A really good, bright GG from back in the day was a combination of being blasted for the matt surface, then being fumed with hydrofluric acid (thanks DJ!!!) to create a little transparency, so there was some aerial image going through it... But enough matt surface to focus on... Those fumed glasses were mostly made with banned substances, with the last being made in Belgium (thanks, Drew!!!) some years ago... And were a specialized process, difficult to make proportions right for a good balance, and may have a different effect with long or short FL's... (Almost like a semi-fresnel effect...) You will often find them on Graflex SLRs or other reflex cameras as the viewing screen...
If you need a good, quick emergency GG, I had to use some window frosting spray to paint over some windows, and it had a nice ground surface (but not as tough as the glass) but if it is inside the camera, and you go easy on it, it should last for a while... (Mist over it a few times making very light passes, with dry time in between...)
Some frosted/textured surface acrylics have a surface that reminds me of the old style etched/blasted glass GG's, so I might try them out sometime...
Steve K
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