Bubbles Between Layers - Design

Design your work to minimise the possibilities of trapped air.

One way to do this is to use strips. Lay thin strips of glass on edge and fuse these together, instead of layers stacked on each other.

Another is to design work with many smaller pieces, rather than large ones. These create more pathways for air to escape.

Some advocate cutting the bottom layer in several strips to allow the air exit spaces from between the glass layers.

Note that all these methods leave marks of where the edges of the cut glass was, so they need to be planned to fit with the design.

In general terms, you need to think about how the air will move out of the piece. Are there places where there is no escape for the air? Allow a channel for the air to move from the centre to the outside.

Glass arrangement considerations
Supports
Using baffles

Bubbles Between Layers - Arrangement

There are a variety of ways to minimise bubbles between layers.

You will have noted that there are smoother and rougher sides to the glass. Putting the two rough sides together will increase the number of small bubbles in the finished piece. But the opposite –smooth to smooth – does not produce the smallest bubbles. The fewest small bubbles are produced when one smooth side is touching the rough side of the other layer of glass. This “roughness” allows any air to find a way out. Smooth to smooth tends to produce fewer but much larger bubbles.

Design factors
Supports during the forming stage
Using baffles

Attaching a Spider to a Lamp

To get the maximum support from the spider, bend the legs to fit the shape of the lamp. Then clean the spider assembly well with steel wool, or if particularly dirty with fine sandpaper, until it is bright again.

Apply flux and run a film of solder onto the legs where they will be in contact with the lamp. This will give you an indication of the amount of heat required to solder the legs to the lamp. It will also make it easier to fix the legs to the lamp once the appropriate temperature has been achieved in the legs.

You need to use the full power of your soldering iron, as the brass soaks up a lot of heat. If your iron is small you may need to change to one with higher wattage for this work.

As the heat is transferred quickly to all parts of the spider, wear gloves or hold with pliers while soldering.

Hanging Panels from the Borders

The hanging method for copper foiled and leaded panels depends to a large extent on size and weight. The larger and heavier the panel is, the stronger support that is required. Smaller light weight panels are not usually a problem as the solder lines and joints can take the weight. Leaded panels require more support than copper foiled panels once they are over a few kilos, or are anything but rectangular.

For heavier panels you need to have stronger supports than just the perimeter calmes or solder beading.

For rectangular panels you can use a stronger edge came such as zinc or brass. Solder this to each meeting joint throughout the length of the panel. This distributes the hanging stress across the panel more effectively. Simple soldering at the four corners of the calme will rely on just those solder joints to carry the whole weight of the panel.

You need to make the vertical borders of single pieces so that you are not relying on the strength of a single solder joint at some point along the side. Although the joint may be strong enough at present, it must stand up to the weight of the panel over a long period of time.

All this relies on secure attachment of the hanging hooks or wire

Glass Weaving

In its essence, weaving is creating a series of strips with waves, moving alternate ones a half step along and inserting straight strips into the channels provided.

It can be as sophisticated as you can devise, but remains the shaping of a series of strips through which other, straight strips are threaded at right angles to the shaped ones. As in cloth weaving, there are a great many variations that can be devised.

You can use a variety of material to slump over – covered steel pipe, cut up kiln shelves, brick, fibre board, etc. - but you must remember that you will need at least 10mm height, as the upper and lower pieces of glass are 3mm each and the one inserted will also be 3mm, leaving only 1mm tolerance. You also need to ensure the material slumped over is far enough apart to accept the width of glass you will be threading through. If you are using 20mm strips, you probably will need at least 25mm intervals between the slumping strips. Make sure they are parallel as well as evenly spaced. You will need to soak at slumping temperature longer than for a simple shape, as you want the slump to be close to vertical.

When threaded, you can tack or full fuse the piece and subsequently slump it if desired. The amount of space between the “threads” will depend on the steepness of the slump. If the slump is too deep you will find the lines of the “threads” will be uneven and may even fold over one another.

So this is yet another area of kiln forming that is simple in principle, but requires a lot of experience to get a really good looking piece at the end.

Drilling Glass, 2

Using a Drill Press

It is best to have a drill press if you are doing a lot of drilling. It provides a stable drilling action and the pressure on the bit can be controlled.  It is important to ensure the bit is running true without wobble. The drill press should have instructions to help correct any untrue running of the chuck.  Make sure the drill bit is secured firmly.  Core drill bits are easier to keep true, as they normally have a threaded fixing.

With a drill press, you can drill continually until the hole is completed, or until a white paste or dust begins to appear. This indicates the drilling is being done dry and will in a few moments heat up the glass too much. When the white paste appears, back out of the bottom of the hole a little to allow water to flush the glass out. Then continue.

Keep a firm grip on the glass being drilled. Maintain its position, especially if you are intending to back off intermittently to allow water to the bottom of the hole. This enables you to get back into the hole without scratches.

If possible, submerge the piece. But if that isn’t possible, just squeeze a little puddle of water on the surface and watch it swirl around. You can see if it is pulling ground glass out of the hole by watching the circulation. Placing a plasticine or clay dam around the drill area will keep the water confined.

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. Always remove each core right after drilling. They are very difficult to remove if there is more than one in there.

Every diameter drill bit has an optimum drill speed. The smaller they are the faster the speed required. Based on what the manufacturers recommend, a Dremel running at top speed is way too fast. When using a Dremel for drilling glass, slow it down with the speed control. Drill presses do tend to be on the slow side for glass drilling so it takes a bit longer, but there are big advantages in other respects.

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

Keeping Wire Hangers in Place

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.

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.

• Drill with the glass under the surface of the 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 / 2 inches in diameter and press it around the drill site. Fill the ring with water to cool the drill site and glass. Diamond coolant is not necessary, but can extend 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 many holes or large ones.

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, 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

Drilling Glass, 4

Avoiding Chipping

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