Identifying Durst AR Glass

[Drew Wiley]

It's hard to say how they made it; but it's a soft slightly-greenish glass that is pretty fragile. I use very gentle woven scrubbers for it, just like you'd use for a valued teflon fry pan. Once they needed thicker glass for setting registration pins, it was in a whole different league. Warren Condit told me he got his thick AN glass from Belgium, back when he was alive, and I had him make me up some special registration stuff with that. The glass was so good that I wanted more, but it was no longer being made. That is some ornery glass to machine! AR glass is also hard to work with, since the current coating tend to be very hard. When in doubt, always try to obtain a scrap to test first.

[Tin Can]

I can tell by just touching my AN glass that cutting it would be a mistake. One is scratched, but I have no need for smaller than 8X10.

I treat my glass very carefully, stored on microfiber, cleaned only as needed like fine crystal.

[Nathan Potter]

Typically if glass has a slight greenish tint (especially when viewed on edge) it is a type of soda lime based glass
likely to cut easily. Soda lime type was not the best to use in an enlarger for color printing due to the slight color shift imparted to a print. borosilicate based glass is a low expansion type which is clear when viewed on edge and called Pyrex (when from Corning) or Schott (called BK7), for example, both a crown glass of low index of refraction. Borosilicate is more difficult to cut so a diamond saw is recommended rather than simple scribing. Borosilicate type would typically be used for AR coating purposes with the AR coating being magnesium fluoride or silicon dioxide in thin (few hundred nanometer [nm] thickness) by vacuum deposition. The AN glass can be found in both soda lime and borosilicate types and is actually an etched surface of variable roughness on the order of 50 to maybe 250 nm. thickness as measured using interferometric techniques. The performance of AN glass varies considerably as a function of the depth of the etched surface and how it was formed.

Nate Potter, Austin TX.

[Tin Can]

Tried to buy Bon Ami today for cleaning glass, the big store never heard of it. Amazon...

[Drew Wiley]

Nathan - Current AR picture glass is often clear titanium coated rather than magnesium fl. But high-quality AN glass was never chemically etched. If you look at true Durst AN glass there is a distinct regular ripple pattern to it, not something random. It is not borosilicate by any means, and could well be soda-lime, but plano-parallel optical glass. The slight color bias amounts to less than 2 cc of cyan for the 2mm thickness, so is almost negligible. Very few glass types are clearer, like acrylic can be. Interestingly, my samples of thick Belgian AN glass shares the same ripple pattern.

[Jac@stafford.net]

Tried to buy Bon Ami today for cleaning glass, the big store never heard of it. Amazon...

You might want to try Stoner's Invisible Glass. It is the best glass cleaner and clarifier I have ever used.
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[Tin Can]

You might want to try Stoner's Invisible Glass. It is the best glass cleaner and clarifier I have ever used.
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I also want to clean glass dry negative plates before subbing. It sounds good for GG and AN.

any thoughts?

[Jac@stafford.net]

I also want to clean glass dry negative plates before subbing. It sounds good for GG and AN.

any thoughts?

Randy, I have not tried it on glass negatives. I never comment upon that which I have not used. Perhaps tomorrow morning I will try it on some old, insignificant glass plates. It did work well on a filthy piece of glass I use on my Focomat IIa and new glass, including one AN for the 8x10 Saltzman. No after deposit.

I can tell you that it resurrected two windshields that nothing else could help, but they are not photo image things.
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