply the volume by the specific gravity of glass - 2.5 is near enough – to get the number of grams of glass required. To convert into kilograms, divide by 1000.
By dropping directly onto kiln washed shelf, ring or circular container you will get some contamination. There are some ways to avoid this given here.
You can also use this method to act as a crucible to pour glass into closed moulds.
Thursday, 18 March 2010
Pattern Scissors Usage
The purpose of pattern shears/scissors is to cut out the space between pattern pieces equivalent to the came heart or the space needed for foil.
The scissors come in two thicknesses – one for leaded and the thinner for copper foil.
If you must use them:Use in short cutting motions. Use only the first 50mm of the blades which are closest to the pivot point. Otherwise the paper jams in between the blades. It remains difficult to cut long straight lines without quickly having an “accordion” of paper blocking the cutting action.
Some suggestions to make things easier:
- Clean the blades regularly. If you are cutting anything with adhesives, clean the blades after each use with spirits.
- Often running a little soap along the blades helps to smooth the action of the blades.
- Use stiff high quality paper so you do not catch fibres in the scissors. Waxed paper or stencil card are good materials to use.
Organising pattern pieces.
- You have made a second and third copy of the cartoon haven’t you?
- Now that you have a lot of pieces what do you do with them?
- Mark any grain direction before you cut the pieces apart.
You need to code the pieces in some way.
- Numbering with reference to the main cartoon is most common.
- It is a good idea to colour code the pieces and if the surface will take it, a shading of the colour makes a quick visual reference.
Keeping the pieces together.
- Envelopes are easy to write on for colours, or areas such as borders, background, etc.
- Freezer bags that are transparent and have a band to write on are very good, as you can see the pieces without opening the bag.
- You need a labelled bag or container to keep all the envelopes together.
Alternatives to pattern scissors
- For copper foil, you can use normal scissors, by cutting to the inside of the pencil or inked line. - You can also use a scalpel or craft knife to cut to the insides of the marked lines.
- For leaded glass you can use a felt tip pen (a bullet point is almost exactly the right width when new). Cut with scissors or craft knife at the sides of the line.
Alternative to pattern piecesUse the European or trace cutting method as described here.
The scissors come in two thicknesses – one for leaded and the thinner for copper foil.
If you must use them:Use in short cutting motions. Use only the first 50mm of the blades which are closest to the pivot point. Otherwise the paper jams in between the blades. It remains difficult to cut long straight lines without quickly having an “accordion” of paper blocking the cutting action.
Some suggestions to make things easier:
- Clean the blades regularly. If you are cutting anything with adhesives, clean the blades after each use with spirits.
- Often running a little soap along the blades helps to smooth the action of the blades.
- Use stiff high quality paper so you do not catch fibres in the scissors. Waxed paper or stencil card are good materials to use.
Organising pattern pieces.
- You have made a second and third copy of the cartoon haven’t you?
- Now that you have a lot of pieces what do you do with them?
- Mark any grain direction before you cut the pieces apart.
You need to code the pieces in some way.
- Numbering with reference to the main cartoon is most common.
- It is a good idea to colour code the pieces and if the surface will take it, a shading of the colour makes a quick visual reference.
Keeping the pieces together.
- Envelopes are easy to write on for colours, or areas such as borders, background, etc.
- Freezer bags that are transparent and have a band to write on are very good, as you can see the pieces without opening the bag.
- You need a labelled bag or container to keep all the envelopes together.
Alternatives to pattern scissors
- For copper foil, you can use normal scissors, by cutting to the inside of the pencil or inked line. - You can also use a scalpel or craft knife to cut to the insides of the marked lines.
- For leaded glass you can use a felt tip pen (a bullet point is almost exactly the right width when new). Cut with scissors or craft knife at the sides of the line.
Alternative to pattern piecesUse the European or trace cutting method as described here.
Sunday, 14 March 2010
Removing Stick-on Lead and Film
It is possible to do this. It is a labour intensive process. You do need to be careful to avoid scratching the glass.
Cut through a lead line and carefully rip away the lead tape, being careful to not pull so hard that you flex the centre of the glass and cause it to break. You will need considerable force. The bulk of the lead is probably positioned over the film, so bulk of the the glue residue from the lead tape will come off when the film is peeled away. With a spray bottle mist the glass with white spirit and scrub using a cloth. If the glue is especially resistant use a broad wallpaper scraper and cover it with the kerosene soaked cloth to scrape the glue off. Use vinyl or latex gloves.
However, the manufacturer comments that stained glass overlay is virtually impossible to remove. It is better to replace the glass. It will save time, expense and possible tears.
Cut through a lead line and carefully rip away the lead tape, being careful to not pull so hard that you flex the centre of the glass and cause it to break. You will need considerable force. The bulk of the lead is probably positioned over the film, so bulk of the the glue residue from the lead tape will come off when the film is peeled away. With a spray bottle mist the glass with white spirit and scrub using a cloth. If the glue is especially resistant use a broad wallpaper scraper and cover it with the kerosene soaked cloth to scrape the glue off. Use vinyl or latex gloves.
However, the manufacturer comments that stained glass overlay is virtually impossible to remove. It is better to replace the glass. It will save time, expense and possible tears.
Saturday, 6 March 2010
Commissioning
Commissioning a stained glass window, screen or lamp involves entering into a contract with the designer/maker. It is therefore important that both client and maker know exactly what is involved.
· The price of the work should be established. The materials used in the making of a window, especially the glass itself, can be expensive and the possibility of commissioning a well-designed leaded light should not be ignored.
· The maker will need to know the budget for the work and will provide an estimate, and may require a down payment before beginning work and perhaps payment by instalments, depending upon the cost of the materials involved.
The designer will prepare a preliminary design, according to the client's brief.
· The design should indicate the nature of the construction and the position of any ferramenta or physical support.
· This design should be as detailed as possible. It may be accompanied by samples of the proposed glasses.
· The client must be prepared to recompense an artist for design(s) prepared according to a brief, whether or not it proceeds to execution.
· The copyright in all cases remains the property of the artist.
The arrangements for the execution of the commission must also be satisfactorily established, including those for installation. If necessary, the advice of an architect should be sought; for church commissions, the architect responsible for the church should be involved from the outset. If the window is to be sited in an exposed position or in an area where vandalism is known to be a problem, protective measures should be considered.
Also look at Commission Agreements
· The price of the work should be established. The materials used in the making of a window, especially the glass itself, can be expensive and the possibility of commissioning a well-designed leaded light should not be ignored.
· The maker will need to know the budget for the work and will provide an estimate, and may require a down payment before beginning work and perhaps payment by instalments, depending upon the cost of the materials involved.
The designer will prepare a preliminary design, according to the client's brief.
· The design should indicate the nature of the construction and the position of any ferramenta or physical support.
· This design should be as detailed as possible. It may be accompanied by samples of the proposed glasses.
· The client must be prepared to recompense an artist for design(s) prepared according to a brief, whether or not it proceeds to execution.
· The copyright in all cases remains the property of the artist.
The arrangements for the execution of the commission must also be satisfactorily established, including those for installation. If necessary, the advice of an architect should be sought; for church commissions, the architect responsible for the church should be involved from the outset. If the window is to be sited in an exposed position or in an area where vandalism is known to be a problem, protective measures should be considered.
Also look at Commission Agreements
Tuesday, 2 March 2010
Effect of Plaster-Water Ratio on Some Properties
Plaster-water ratio (by weight) 100/30
Setting time (min) 1.75
Compression strength (kg/sq.cm) 808
Dry Density (kg/cu metre) 1806
Plaster-water ratio (by weight) 100/40
Setting time (min) 3.25
Compression strength (kg/sq.cm)474
Dry Density (kg/cu metre) 1548
Plaster-water ratio (by weight) 100/50
Setting time (min) 5.25
Compression strength (kg/sq.cm)316
Dry Density (kg/cu metre) 1352
Plaster-water ratio (by weight) 100/60
Setting time (min) 7.24
Compression strength (kg/sq.cm)228
Dry Density (kg/cu metre) 1206
Plaster-water ratio (by weight) 100/70
Setting time (min) 8.25
Compression strength (kg/sq.cm)175
Dry Density (kg/cu metre) 1083
Plaster-water ratio (by weight) 100/80
Setting time (min) 10.50
Compression strength (kg/sq.cm)126
Dry Density (kg/cu metre) 990
Plaster-water ratio (by weight) 100/90
Setting time (min) 12.00
Compression strength (kg/sq.cm)98
Dry Density (kg/cu metre) 908
Plaster-water ratio (by weight) 100/100
Setting time (min) 13.75
Compression strength (kg/sq.cm) 70
Dry Density (kg/cu metre) 867
This table of relationships makes it clear that the less weight of water added to the plaster, the stronger the resulting mould will be. It also is clear that with less water, the setting time is reduced. So some compromise may be needed to be able to pour the mixture before it sets.
Setting time (min) 1.75
Compression strength (kg/sq.cm) 808
Dry Density (kg/cu metre) 1806
Plaster-water ratio (by weight) 100/40
Setting time (min) 3.25
Compression strength (kg/sq.cm)474
Dry Density (kg/cu metre) 1548
Plaster-water ratio (by weight) 100/50
Setting time (min) 5.25
Compression strength (kg/sq.cm)316
Dry Density (kg/cu metre) 1352
Plaster-water ratio (by weight) 100/60
Setting time (min) 7.24
Compression strength (kg/sq.cm)228
Dry Density (kg/cu metre) 1206
Plaster-water ratio (by weight) 100/70
Setting time (min) 8.25
Compression strength (kg/sq.cm)175
Dry Density (kg/cu metre) 1083
Plaster-water ratio (by weight) 100/80
Setting time (min) 10.50
Compression strength (kg/sq.cm)126
Dry Density (kg/cu metre) 990
Plaster-water ratio (by weight) 100/90
Setting time (min) 12.00
Compression strength (kg/sq.cm)98
Dry Density (kg/cu metre) 908
Plaster-water ratio (by weight) 100/100
Setting time (min) 13.75
Compression strength (kg/sq.cm) 70
Dry Density (kg/cu metre) 867
This table of relationships makes it clear that the less weight of water added to the plaster, the stronger the resulting mould will be. It also is clear that with less water, the setting time is reduced. So some compromise may be needed to be able to pour the mixture before it sets.
Saturday, 27 February 2010
Properties of typical gypsum plasters and cements
Number 1 Pottery Plaster
% of water to dry mix by weight - 70%
Set Time – 27 – 37 mins
Dry density – 1105 kg/cubic metre
Expansion on setting – 0.21%
Compressive strength - 126 kg./square centimeter
No. 1 Casting plaster% of water to dry mix by weight - 70%
Set Time – 27 – 37 mins
Dry density – 1058 kg/cubic metre
Expansion on setting – 0.2%
Compressive strength - 140 kg./square centimeter
Plaster of Paris% of water to dry mix by weight - 70%
Set Time – 27 – 37 mins
Dry density – 1105 kg/cubic metre
Expansion on setting – 0.2%
Compressive strength - 140 kg./square centimeter
Number 1 Casting Plaster% of water to dry mix by weight - 65%
Set Time – 27 – 37 mins
Dry density – 1162 kg/cubic metre
Expansion on setting – 0.22%
Compressive strength - 168 kg./square centimeter
Pottery Plaster
% of water to dry mix by weight - 74%
Set Time – 27 – 37 mins
Dry density – 1162 kg/cubic metre
Expansion on setting – 0.19%
Compressive strength - 126 kg./square centimeter
Hydrocal Cement
% of water to dry mix by weight - 45%
Set Time – 25 – 35 mins
Dry density – 1442 kg/cubic metre
Expansion on setting – 0.39%
Compressive strength – 35 kg./square centimeter
Hydroperm Cement% of water to dry mix by weight - 10%
Set Time – 12 -19 mins
Dry density –
<641 br="" cubic="" kg="" metre="">Expansion on setting – 0.14%
Compressive strength – 35 kg./square centimeter
Hydro-Stone cement
% of water to dry mix by weight - 32%
Set Time – 17 -20 mins
Dry density – 1913 kg/cubic metre
Expansion on setting – 0.24%
Compressive strength – 703 kg./square centimeter
Ultracal cement
% of water to dry mix by weight - 38%
Set Time – 25 - 35 mins
Dry density – 1568 kg/cubic metre
Expansion on setting – 0.08%
Compressive strength – 421 kg./square centimeter
% of water to dry mix by weight - 70%
Set Time – 27 – 37 mins
Dry density – 1105 kg/cubic metre
Expansion on setting – 0.21%
Compressive strength - 126 kg./square centimeter
No. 1 Casting plaster% of water to dry mix by weight - 70%
Set Time – 27 – 37 mins
Dry density – 1058 kg/cubic metre
Expansion on setting – 0.2%
Compressive strength - 140 kg./square centimeter
Plaster of Paris% of water to dry mix by weight - 70%
Set Time – 27 – 37 mins
Dry density – 1105 kg/cubic metre
Expansion on setting – 0.2%
Compressive strength - 140 kg./square centimeter
Number 1 Casting Plaster% of water to dry mix by weight - 65%
Set Time – 27 – 37 mins
Dry density – 1162 kg/cubic metre
Expansion on setting – 0.22%
Compressive strength - 168 kg./square centimeter
Pottery Plaster
% of water to dry mix by weight - 74%
Set Time – 27 – 37 mins
Dry density – 1162 kg/cubic metre
Expansion on setting – 0.19%
Compressive strength - 126 kg./square centimeter
Hydrocal Cement
% of water to dry mix by weight - 45%
Set Time – 25 – 35 mins
Dry density – 1442 kg/cubic metre
Expansion on setting – 0.39%
Compressive strength – 35 kg./square centimeter
Hydroperm Cement% of water to dry mix by weight - 10%
Set Time – 12 -19 mins
Dry density –
<641 br="" cubic="" kg="" metre="">Expansion on setting – 0.14%
Compressive strength – 35 kg./square centimeter
Hydro-Stone cement
% of water to dry mix by weight - 32%
Set Time – 17 -20 mins
Dry density – 1913 kg/cubic metre
Expansion on setting – 0.24%
Compressive strength – 703 kg./square centimeter
Ultracal cement
% of water to dry mix by weight - 38%
Set Time – 25 - 35 mins
Dry density – 1568 kg/cubic metre
Expansion on setting – 0.08%
Compressive strength – 421 kg./square centimeter
Tuesday, 23 February 2010
Break Down Temperatures of Common Mould Constituents
Binders are essential parts of mould materials. They hold the refractory parts of the mould together. Selection is dependent on the temperature you will be using. This also is important in choosing the refractory material to use.
Gypsum plaster - 704C – 816C
Hydrocal cement - 704C – 816C
Hydroperm cement – 760C – 927C
Colloidal silica – 1260C
Colloidal alumina – 1260C
Calcium alumina cement (cement fondu) – 1538C
There are of course, many other factors to take into account when choosing binders and refractory materials for moulds.
Gypsum plaster - 704C – 816C
Hydrocal cement - 704C – 816C
Hydroperm cement – 760C – 927C
Colloidal silica – 1260C
Colloidal alumina – 1260C
Calcium alumina cement (cement fondu) – 1538C
There are of course, many other factors to take into account when choosing binders and refractory materials for moulds.
Friday, 19 February 2010
Temperature Characteristics of Various Glasses
Over the years I have collected temperature information for a number of glasses. They are of comparative interest and can assist with choosing a temperature or range of temperatures for the work you are doing. If the work is important, or critical, refer to the manufacturer for the latest information.
Bullseye
There has been a lot of information published about this glass. One interesting characteristic has been the different temperatures for the complete range of glass they produce. So there appears to be a difference between the transparent, opalescent and gold pink glasses.
Transparent:
Full Fusing 832C ; Tack Fusing 777C ; Softening 677C ; Annealing 532C ; Strain 493C
Opalescent:
Full Fusing 843C ; Tack Fusing 788C ; Softening 688C ; Annealing 502C ; Strain 463C
Gold Bearing:
Full Fusing 788C ; Tack Fusing 732C ; Softening 635C ; Annealing 472C ; Strain 438C
This also illustrates that not all the characteristics of a glass range are linear. The most apparent one is that the full fusing, tack fusing and softening points of the opalescent glass are higher than transparent, although the annealing point is lower.
Desag GNA
Full Fusing 857C ; Tack Fusing 802C ; Softening 718C ; Annealing 516C ; Strain 427C
Float Glass
Full Fusing 835C ; Tack Fusing ca. 760C ; Softening 720C ; Annealing ca. 530C ; Strain 454
Spectrum S96
Full Fusing 788C ; Tack Fusing 718C ; Softening 677C ; Annealing 510C ; Strain 371C
Uroboros
Full Fusing 788C ; Tack Fusing 732C ; Softening 663C ; Annealing 538C ; Strain 427C
Although the information above may be dated, the important element is that there is little correlation between glasses in the relationship of annealing point to other characteristics of the glass.
This listing also shows that the temperature characteristics are not linear between glasses. For example, Spectrum and Uroboros have the same full fuse temperatures, but different tack fusing, softening, annealing and strain temperatures. Sometimes one is higher than the other, and other times it is reversed.
Another example is shown by the Desag GNA and Float glasses. Desag GNA has higher full fuse and tack fuse temperatures than float, but lower softening, annealing and strain temperatures. This helps to make the point that you need to know the glass you are using as it will not have a proportional relationship at every point in the kiln working temperature range.
I emphasise that these temperatures have been collected over a period and may not be the current or absolutely correct information. They are used here to illustrate the differences within and between the glasses of various manufacturers.
Bullseye
There has been a lot of information published about this glass. One interesting characteristic has been the different temperatures for the complete range of glass they produce. So there appears to be a difference between the transparent, opalescent and gold pink glasses.
Transparent:
Full Fusing 832C ; Tack Fusing 777C ; Softening 677C ; Annealing 532C ; Strain 493C
Opalescent:
Full Fusing 843C ; Tack Fusing 788C ; Softening 688C ; Annealing 502C ; Strain 463C
Gold Bearing:
Full Fusing 788C ; Tack Fusing 732C ; Softening 635C ; Annealing 472C ; Strain 438C
This also illustrates that not all the characteristics of a glass range are linear. The most apparent one is that the full fusing, tack fusing and softening points of the opalescent glass are higher than transparent, although the annealing point is lower.
Desag GNA
Full Fusing 857C ; Tack Fusing 802C ; Softening 718C ; Annealing 516C ; Strain 427C
Float Glass
Full Fusing 835C ; Tack Fusing ca. 760C ; Softening 720C ; Annealing ca. 530C ; Strain 454
Spectrum S96
Full Fusing 788C ; Tack Fusing 718C ; Softening 677C ; Annealing 510C ; Strain 371C
Uroboros
Full Fusing 788C ; Tack Fusing 732C ; Softening 663C ; Annealing 538C ; Strain 427C
Although the information above may be dated, the important element is that there is little correlation between glasses in the relationship of annealing point to other characteristics of the glass.
This listing also shows that the temperature characteristics are not linear between glasses. For example, Spectrum and Uroboros have the same full fuse temperatures, but different tack fusing, softening, annealing and strain temperatures. Sometimes one is higher than the other, and other times it is reversed.
Another example is shown by the Desag GNA and Float glasses. Desag GNA has higher full fuse and tack fuse temperatures than float, but lower softening, annealing and strain temperatures. This helps to make the point that you need to know the glass you are using as it will not have a proportional relationship at every point in the kiln working temperature range.
I emphasise that these temperatures have been collected over a period and may not be the current or absolutely correct information. They are used here to illustrate the differences within and between the glasses of various manufacturers.
Monday, 15 February 2010
Mesh Sizes
Mesh and grit sizes are most often refered to by a number. This relates to the number of wires per inch - and in a subsidary fashion also to the size of the wire used to form the grid through which the material falls and so is sorted into various sizes. The table below gives some of these figures most useful for mould making - mesh number, percentage of open area, the wire diameters in mm, and the mesh opening or material size in mm.
No.12 ; % open 51.8 ; dia. 0.5842 ; size 1.5240
No.14 ; % open 51.0 ;dia. 0.5080 ; size 1.2954
No.20 ; % open 46.2 ; dia. 0.4064 ; size 0.8636
No.30 ; % open 37.1 ; dia. 0.3048 ; size 0.5156
No.40 ; % open 36.0 ; dia. 0.2286 ; size 0.3810
No.50 ; % open 30.3 ; dia. 0.1905 ; size 0.2794
No.60 ; % open 30.5 ; dia. 0.1397 ; size 0.2337
No.80 ; % open 31.4 ; dia. 0.1143 ; size 0.1778
No.100;% open 30.3 ; dia. 0.0940 ; size 0.1397
No.120; % open 30.7 ; dia. 0.0940 ; size 0.1168
No.200; % open 33.6 ; dia. 0.0533 ; size 0.0737
No.325;% open 30.0 ; dia. 0.0356 ; size 0.0432
No.12 ; % open 51.8 ; dia. 0.5842 ; size 1.5240
No.14 ; % open 51.0 ;dia. 0.5080 ; size 1.2954
No.20 ; % open 46.2 ; dia. 0.4064 ; size 0.8636
No.30 ; % open 37.1 ; dia. 0.3048 ; size 0.5156
No.40 ; % open 36.0 ; dia. 0.2286 ; size 0.3810
No.50 ; % open 30.3 ; dia. 0.1905 ; size 0.2794
No.60 ; % open 30.5 ; dia. 0.1397 ; size 0.2337
No.80 ; % open 31.4 ; dia. 0.1143 ; size 0.1778
No.100;% open 30.3 ; dia. 0.0940 ; size 0.1397
No.120; % open 30.7 ; dia. 0.0940 ; size 0.1168
No.200; % open 33.6 ; dia. 0.0533 ; size 0.0737
No.325;% open 30.0 ; dia. 0.0356 ; size 0.0432
Thursday, 11 February 2010
Properties of Some Basic Glass Types
Various types of glass have differing properties which make them suitable for a variety of applications. Some of the characteristics of three glasses are given here. The glasses are quartz, soda/lime, and lead crystal.
Quartz glass
Softening point (C) 1508
Annealing point (C) 1048
Strain point (C) 956
CoE at 10-7 metres/degree C: 3.1
Density (kg/m3) 1973
Refractive index 1.459
Soda/Lime glass
Softening point (C) 693 - 732
Annealing point (C) 516 - 549
Strain point (C) 471 - 493
CoE at 10-7 metres/degree C: 56 - 100
Density (kg/m3) 2203 - 2275
Refractive index 1.51 – 1.52
Lead glass
Softening point (C) 438 - 671
Annealing point (C) 366 - 527
Strain point (C) 343 - 449
CoE at 10-7 metres/degree C: 47 - 55
Density (kg/m3) 2505 - 4867
Refractive index 1.54 – 1.75
Quartz glass
Softening point (C) 1508
Annealing point (C) 1048
Strain point (C) 956
CoE at 10-7 metres/degree C: 3.1
Density (kg/m3) 1973
Refractive index 1.459
Soda/Lime glass
Softening point (C) 693 - 732
Annealing point (C) 516 - 549
Strain point (C) 471 - 493
CoE at 10-7 metres/degree C: 56 - 100
Density (kg/m3) 2203 - 2275
Refractive index 1.51 – 1.52
Lead glass
Softening point (C) 438 - 671
Annealing point (C) 366 - 527
Strain point (C) 343 - 449
CoE at 10-7 metres/degree C: 47 - 55
Density (kg/m3) 2505 - 4867
Refractive index 1.54 – 1.75
Friday, 15 January 2010
Creating a Quality Solder Joint
Soldering is the process that uses solder (a metal alloy usually consisting of tin mixed with other metals) for the metallurgical joining of metal components to form an electrical, mechanical or hermetically sealed bond at temperatures (less than 449°C) that are well below the melting temperature of the individual components that are being joined. The soldering equipment (used to create the required heat) and other materials (solder, fluxes, heat sinks, fixtures, etc.) should always be properly matched to the intended soldering application. The equipment and materials used may vary, but the basic soldering techniques that are required will usually remain the same.
One of the most important rules to remember about soldering is "keep it clean". This includes, not only the items being soldered, but also the materials used. Choose quality solders and fluxes without unnecessary impurities. Surface oxidation, contaminants and other impurities are some of the most common reasons for poor quality solder joints. The use of fluxes does not eliminate the need for pre-cleaning the surfaces you are joining, especially if heavy oxidation or large amounts of grease, oil or dirt are present.
1. Clean: Thoroughly clean all surfaces to be joined, removing any dirt, grease, oil, oxidation, paint, coatings or other impurities that may exist before attempting to solder. Proper wetting can only occur when the intended solder joint area has been properly cleaned. Soldering should be performed as soon as possible after cleaning to eliminate the possibility of re oxidation or contamination of the items being soldered. [So leaving pieces fluxed overnight is not good practice. Flux only the area that can be soldered in the next few minutes.]
2. Flux: Apply flux sparingly to each of the intended joint surfaces. Flux is primarily used for the removal of light oxidation and to protect against re-oxidation during the actual soldering process. Make sure you have the right flux for the application being performed.
3. Heat: Apply heat directly to the intended joint area. The correct application of heat is important and should be consistent with the operating requirements determined by the type of equipment being used. Fast and accurate heating will minimize the risk of thermal damage.
4. Solder: Add solder to the heated surfaces you are joining (do not apply solder directly to the tip, or other heat source being used). The solder should flow uniformly over all of the surfaces that are being connected. Stop feeding solder as soon as you have applied an adequate amount and then remove the heat source. The amount of solder is important because too much will create unnecessary waste, while too little can affect the mechanical strength and conductivity of the finished solder joint.
5. Cool: Allow the finished solder joint to remain undisturbed until it has completely cooled. You should never attempt to speed up the cooling process by blowing on the solder joint. Even minor vibrations or disturbances during cooling, can cause micro fractures or other types of damage that may severely weaken the solder joint.
6. Inspect: Check all finished joints for proper wetting, the right amount of solder, a good physical appearance, and the required mechanical strength.
SkillsA quality solder joint is not achieved solely by the equipment and techniques being used, but also by the operator being trained to use them properly. An operator should know how the physical appearance of a finished solder joint helps to determine possible flaws that may exist.
A quality solder joint appears bright, shiny and smooth with all components appearing well soldered. The surface of a finished connection should never look rough, grainy, dull, or flaky (these are signs of what is commonly referred to as a cold solder joint). Problems with proper wetting (solder balling up and not adhering to the components surface) are sometimes associated with too much heat, but are more often related to cleanliness issues.
Courtesy of American Beauty Tools
One of the most important rules to remember about soldering is "keep it clean". This includes, not only the items being soldered, but also the materials used. Choose quality solders and fluxes without unnecessary impurities. Surface oxidation, contaminants and other impurities are some of the most common reasons for poor quality solder joints. The use of fluxes does not eliminate the need for pre-cleaning the surfaces you are joining, especially if heavy oxidation or large amounts of grease, oil or dirt are present.
1. Clean: Thoroughly clean all surfaces to be joined, removing any dirt, grease, oil, oxidation, paint, coatings or other impurities that may exist before attempting to solder. Proper wetting can only occur when the intended solder joint area has been properly cleaned. Soldering should be performed as soon as possible after cleaning to eliminate the possibility of re oxidation or contamination of the items being soldered. [So leaving pieces fluxed overnight is not good practice. Flux only the area that can be soldered in the next few minutes.]
2. Flux: Apply flux sparingly to each of the intended joint surfaces. Flux is primarily used for the removal of light oxidation and to protect against re-oxidation during the actual soldering process. Make sure you have the right flux for the application being performed.
3. Heat: Apply heat directly to the intended joint area. The correct application of heat is important and should be consistent with the operating requirements determined by the type of equipment being used. Fast and accurate heating will minimize the risk of thermal damage.
4. Solder: Add solder to the heated surfaces you are joining (do not apply solder directly to the tip, or other heat source being used). The solder should flow uniformly over all of the surfaces that are being connected. Stop feeding solder as soon as you have applied an adequate amount and then remove the heat source. The amount of solder is important because too much will create unnecessary waste, while too little can affect the mechanical strength and conductivity of the finished solder joint.
5. Cool: Allow the finished solder joint to remain undisturbed until it has completely cooled. You should never attempt to speed up the cooling process by blowing on the solder joint. Even minor vibrations or disturbances during cooling, can cause micro fractures or other types of damage that may severely weaken the solder joint.
6. Inspect: Check all finished joints for proper wetting, the right amount of solder, a good physical appearance, and the required mechanical strength.
SkillsA quality solder joint is not achieved solely by the equipment and techniques being used, but also by the operator being trained to use them properly. An operator should know how the physical appearance of a finished solder joint helps to determine possible flaws that may exist.
A quality solder joint appears bright, shiny and smooth with all components appearing well soldered. The surface of a finished connection should never look rough, grainy, dull, or flaky (these are signs of what is commonly referred to as a cold solder joint). Problems with proper wetting (solder balling up and not adhering to the components surface) are sometimes associated with too much heat, but are more often related to cleanliness issues.
Courtesy of American Beauty Tools
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