Identifying Durst AR Glass

[neil poulsen]

So, I'm in a bit of a quandary. Years ago, I purchased two sheets of 10"x10" glass from the Durst graveyard in Hillsboro, Oregon. One was supposed to be regular Durst glass, and the second was marked "AR". But in comparing the two sheets of glass, reflections on all four sides look identical. However, comparing ANR Omega 4x5 glass with regular Omega 4x5 glass, reflections on one side of the ANR glass are blurry. (I'm comparing reflections of a ceiling light.)

As to my question, is it as easy to distinguish Durst AR from Durst non-AR glass as it is to distinguish Omega ANR Omega glass from Omega non-ANR glass? I'm wondering if, contrary to the labeling, I was sold two sheets of regular (non-AR) Durst glass.

I say "graveyard" above, because (I was told) this particular company had purchased all the parts, design rights, and remaining 8x10 enlargers from Durst, when Durst went out of business. It was quite something to see all of these huge 8x10 enlargers, accessories, and related equipment in one large warehouse.

[vinny]

All the AN glass i have is pretty obvious.

[ic-racer]

I have original Omega and Durst AN glass and I also have replacement glass from FPoint. In all cases, the image you see when you look through it is blurry. It is pretty obvious.
The Durst glass indicates "AN" on the package, not "AR."
I did not know Durst offered AR glass but it would be difficult to tell that from regular glass. AR glass is coated rather than pitted. I have never used AR glass, maybe you could let us know if it is any better or worse than AN. Jens has ideas on the topic: http://www.durst-pro-usa.com/glass.php

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[Drew Wiley]

All true anti-newton glass will have a soft reflection on the AN side. Authentic Durst as well as Omega AN glass is an especially high quality type that has a barely perceptible wave-like pattern to it, versus just overall tiny dimpling as in generic AN glass. Both these brands of glass have a very slight green to them, just like thin float glass. They are not optically coated, though they are flatter and more optically precise than ordinary float glass. I have never had any luck substituting coated AR glass for true AN (and I have tried a lot of em!). With large format negs, I find that the generic AN glass from Focal Point works perfectly well. But when push comes to shove, like when printing little med format negs using high MFT enlarging lenses, the brand name Durst glass is less likely to reveal the AN pattern in textureless areas of a high contrast print.

[Drew Wiley]

Ooop... Freudian slip. I mean't MTF lenses, obviously. "MFT" is the designation of an equipment table I sell here during the day.

[neil poulsen]

I have original Omega and Durst AN glass and I also have replacement glass from FPoint. In all cases, the image you see when you look through it is blurry. It is pretty obvious.
The Durst glass indicates "AN" on the package, not "AR."
I did not know Durst offered AR glass but it would be difficult to tell that from regular glass. AR glass is coated rather than pitted. I have never used AR glass, maybe you could let us know if it is any better or worse than AN. Jens has ideas on the topic: http://www.durst-pro-usa.com/glass.php
124955

Actually, the "AR" was hand written. But the "Durst" was printed in color.

[neil poulsen]

I'll look again, taking into consideration responses written here. Hopefully, what I have is the real thing. Thanks

[Ginette]

I'll look again, taking into consideration responses written here. Hopefully, what I have is the real thing. Thanks

The AR is different of the AN. See this Durst Pro lesson #13 about glass http://www.durst-pro-usa.com/resources.php?tab=13#TabbedPanels1

[Tin Can]

The AR is different of the AN. See this Durst Pro lesson #13 about glass http://www.durst-pro-usa.com/resources.php?tab=13#TabbedPanels1

All good advice. Thanks for sharing.

[Drew Wiley]

Durst never made an AR glass. That was coated Schott glass hypothetically being marketed by an individual. I don't know if any was actually delivered.

[neil poulsen]

Interesting. I've had a chance to do a pretty thorough comparison of the two 10x10 sheets of glass that I have, and I have a follow-up question.

The two sheets of glass are in fact from the Durst U.S.A. located company. Actually, I purchased them from a former partner of that company several years ago. Both sheets of glass are labeled "Durst", etc. One sheet has "AR" hand-written on it. I was told that both sheets are really excellent, precision glass produced by a company in CA.

The only difference between the two sheets of glass that I can detect, is that reflections of trees against an overcast sky outside of our window on the AR labeled glass are definitely not as bright (darker) as the same reflections from the non-AR labeled glass. To eliminate position as a possible reason for this difference, I traded positions of the two sheets of glass, and still, the AR labeled glass is not as bright.

Turning over the AR-labeled glass, I could still see that reflections on the non-AR labeled glass were brighter than those of the AR labeled glass. So, same effect on both sides. Also, I could see no hint of color, green, magenta, etc., at all on the AR labeled glass.

QUESTION: What will be the effectiveness of reducing unwanted artifacts (e.g. Newton rings) when these two sheets of glass sandwich an 8x10 negative?

[Drew Wiley]

True Durst glass always came from Europe, not CA. Perhaps the "Durst" aftermarket sales agency in Oregon was having AR glass cut here at OCLI, back when they were the key player in optical coatings. That torch has since passed on to Focal Point. Since you live in a relatively high humidity area just like I do, I doubt that AR glass will help much with Newton rings. You need true AN glass. I once had samples of AN glass from all over the world. Not many choices nowadays. The Focal Point version is dimpled and generally fine for large sheet film and flatbed scanners. They can provide various thicknesses and cut and finish to size at a reasonable price. True Durst AN had a very subtle ripple pattern to it, and was quite expensive. There was once a similar Belgian glass, perhaps from the same source. I routinely use AN glass for BOTH top and bottom glass with slick films, including all color films. Contrary to routine gossip, this does not at all affect sharpness, nor will any pattern be apparent in the print IF it is the right kind of glass for the degree of magnification and incidence of light. When push comes to shove, true Durst glass is superior in this respect. But I wouldn't worry about it unless you're significantly enlarging MF negs with very high MTF Apo enlarging lenses. Reproduction of dye clouds in color work is almost never an issue. But it does help to have everything in your enlarging system very precisely aligned, then keep your depth of field shallow, focused only on the emulsion itself, preferably with a longer-than-"normal" focal length lens. If you still can't cure Newton rings, you can buy Anti-Newton spray from scanner supply companies. It has to be cleaned off afterwards, however.

[Tin Can]

Hmm.

I guess I better keep my supply of, whatever I have, AN glass, which is easily differentiated from any plain glass. All 8x10 exactly with finished edges. I use them on my scanner. Got them with mystery 8x10 negative carriers, which nobody can identify.

[ic-racer]

Since this thread stared I obtained a Philips additive enlarger. The negative carrier is capable of holding glass and I used some of my damaged Durst AN glass to make the appropriate sized pieces. I like the way the glass is held in place, this is like a baby version of my 10x10" Durst carrier.

http://img.photobucket.com/albums/v670/ic-racer/2015/DSCF7255.jpg
http://img.photobucket.com/albums/v670/ic-racer/2015/DSCF7257.jpg

[Drew Wiley]

Cutting some of these specialty glasses can be a bit tricky, depending. I alway use a cutter wheel designed for tempered glass, which has a bit different angle than
the ordinary kind used for float glass. But I've got one of those big pro machines which accepts different wheels. Some AN is soft and easy to cut, some is relatively hard, and virtually all modern AR coated glasses are hard and can be ruined trying to cut them with conventional gear. When in doubt, have a trusted local glass shop do it. And always score the smooth side of the glass, not the textured AN side.

[Jim C.]

Drew, just curious is that glass cutter machine similar to a wet tile saw ?
Been musing about hacking a wet tile saw to be able to cut glass.

[Jac@stafford.net]

Drew, just curious is that glass cutter machine similar to a wet tile saw ?
Been musing about hacking a wet tile saw to be able to cut glass.

I'm not Drew, but at first I was reluctant to cut glass, then tried it using the scoring wheel and straight edge. Wow! It worked, and was easy. I cut the corners of my 8v10 glass, resized a piece. And, by the way, to absolutely size it is easy to sand a glass edge to fit.

Try it!
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[Jac@stafford.net]

The AR is different of the AN. See this Durst Pro lesson #13 about glass http://www.durst-pro-usa.com/resources.php?tab=13#TabbedPanels1


From the article: "A normal windowpane will over time grow thicker at the bottom than it is at the top. The larger the window and the thicker the glass the more pronounced this effect will be. The weight of the glass it self will force the glass particles to slowly travel towards the center of the earth due to gravitational force!"

That is total bullsh*t!

If it were true we would have far fewer old lenses, eh? Or imagine 'Bay kook describing an ancient lens as, "a naturally formed aspherical lens because it was always stored upside-down on the lens shade."

And it gets worse as we read on:


We are introducing cut and polished SCOTT GLASS for Durst negative holders.

The exact same type SCOTT GLASS is also used for Schneider and Rodenstock lenses.

Durst should be ashamed.

[Drew Wiley]

I've seen that Schott glass in person, though he never shipped me any with the register pins installed, so am skeptical if he had any more than a sample or two
to begin with. Anyway, Jens apparently had a bunch of Durst-labeled paper sleeves, which I assume he acquired when he bought out the leftovers when Durst closed their actual commercial enlarger production; then he used these sleeves for glass he acquired here or there. He was never connected to Durst itself, but apparently used their name by permission, as a service provider. Don't believe everything he writes about glass. I wouldn't use a tile saw unless it was equipped
with a special continuous-rim "art glass" diamond blade (distinct from a typical ceramic tile blade). ... But way back when I learned about glass hydration. It is
a scientific fact, and is some of the other molecular whatever... Only, we're talking about phenomena that need to be measured in microns per thousands of years. ... not exactly anything I'd worry about in a darkroom ... maybe if your enlarger was bought second-hand from a Neanderthal!

[ic-racer]

A few more notes on the post above dealing with cutting the Durst AN glass. The glass I used was original Durst AN glass originally sized to 5x7" and about 2mm thick. This glass cut extremely easily. It was easy to work with also. The edges were beveled to fit the carrier and the corners rounded by hand with wet 180 grit sandpaper. However, just working with this glass can scratch it, so it needs to be protected with tape while manipulating it.

I used AN glass on the top and plain Durst glass on the bottom.

[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 (http://www.invisibleglass.com/). It is the best glass cleaner and clarifier I have ever used.
.

[Tin Can]

You might want to try Stoner's Invisible Glass (http://www.invisibleglass.com/). It is the best glass cleaner and clarifier I have ever used.
.

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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