Thanks everyone!
John, I first started sculpting on glass using the Aves two-part Apoxie Sculpt putty. The drawing was taped under the glass. The glass does need a release agent, otherwise putty the really sticks to the glass after it cures. I tried a variety of sprays, cooking oils, and vaseline. All worked to a point, but it's a bit of a crap-shoot - too little and the putty sticks anyway. Too much and the putty doesn't stick to anything - including itself. I then tried waxed paper. Less messy, but the water used to smooth and blend the putty and keep it from sticking to the tools eventually broke up the paper. The one time glass and sticking wasn't an issue was when I used Sculpy III to make Cheech Wizard (see the old site if you can access it, I can't). Once completed, the piece was baked in the oven, cooled, and easily sliced off the glass. No release agent was needed.
I finally resorted to using the sheet plastic; .030 at first and, while it worked, it was a bit too thick and was a chore to cut out. I went to .010 for the Harlequin, but that was to thin; it curled under the curing putty. The next one will .020. In all cases of using the plastic base, the figure was drawn on first, the piece cut out, and the drawing cleaned up as needed. I use a fine line water proof marker for the final drawing, so water and my handling doesn't erase the lines.
All of my scratch-built flats are averaging around 1.5mm thick or so. There are slightly thinner areas and slightly thicker areas. Overall, they are marginally thicker than commercial metal flats.
Nick, you make a valid point. One of the issues of sculpting over the glass was being unable to see through the putty. Once a flat sheet was rolled out, You had to feel your way around the drawing's perimeter to get the outline. I uses a series of guidelines - a grid and angles - to show me the top of the head, the bottom, shoulder lines, etc. Once the outline was set, I cleaned up the edges (including adding more putty if necessary), flat sanded the face to get rid of any undulations, then transferred the drawing to the flat sheet of putty.
PJ, not smoking anything, but I do tend to get a lot of gas and oil fumes when working on the MGs. I also tend to indulge in the results of my wife's beer making hobby. She's made a clone of Theakston's Old Peculier that'll knock your socks off.
Cheers,
Glen
