Here are some pictures to show you the general idea. I do not use epoxy when I make tile grinding tools. Start by lubricating your mirror with just about any slippery lubricant (lard, olive oil, butter, etc.) and wrapping it with saran wrap (clingfilm in the UK). Garbage bags and drycleaner bags also work well. Large mirrors should be covered with two layers of oil and saran wrap. The tiles will contact the wrap, so take care that there is no exposed lubricant.
Then build a dam around the mirror blank and set the tile mat inside it. It would not hurt to degrease the tile mat by washing in dish detergent, then rinsing. Grease on the tile may impair adhesion to the dental stone. Center the mat with about 1/4" margin between the tile and the dam. Mylar drafting film is a dam good dam material. Some use plastic slats from vertical blinds. Even aluminum foil or waxed cardboard will work if nothing better is available. Secure the dam with masking tape or whatever will hold it tightly to the rim of the mirror blank.
Mix the dental stone (Modern Materials Buff Labstone) with water and scoop it into the mold. Do NOT use plaster! Dental stone is commonly available if you look in your yellow pages under "Dentist: Equipment and Supplies". In a strange foreign city (Vancouver) it took me five minutes to locate a supplier. Properly mixed dental stone will not pour; if it does pour, you have too much water, so add more powder.
If poured dental stone flows, it has too much water. |
Dental stone liquifies with vibration. It flows flat and bubbles come up. |
 Stoning the channels with a whetstone |
To get the goop to settle between the tiles, acquire a flat back, and get rid of most bubbles, vibrate and rattle the entire mold. The goop will liquify, the back will flow flat, and bubbles will rise. Take care that the tiles to not rise; you can check them with toothpicks. The toothpick holes close up immediately when the goop is vibrated.
After the dental stone is hard, you can clean up the channels with a whetstone. If there are any cavities in the channels, they can be filled in with a thin slurry of dental stone, smeared by hand into the cavities and over the face of the tile tool. A second cleanup with the whetstone may be required; you can save some time if the grout is not completeley hardened. If the tile has sharp edges, the whetstone will bevel them.
The result is a beautiful, durable grinding tool that matches the curvature of your mirror blank. Now is the time to be glad that you did not use hex tiles, plaster of paris, epoxy, or other obsolete materials.
After grinding has achieved good contact between the glass and tile, you should make your pitch lap foundation. The process is the same, just leave out the tiles. The complete paper tells you how to finish your lap foundation and prepare it for application of the pitch. DO NOT WAIT UNTIL FINE GRINDING IS DONE TO MAKE YOUR LAP FOUNDATION!
Finished tile grinding tool conforms to pre-generated curve of your blank |
I do not claim that my way is the only way. As impossible as it may seem, others may also have a few good ideas. To see them, go to...
Kuper Controls Article on making tile tools; too bad they use hex tiles!
Got Grit Article on making tile tools; but his aren't beautiful like mine! I guess they work.