8x10 etched glass found in darkroom - ID?

[syncrasy]

I found a couple of loose pieces of glass in my late father's darkroom. One is 8x10 glass, the other is 9.25x9.25" plexiglass. Both appear to be etched/frosted on one side. The plexiglass is more opaque than the glass piece. The attached photo shows the plexiglass on the left, glass on the right.

Because of the large sizes, I assume he could not have used these with his enlargers (Beseler 45 and 23), so I'm puzzled as to their identities/uses. (I'm cleaning out the house prior to an estate sale so I'd like to know if these pieces are truly specialized and have more value than just plain ol' glass.)

Are these diffusion or Anti-Newton ring glass pieces for a different type of enlarger or purpose? Or something else entirely?

Thanks for any help.

 

[Neal]

If no one else is going to guess, I will take a stab at it. They might be ersatz anti newton ring cover sheets used for proofing rolls of film.

Neal Wydra

 

[syncrasy]

As good a guess as any. Thanks.

The 8x10 glass piece is rather thick (3/16 inch or about 4.76 mm) with smooth flat sides and slightly bevelled edges (very well-cut glass). I notice that Focal Point still sells ANR enlarger glass in 1, 2, and 3mm thicknesses, so I wonder... Is my glass too thick to fit alongside an 8x10 negative carrier for an enlarger?

 

[DREW WILEY]

It would probably have been used as a diffuser between the light source or mixing box and the neg carrier. Plastic like this is not very good as a replacement for actual ANR glass because it can bend (bow) toward heat and not remain flat. It is also slowly affected by humidity in this respect. But some people have successfully used it right atop negs in conjunction with cold lights, which obviously operate relatively cool. Whether it fits in your own carrier all depends. Carriers aren't all the same.
But real Focal Point glass would be a better alternative, regardless. There is one application where I use both - the frosted
Plexi above the Focal Point AN glass to act as a secondary diffuser (a white Plexi diffuser is about an inch above that one).
In this case, the lower plastic diffuser has been ground down with the perimeter thinner than the center, to accommodate for
the illumination falloff of a particular enlarging lens.

 

[syncrasy]

Thanks for the description, Drew. I'm surprised to hear that you used both AN glass and plexiglass in the same application. Very interesting.

Today I found another piece of AN glass in his darkroom. This one is bigger and an oddball size -- about 10x16 inches -- so who knows what he did with that one.