Re: ATM wedge removal/dental stone

[Aplanatic@aol.com]

Hi Hal:

>Since this is my first attempt at making a 
>tool, I assume that being my
>mirror has a diamond generated curve 
>that I pour the stone mix onto the
> blank so that the mix conforms to 
>the curve of the mirror and also that a
>1-1/2-2" dam be built up around the 
>edge of the blank  to contain the mix.

Yes, exactly.  After making a dozen or so tools, here's how I do it.  I place aluminum foil on the front of the blank and wrap the foil around the back side of the blank to hold it in place.  

To make the dam I take a long piece of foil (12" wide) and fold it lengthwise twice so that it's about 3" wide.  Taking the edge of my hand, I rub the foil so that it starts to curl inward on its own.  I then wrap this foil dam around the mirror by taping the first end to the wrapped blank, pulling the foil tight, and then fastening the free end with tape.  I make the dam about 2" high and pour the stone as close to the top of the dam as possible.  Simple.

>Also the blank is ( plate )glass 12.5" 
>and 7/8" thick, so is
> there danger of  damage to the blank 
>due to the heat from the mix ?

I've made tools from plate blanks and have had no trouble at all.  Just remove the tool after it's hard enough to be safe to handle (about 15 to 20 minutes) but before it gets hot.  It continues to heat for about 30 minutes after initial set up.  It's thermal shock that breaks plate glass, not slow heating and cooling.

Dave Rowe