All the carriers I have used a bevel is required.
With Museum Glass we have found that regular cleaners will ruin the surface.
Originally Posted by ChuckP
But....... My lab has a frame shop attached to it, we purchase really good AR and Museum glass and I can sell some off cuts really cheap or even give away some small off cuts to those
wanting to try AR glass verses regular glass from Focal Point... it will not be bevelled or cut to specific sizes as we are busy with Contact Photo Festival right now.
What do you mean "required"?
Originally Posted by Bob Carnie
I wouldn't want museum glass below the negative. Perhaps above the negative if it helped cut down on Newton rings, which I doubt.
Originally Posted by ChuckP
Sponsored Ad. (Subscribers to APUG have the option to remove this ad.)
Regarding question #34 “Required bevel on carrier glass”
Most carriers have retainers that grip the 45-degree bevels of opposite edges of the glass. The retainers must generally be made so that they don’t quite reach the mating glass surfaces between the two plates. Otherwise the retainer would interfere with the opposite glass preventing the carrier from being fully closed and the interference could damage or even break the opposite glass. Too, if the retainer stuck up too far it might also bite the negative, ruining it.
"Museum" glass is sometimes laminated with a UV polymer film. Don't try that. The titanium coated
type is very clear and color netural. The biggest problem with this stuff is that it needs to be cut
like temepered glass, with a different cutter geometry than window glass, that it forms very sharp
edges, and that it is fairly fragile. You clean it with the same care as a lens; but the coating per se is not soft or easily scratched. It will chip if you try to ease the edge with a regular glass router.
Instead take a very fine sanding sponge (nice thick one, so you don't get cut) or some 600-grit
wet/dry emery cloth or crocus cloth and sanding block, and gently relieve the edges of the sides.
Just with the mfg website regarding the suitable cleaning solutions for the specific product. They
differ, due to different coating methods.
I wanted to update this thread with some preliminary results of a couple of experiments with optical glass for enlarging carriers. Appreciate any feedback, suggestions for other types of glass, etc.
Just to recap, I had been thinking about full glass carriers in which we have glass below the negative, and why we usually don't think about the quality of the glass. Further, would it be possible to reduce or eliminate the intermittent problem of Newton Rings in enlarging and contact printing by using coated glass. This would be nice for two reasons: a) It would reduce/eliminate the need to use sometimes problematic etched anti-Newton ring glass above the negative, b) it could help prevent Newton rings from forming on the emulsion side of certain films such as the TMax films which have a glossy emulsion surface. I wanted to try several different types of anti-reflection coatings.
Experiment 1 involved replacing both the top and bottom glasses in a 35mm carrier with 2mm clear, multi- resistant-coated ("MRC") optical filter glass from Schneider's top-line B+W filters. As expected, light transmission was improved (who cares really), and the extremely hard MRC coating is a breeze to keep clean and very resistant to scratching. Unfortunately Newton rings are not eliminated – even on the emulsion side of TMax and Fuji Acros, but they do seem to be significantly lessened. The major downside is the price of this glass, even for a 35mm carrier. Also, the MRC glass is not available large enough to accommodate anything bigger than a square medium format negative.
Experiment 2 involved replacing both the top and bottom glasses in a 4x5 carrier with 3mm clear, coated optical filter glass from Schneider’s Motion Picture division (they custom cut and bevel filters for movie/TV cameras etc so they can make larger sizes). The anti-reflection optical coating is different than MRC. The results seemed to be the same as in experiment 1, although this glass is not quite as expensive, and is also available in different thicknesses.
Experiment 3 was the same as experiment 2 but using Miroguard anti-reflection coated framing glass from Schott. Same results.
Awaiting receipt of anti-reflection and anti-glare framing glasses from Tru-Vue. I am curious to try their coated glass. I am also interested in potentially using the anti-glare glass on top of the negative either in enlarging or contact printing. The anti-glare glass has a slightly roughened surface. The effect should be similar to etched anti-Newton ring glass, but perhaps the texture will be finer, which could potentially be less problematic than with some anti-Newton ring glasses, where a faint texture can sometimes be visible in smooth tonal areas of the print. If the “texture” is fine enough, it might also prove useful in some condenser enlargers. I’ll have to get some Focal Point anti-Newton ring glass to use as a reference point. Framing glass is much less expensive than optical filter glass.
There are scattered reports of specific anti-Newton ring coatings (mostly in the world of touch panels etc, but also optics). That would be fun to investigate.
In addition, one would think a “nano-particle”-type optical coating (such as Nikon’s Nano Crystal Coat, and some other coatings I’ve read about) could be useful in reducing or eliminating Newton rings.
For now though, the only solution which seems to work all the time, is simply placing a fixed (clear) sheet of Tri-X 320 between the top glass and the negative. This is great for contact printing too, and eliminates the need for anti-Newton ring glass above the negative.
The more vexing problem remains underneath the negative in an enlarging carrier, with films like TMax that have shiny emulsions. I have been corresponding with John Sexton on this over the past several months as it turns out he has been intermittently performing similar anti-Newton ring experiments with TMax . I will pass on any results (although for now he’s paused on these tests since he’s currently not getting Newton rings). Indeed, I have also found Newton rings to be an intermittent problem, which makes it that much more difficult to solve.
This may be the right thread for my problem even if it doesn't concern Newton rings. When I enlarge negatives , full size with the black border, using a glass neagative carrier with glass on both sides the following happens. If there is a highlight area that extends all the way out to the edge, I get a thin dark shadow on the picture area along the edge. I have a feeling that this is some kind of a "light piping" phenomenon caused by the difference between the transparent film surrounding the negative and the almost totally dark highlight area. It appears mostly on my Leitz Focomat IIC with an Ilford 500 multigrade head but also on the Durst 805 B/W with condenser. If I use glasless carriers it doesn't occur.
Does anyone recognize the problem and do you have a suggestion for a cure ? Thank you in advance.