An update on progress with my 33" by 1 1/2" thick plate glass mirror.
There has been a bit of a set back.
After 20 hours of polishing (by hand) I was not altogether happy due to the fact that a significant number of smallish pits remain in evidence on the outer 1" of the radius.
Even though they were invisible to my naked eye, they were clearly visible using a 10X eye loupe in conjunction with a LED light source shone (at night), at an angle across the optics surface.
I had noted the existence of these artifacts (from the grind), at the 12 hour point in polishing, expecting to see their disappearance before the 20 hour polish time. However the difference in their appearance over the eight hours between the two inspections was IMHO not significant enough, so decided to go back to a regrind.
In fact right back to #220. Since have reworked #400 and #800 (over considerably longer periods than previously). Now ready to restart the "polish".
Concurrently have been working a 25" f4.4 (1 1/2" plate). Well through the polish with this one, using the same 17" pitch lap as used for the 33, but heat pressed to conform to the tighter curvature of the 25. When this is fully polished out will again use this same lap for the 33.
A 33" mirror is a sizable piece of glass. Started out at around 115lbs. After curve was generated (by hand), weight was down to around 95lbs. Anyway took a picture of it, (after the first polish before going back to the grind-looked so nice to the naked eye), sitting on the "hand truck" I use to move it about.
Stephen.