My Uncle has made a number using a custom stained glass shop sandblaster and they turn out well. Has made them for cameras to 12x20. After talking with the shop owner he was advised to wait til they were just ready to change to new sand as the used sand was a bit finer than the new stuff and would work better. He tried the old sand and then the new sand and in use he and a few LF friends agreed the glass blasted with the older, used sand worked better.
Cost was very low as the owner could put in a dozen sheets of 8x10 at a time.
I think that would be a good size for aluminum oxide.
For a given grit size, SiC will work faster than Alox, but Alox will provide a smoother finish If you're trying to get a very satiny, "just this side of polished" finished, I'd use Alox. Kind of like what Willie says above about used sand in a sandblaster.
But that's from an optical shop viewpoint...they grind to hit a certain radius of curvature and then to minimize polishing time. Slightly different requirement.
Newly made large format dry plates available! Look:
https://www.pictoriographica.com
I have used 800 grit sic with good results
Science is what we understand well enough to explain to a computer. Art is everything else we do.
--A=B by Petkovšek et. al.
Terrific video, Dieter!
Regarding the ground glass, I recommend that people use a sanding block along the edges to get rid of any sharp areas. In addition, I prefer a larger piece of glass, say 2"x2" for the grinding piece.
“You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.”
― Alexander Den Heijer, Nothing You Don't Already Know
Good thread
I missed
During my relocation
far from the madnining crowd
Tin Can
I have a large (appx. 16x20") sheet of heavy plate glass stashed away in the bowels of my basement - which I'd used as the "grinding plate" for a number of ground glass pieces. Most of these pieces (for various formats) I'd ground with a supply of 500 grit carborundum given to me by non other than Will Whitaker, back in the day when he lived near me and we used to hang out.
The thing about that big piece of plate glass - is that over time it eventually acquired (from all of that grinding) a bit of a concave surface...very subtle indeed but enough so that when placed (ground side up) on a level surface...a large ball bearing placed atop it would roll towards its center point! .
Good tip, Jim!
“You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.”
― Alexander Den Heijer, Nothing You Don't Already Know
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