As a follow up on the tde discussion, on my 5" silicon mirror that I've finished grinding that does NOT have a tde, when I do the tic tac toe test, when the mirror is on top the center wears first, when the tool is on top the edge wears first irregardless of any other factors.
Anyway, as I said, it was fairly easy to whip out a silicon mirror using the machinery at the optical shop. 15min w 80grit gave me more sag than I needed for my desired f/10 5 more w tool on top, then same with220 grit, then the same with 240 alum oxide ( the killer grit!!)20 min with 20u ao(10' top, 10' bottom), and the same with 9u, and its done.(Less than 2hrs including measuring and testing)
I then took the convex tool, cut a 5" disc out of a silicon polishing pad (Rodel Suba550), cut this into thin pie shaped sections(to compensate for the curvature, and applied them to the tool. In 15 min 80% polished out,(Mirror on top) center first working towards edge. Flipped, 15 more min, 95% done still lite pitting on extreme edge. Was going to test friday nite(knife-edge), but... lost power. And again sat nite...The perils of west Marin. We'll try after work tomorrow. Depending on how it looks, soon decisions on how to proceed will be mandated.
Trying pads to get test?? Hard with flat work, typically to much roll off to achieve good test clear to edge, I assume same applies to spherical work.
Tropical Pitch with aggressive collodial silicas(pH 9) as suggested by Bratislav
We'll see................
Bill Marriott Forest Knolls, Ca btk@ix.netcom.com