West Ward Estonia
For grinding my 6" mirror, I used a Tile on Plaster Tool . instead of the second 6" glass that I got with my grinding kit.
Using that kind of tool offers several advantages, despite the little effort in making the tool. Since I never ground a mirror on a glass tool myself, I will give a short summary of what people say, who tried both:
• You can save your second blank to make another mirror.
• The channels in the tool minimize the danger of seizing.
• You can grind faster and more efficiently by using less abrasives.
• For big mirrors, the weight of the tool can be reduced.
• Even distribution of the abrasive across the tool.
• No trapped air-bubbles.
• You have to make the tool yourself, which might be bit of an effort the first time.
• Cleaning the tool is more difficult.
• Unbeveled tile edges are a potential danger for scratching the mirror.
• Plaster or cement particles coming off the tool can cause scratches.
Most of the disatvantages can be eliminated by taking precautions, while the advantages are tremendous!
• Dental plaster; or plaster of paris; or any kind of cement preferably without sand and as fine as possible. Dental plaster cures very fast, which makes it the best choice.
• Slow (2-4 hours applying time) curing epoxy glue. I made good experiences with white Porcelain epoxy. Of course it should be waterproof.
• Porcelain tiles cut in small squares (~2,5 cm) . Porcelain is best, because it is very hard. If you can only find big tiles, then cut them yourself with a tile cutter.
• Masking tape and aluminium foil.
• Carbo grinding stone. The kind that you use to sharpen carpentry tools. (Buy a cheap one!)
First you cover the mirror face with thin plastic kitchen foil and create a mould by wrapping aluminium foil and masking tape around the blank. The s