Dams can be of any height available, but if it is easy to adjust the height, you should consider the ease of working with the glass inside the dams and the possibility of anything falling off the dams onto the glass.
The dam should be higher than the glass in its un-fired state. It should be high enough to contain the moving glass should anything go wrong, so it cannot be the same height as the fibre paper liners – those being 3mm shorter than the glass is high. As a rule of thumb, when I have the choice, I would make the dams at least 6mm higher than the unfired glass. This allows you to handle the sheets of glass and any components without having to reach over high walls. It also ensures containment should anything go wrong.
Wednesday, 8 September 2010
Saturday, 4 September 2010
Damming Irregular Shapes
The assumption is that these pieces will be open-face thick fusings/castings rather than enclosed castings.
There are two basic types of dams: a shape cut from a single surrounding piece, or multiple pieces held in place.
Single piece dams
A large, thick fibre board with shape cut out will confine the glass. If very thick, you may need to weight the fibre board, as it is lighter than the glass.
Another variation is to use thick fibre paper cut out to shape and layered up to the desired height with stainless steel pins to hold the whole in place. This also may need to be weighted down. A variation on this is to place the whole on a fibre board and pin the layers of fibre paper into the fibre board to maintain the position of the fibre dams. This will not normally need weighting.
Multiple piece dams
If the shapes are not extreme, you can use pieces of fibre board or fibre paper backed up with kiln furniture, bits of broken kiln shelf or any other heavy material that will withstand the heat of fusing.
You can use thick fibre paper held in place with kiln furniture, if the piece is not thick. You do have to be careful that the glass does not float the fibre paper and run underneath, so about 10 mm is the maximum for this kind of damming. It also helps if this kind of dam is made larger than the glass – or alternatively the glass smaller than the dam. This allows the glass to flow out toward the dam, giving nice curved edges.
Moulds, stainless steel and other refractory materials can be specially made for shapes that will be repeated.
Note that all these variations will benefit from being lined with Thinfire backed up with fibre paper. This gives a smoother edge and also gives some cusioning between the dam and the glass.
There are two basic types of dams: a shape cut from a single surrounding piece, or multiple pieces held in place.
Single piece dams
A large, thick fibre board with shape cut out will confine the glass. If very thick, you may need to weight the fibre board, as it is lighter than the glass.
Another variation is to use thick fibre paper cut out to shape and layered up to the desired height with stainless steel pins to hold the whole in place. This also may need to be weighted down. A variation on this is to place the whole on a fibre board and pin the layers of fibre paper into the fibre board to maintain the position of the fibre dams. This will not normally need weighting.
Multiple piece dams
If the shapes are not extreme, you can use pieces of fibre board or fibre paper backed up with kiln furniture, bits of broken kiln shelf or any other heavy material that will withstand the heat of fusing.
You can use thick fibre paper held in place with kiln furniture, if the piece is not thick. You do have to be careful that the glass does not float the fibre paper and run underneath, so about 10 mm is the maximum for this kind of damming. It also helps if this kind of dam is made larger than the glass – or alternatively the glass smaller than the dam. This allows the glass to flow out toward the dam, giving nice curved edges.
Moulds, stainless steel and other refractory materials can be specially made for shapes that will be repeated.
Note that all these variations will benefit from being lined with Thinfire backed up with fibre paper. This gives a smoother edge and also gives some cusioning between the dam and the glass.
Monday, 30 August 2010
Coating Metal Moulds
Most metal moulds are stainless steel as it spalls less while at forming temperatures. The techniques here can be applied to any metal, although spalling will be a common occurrence on any metal other than high grade stainless steel.
On many single curve moulds, such as a partial cylinder, you can just lay fibre paper over the form and place the glass on top of that.
Metal moulds that have more complex shapes require a separator that will conform to those shapes. Applying liquid kiln wash requires you to heat the steel to somewhere between 150 and 200C before applying the kiln wash. Any hotter and the kiln wash will boil off on contact, leaving an uneven coating.
The kiln wash can be applied with a brush or by spraying. Spraying gives a smoother less streaky application. After giving the mould the first coat, return the mould to the kiln and re-heat the mould. Repeat this until you have covered the whole mould with a thin layer of separator. Be careful and avoid applying too much kiln wash at once, as that will cause the separator to run and reveal bare spots on the mould, causing you to need to clean and begin again.
On many single curve moulds, such as a partial cylinder, you can just lay fibre paper over the form and place the glass on top of that.
Metal moulds that have more complex shapes require a separator that will conform to those shapes. Applying liquid kiln wash requires you to heat the steel to somewhere between 150 and 200C before applying the kiln wash. Any hotter and the kiln wash will boil off on contact, leaving an uneven coating.
The kiln wash can be applied with a brush or by spraying. Spraying gives a smoother less streaky application. After giving the mould the first coat, return the mould to the kiln and re-heat the mould. Repeat this until you have covered the whole mould with a thin layer of separator. Be careful and avoid applying too much kiln wash at once, as that will cause the separator to run and reveal bare spots on the mould, causing you to need to clean and begin again.
Thursday, 26 August 2010
Cleaning Glass
Glass with dust, oil or other residues promotes devitrification. So first try to remove any excess of these.
Cutting without oil can avoid introducing more oils. Specially formulated cuttings fluids are available that are not oil.
Wash with only a few drops of washing up liquid of the kind without additives to keep you hands soft, or smell good. If there are soap bubbles on top of the water, you are using too much soap.
Window cleaning products are not usually appropriate, especially if they contain ammonia. A few products do not have additives that promote devitrification. One that works well for me is the Bohle aerosol cleaner (but not the concentrate).
Be careful about your rinsing water. If it has mineral salts in it, it can form nucleation points for devit.
Polish dry using plain paper towels or microfiber cloths. Change frequently and wash without softeners.
If you are grinding the edges, clean immediately before any part dries to avoid the powdered glass filling the scratches caused by grinding. Some put the ground pieces into a bowl of water immediately to keep the edges wet until cleaning can be done.
Cutting without oil can avoid introducing more oils. Specially formulated cuttings fluids are available that are not oil.
Wash with only a few drops of washing up liquid of the kind without additives to keep you hands soft, or smell good. If there are soap bubbles on top of the water, you are using too much soap.
Window cleaning products are not usually appropriate, especially if they contain ammonia. A few products do not have additives that promote devitrification. One that works well for me is the Bohle aerosol cleaner (but not the concentrate).
Be careful about your rinsing water. If it has mineral salts in it, it can form nucleation points for devit.
Polish dry using plain paper towels or microfiber cloths. Change frequently and wash without softeners.
If you are grinding the edges, clean immediately before any part dries to avoid the powdered glass filling the scratches caused by grinding. Some put the ground pieces into a bowl of water immediately to keep the edges wet until cleaning can be done.
Sunday, 22 August 2010
Moving Pieces
To keep pieces from moving about as you solder them, use pins or nails to keep them in place. The best is to assemble the whole panel and then keep them in place with a frame or lots of nails/pins around the outside. This keeps pieces from moving and also keeps the panel to the original size.
The type of nail or pin will depend on the work board you are using. Softer boards allow push pins of various sorts to be used. Harder boards will need nails.
If you don’t like assembling the whole before soldering, you can confine the pieces you are currently soldering with nails/pins in the same fashion as for the whole panel.
It also helps to do a little tack soldering before the process of running a bead begins. A small amount of solder on the copper foil where pieces join will keep the pieces in exact alignment while you are running a bead.
The type of nail or pin will depend on the work board you are using. Softer boards allow push pins of various sorts to be used. Harder boards will need nails.
If you don’t like assembling the whole before soldering, you can confine the pieces you are currently soldering with nails/pins in the same fashion as for the whole panel.
It also helps to do a little tack soldering before the process of running a bead begins. A small amount of solder on the copper foil where pieces join will keep the pieces in exact alignment while you are running a bead.
Wednesday, 18 August 2010
Devitrification of Edges
Devitrification often occurs on the edges of glass, and can be seen as a thin line of devitrification -often looking like smudges that won't wipe off - where the edge has flattened during the fusing. There are some ways to avoid this.
Avoid grinding if at all possible.
If you must grind, use fine heads/grits. Then clean immediately before any part of the glass dries. You may need to clean part of the glass piece before the grinding is complete to avoid any drying of the powder on the edge of the glass.
Clean well with a minimum of soap and rinse with water that does not have a lot of minerals in it. Polish well with plain paper towels or frequently changed microfiber cloths.
Window cleaning products are not usually appropriate, especially if they contain ammonia.
Avoid introducing oils from the cutter by scoring with a dry cutter or use a specially devised cutting fluid. Cleaning solutions that have additives to be kind to hands or scents should be avoided.
The edges of some glasses devitrify more easily than others. If this continues to be the case after all cleaning efforts have failed, then use a devitrification spray, but continued cleaning is still necessary. There are no short cuts in cleaning.
Avoid grinding if at all possible.
If you must grind, use fine heads/grits. Then clean immediately before any part of the glass dries. You may need to clean part of the glass piece before the grinding is complete to avoid any drying of the powder on the edge of the glass.
Clean well with a minimum of soap and rinse with water that does not have a lot of minerals in it. Polish well with plain paper towels or frequently changed microfiber cloths.
Window cleaning products are not usually appropriate, especially if they contain ammonia.
Avoid introducing oils from the cutter by scoring with a dry cutter or use a specially devised cutting fluid. Cleaning solutions that have additives to be kind to hands or scents should be avoided.
The edges of some glasses devitrify more easily than others. If this continues to be the case after all cleaning efforts have failed, then use a devitrification spray, but continued cleaning is still necessary. There are no short cuts in cleaning.
Saturday, 14 August 2010
Effect of Variations in Size on Bead Annealing
When annealing beads with varying thicknesses, I apply a rule of thumb to be safe.
I take the difference between the thickest and the thinnest part and add that to the thickest part to get the diameter at which I should anneal.
So a bead with a thickest part being 8mm and the thinnest 2mm, gives a difference of 6mm which I add to the 8mm (thickest) part giving 14mm as the diameter to which I anneal.
I take the difference between the thickest and the thinnest part and add that to the thickest part to get the diameter at which I should anneal.
So a bead with a thickest part being 8mm and the thinnest 2mm, gives a difference of 6mm which I add to the 8mm (thickest) part giving 14mm as the diameter to which I anneal.
Tuesday, 10 August 2010
Annealing Beads of different sizes and shapes
It is possible to anneal beads of different sizes and shapes at the same time, if you anneal for the beads which require the most care. It will not matter for the smaller beads or easier shapes if they are annealed longer than the minimum requirement.
Friday, 6 August 2010
Effect of Shape on Bead Annealing
The shape of the bead has significant effects on the annealing time required. This is because the shape has an effect on the speed at which the centre can cool. Spheres have the most even transmission of heat, because the heat can radiate equally in all directions. Cylinders are more restricted in heat radiation because they can radiate heat from the circumference but not so effectively along the length. Flat shapes can radiate heat in only two directions, making them the most difficult to anneal.
As indicated, spheres can be annealed most quickly. The annealing schedules given in this blog apply to spheres as this is the most common form for beads.
Cylinders which by definition are longer than the diameter need to be annealed at two thirds the rate of spheres. So, from the tables you choose the annealing rate for a piece 1.5 times larger than the diameter of your cylinder.
Flat shapes require the most care in annealing so you should choose the rate that is three times the thickness of the piece you are annealing.
These cautions will help to adequately anneal your beads, what ever their shape.
As indicated, spheres can be annealed most quickly. The annealing schedules given in this blog apply to spheres as this is the most common form for beads.
Cylinders which by definition are longer than the diameter need to be annealed at two thirds the rate of spheres. So, from the tables you choose the annealing rate for a piece 1.5 times larger than the diameter of your cylinder.
Flat shapes require the most care in annealing so you should choose the rate that is three times the thickness of the piece you are annealing.
These cautions will help to adequately anneal your beads, what ever their shape.
Monday, 2 August 2010
Bead Annealing Schedules for Spectrum Beads
Bead Annealing Schedules for Spectrum Beads
This table is based on James Kirwin’s work on bead making with variations. This is for cold beads being heated for a secure anneal.
Up to 10mm dia.: afap to 520C, 30 mins; anneal at 300C/hr to 370C; afap to 40C
12mm dia.: 1000C/hr to 520C,30mins; anneal at 210C/hr; 600C/hr to 40C
14mm dia.: 1000C/hr to 520C, 30mins; anneal at 155C/hr; 460C/hr to 40C
16mm dia.: 950C/hr to 520C, 30mins; anneal at 120C/hr; 350C/hr to 40C
18mm dia.: 740C/hr to 520C, 30mins; anneal at 94C/hr; 280C/hr to 40C
20mm dia.: 600C/hr to 520C, 30mins; anneal at 75C/hr; 230C/hr to 40C
22mm dia.: 500C/hr to 520C, 30mins; anneal at 62C/hr; 185C/hr to 40C
24mm dia.: 420C/hr to 520C, 30mins; anneal at 53C/hr; 155C/hr to 40C
30mm dia.: 270C/hr to 520C, 36mins; anneal at 33C/hr; 100C/hr to 40C
38mm dia.: 165C/hr to 520C, 39mins; anneal at 21C/hr; 60C/hr to 40C
50mm dia.: 95C/hr to 520C, 46mins; anneal at 12C/hr; 36C/hr to 40C
Remember this table is for spheres. For cylinders choose the diameter that is 1.5 times the diameter of your cylinder, and for flat shapes choose the diameter that is 3 times the thickness of your piece.
For other information on annealing of beads go here
This table is based on James Kirwin’s work on bead making with variations. This is for cold beads being heated for a secure anneal.
Up to 10mm dia.: afap to 520C, 30 mins; anneal at 300C/hr to 370C; afap to 40C
12mm dia.: 1000C/hr to 520C,30mins; anneal at 210C/hr; 600C/hr to 40C
14mm dia.: 1000C/hr to 520C, 30mins; anneal at 155C/hr; 460C/hr to 40C
16mm dia.: 950C/hr to 520C, 30mins; anneal at 120C/hr; 350C/hr to 40C
18mm dia.: 740C/hr to 520C, 30mins; anneal at 94C/hr; 280C/hr to 40C
20mm dia.: 600C/hr to 520C, 30mins; anneal at 75C/hr; 230C/hr to 40C
22mm dia.: 500C/hr to 520C, 30mins; anneal at 62C/hr; 185C/hr to 40C
24mm dia.: 420C/hr to 520C, 30mins; anneal at 53C/hr; 155C/hr to 40C
30mm dia.: 270C/hr to 520C, 36mins; anneal at 33C/hr; 100C/hr to 40C
38mm dia.: 165C/hr to 520C, 39mins; anneal at 21C/hr; 60C/hr to 40C
50mm dia.: 95C/hr to 520C, 46mins; anneal at 12C/hr; 36C/hr to 40C
Remember this table is for spheres. For cylinders choose the diameter that is 1.5 times the diameter of your cylinder, and for flat shapes choose the diameter that is 3 times the thickness of your piece.
For other information on annealing of beads go here
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