Removing silicone

To remove silicone before it is cured you use a putty or other straight bladed knife to remove any of the uncured paste. Then wipe the area clean with isopropyl alcohol to remove any leftover residue.


After it is cured you should first you should remove as much of the silicone as you can with either a knife or a razor.

A solvent can them be used to remove any oily residue or any remaining silicone. It may be necessary to soak the silicone in a solvent overnight to break it down.

A list of solvents in the order of aggressiveness in attacking the silicone:
Paint thinner (mineral spirits)
Toluene
Xylene
Acetone
Methylene chloride.

When using solvents, as with any material, proper safety precautions should be observed. Material Safety Data sheets are available upon request from manufacturers. Similar information for solvents and other chemicals can be obtained from manufacturers.

There also are “Silicone Eaters” on the market now. The chemical composition is unknown, but are less messy and more expensive than some of the other solvents. Use according to instructions.

Glass Polishing Machines - Linisher

A wet belt sander, or linisher, is a machine intended to grind the edges of flat pieces of glass. It can do some work on bent, shaped, or slumped work, but its primary function is edging work while it is flat.

Table top model

The machines consist of a vertical or near vertical belt and a water supply to keep the belt and work lubricated and cool. Work generally starts with a low numbered grit belt, perhaps 80 grit, and then proceeds through the higher numbers. For example: 80, 120, 220, 400, 600, cork. Each stage should approximately half the grit of the previous one.

Floor standing model

Even with a cork belt, don’t expect a gloss you would see from a fire-polished piece. For that you need a cerium oxide belt or a felt belt with cerium oxide paste. Trizact is a brand name for fine polishing belts not requiring cerium oxide paste. These may be substituted for the more messy paste methods.

You can buy silicon carbide or diamond belts for a wet belt sander. The diamond belts are very expensive, but much longer lasting with proper care. If your belts are likely to receive rough treatment stick with the cheaper silicon carbide belts.

Cooling Events

This is based on Graham Stone’s work with float glass. The temperatures are applicable to float glass, and so need to be adjusted for a particular glass, but illustrate the principle of how heating temperatures affect the glass. Temperatures in degrees Celsius.


600 Common temperature for crash cooling toward. Glass beginning to "freeze".

555 Annealing temperature of float. Bungs in.

515 Approximate Strain Point of float.

535-400 Critical slow cooling down phase for float that overlaps annealing range.

400-300 Medium cooling down ramp rate.

300-10 Fast cooling down ramp rate. Cracking the kiln open possible.



Based on Firing Schedules for Glass; the Kiln Compainion, by Graham Stone, Melbourne, 2000, ISBN 0-646-39733-8, p24

Casting Temperature Events

This is based on Graham Stone’s work.
Temperatures are in degrees Celsius.

660 Bungs still out for casting.

710 Mould "curing" starts (molecular moisture being expelled).

820 Bas relief complete. Whiting gives off CO2

850 Glass flowing. Viscosity decreasing quickly. Common casting temperature

870 Fine mould/mold detail complete

900 Plaster moulds becoming very brittle

950 Un-reinforced plaster moulds no longer viable.

1100 Glass runny enough for sand casting and other manipulative techniques.


Based on Firing Schedules for Glass; the Kiln Companion, by Graham Stone, Melbourne, 2000, ISBN 0-646-39733-8, p24

Disposal of Used Bullseye Thinfire

The main ingredients of Bullseye’s Thinfire are cellulose, aluminum hydroxide, fiber glass, and organic binders. It is predominately a nuisance dust and irritant.

Use a vacuum sweeper with a high efficiency filter and a bag rated for plaster dust. Also many vacuums with a HEPA filter system will be sufficient. Wrap the disposable bag in another -preferably paper - bag to avoid dispersing the dust when it goes into the rubbish.

Viscosity Changes with Temperature

This is based on Graham Stone’s work with float glass. The temperatures are applicable to float glass, but illustrate the principle of how viscosity changes in a non linear pattern with the increase in temperature. Temperatures are in degrees Celsius.

515 Viscosity 10145 poises (approximate strain point of float)
555 Viscosity 1013 poises
610 Viscosity 1010 poises
730 Viscosity 976 poises
850 Viscosity decreasing faster
900 Viscosity now 105 poises and falling

Based on Firing Schedules for Glass; the Kiln Companion, by Graham Stone, Melbourne, 2000, ISBN 0-646-39733-8, p24.

This shows that viscosity changes rapidly from the lower strain point (the solidification of glass) to annealing.  The change slows from the annealing point to full fusing, but changes rapidly after that.  This is an important factor to control in casting and free drops.

What is viscosity
Graph of the changes

Paint – Temperature Effects

This is based on Graham Stone’s work with float glass. The temperatures are applicable to float glass, and so need to be adjusted for other glasses, usually a bit lower. But these temperatures illustrate the principle of how heating temperatures affect the paints. The temperatures will need to be adjusted when fired on other glasses than float. Temperatures are given in degrees Celsius.

570 Low firing glass enamels fired
650 Silver stain fired.
690 Low fire red enamel burnout.
730 "Paradise" paints fired.
750 Onglazes fired.
800 Lustre burnout begins.

Based on Firing Schedules for Glass; the Kiln Companion, by Graham Stone, Melbourne, 2000, ISBN 0-646-39733-8, p24

Iridised Side of Glass

It can be challenging to determine the iridised side of glass. The coating is very thin and so cannot be seen by looking at the edge. There are several ways of testing for the coated side. Two that I find useful are:

The pencil test – In this you put a pencil point or other point to the glass. You then look for the reflection at an acute angle to the glass. If there is a gap between the point and the apparent surface of the glass, the coating is on the other side. And in reverse, if the point is immediately reflected with no gap, the point is touching the coated side.

Another test is the fingernail test. If you have sensitive nails, you can feel the difference in surfaces by gently dragging your nails at an almost right angle to the glass. The rougher side is the coated one.

There are other tests but these two work for me.

Foil Lifting While Soldering

There are several possible reasons for this.

The main one is that the soldering is too slow. This causes the adhesive on the foil to fail before the solder has a chance to become rigid.

The foil may not have stuck to the glass firmly. Reasons for this are many, but some are:

- Dirty glass. Make sure the glass is washed and polished clean, especially if you have been grinding, when you need to get all the glass dust out of the pits on the edges.
- Oils from your hands. The oils can be natural or from hand creams. If you have oily skin or need to use hand creams consider cotton gloves for use when handling the glass prior to and during foiling.
- Inadequate contact between the foil and the glass. This can be from both the above, but can also be that the foil was not pressed firmly to all the sides and edges of the glass pieces.


The foil adhesive may be inadequate through manufacture or age. If a test piece does not feel tacky to your finger tips, it is not going to stick to the glass very well.

Grinding for Copper Foil

It is often thought that every piece of glass has to be ground to enable the foil to stick well to it. There are conflicting views about this. I am firmly on the side of not grinding. The impact adhesive on the back of the foil is thin and will not fill the depressions caused by grinding. It will adhere to a smooth surface more strongly than a rough one. Remember the purpose of the foil is to provide a surface to carry the solder. It keeps the foil in place until the solder bead is completed on both sides. It is not a permanent adhesive. So some of the discussion about which surface is best is academic.

There are ways of obtaining clean cuts that help avoid the need to grind.

Score with an even pressure. This helps the glass break clean with few shells or chips. If there are any overhangs, you can eliminate them with a quick wipe of the edge of the cut piece on the waste piece.

Ensure you hold your cutter vertically. This will encourage the break to be at right angles to the surface giving a clean smooth cut face.


The only NEED for grinding is to adjust an inaccurate cut. We all make inaccurate cuts from time to time.