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Bob Salomon
22-Apr-2004, 11:43
Why is the pressure unven?

Are you using any kind of frame to hold the sandwich flat?

Does it happen with a piece of float glass on top?

Have you tried any of the AN sprays or corn starch etc?

Michael Mutmansky
22-Apr-2004, 11:57
Michael,

I presume you are using some kind of print frame to do this contact printing? You may need to put another layer of felt in the back to get a bit higher pressure on the sandwich.

Are you putting the mask under the film (between the film and the paper)? This should leave the film solidly against the glass, which may or may not be beneficial. One thing you can try is to reverse the order of the mask and film. That may give you better conditions to remove the newton rings.

I have never noticed newton rings in contact prints, but they are plainly visible on the film to glass interface when the sandwich is made. However, I don't typically print on silver paper in this arrangement except for proofs, and I don't look at these too closely, so they may exist in my conditions too.

Lowering the humidity in the darkroom may help it a bit, as it is trace moisture that creates the newton rings in the first place.

---Michael

Ralph Barker
22-Apr-2004, 12:45
Depending on the thickness of the glass, and the collimation of your light source, you might try putting the rubylith on top of the glass. That might soften the edge of the white border, but it might be OK. Alternatively, a piece of clear acetate, the same thickness as the rubylith and carefully cut to fill the opening in the rubylith might also solve the problem of less-than-even pressure on the negative. Unfortunately, that adds two more surfaces for dust problems.

Merg Ross
22-Apr-2004, 13:43
I would suggest using litho tape on the edge of the glass to accomplish a white border and dispense with the Rubylith. This way your negative will be in direct contact with the glass and should prevent the problem you are experiencing.

Henry Ambrose
22-Apr-2004, 15:00
Would anti-newton ring glass help?

Oren Grad
23-Apr-2004, 15:43
Michael -

I've done extensive experiments using mylar (silver) tape on glass to create masks for clipping borders or otherwise cropping in contact printing, but never managed to get Newton's rings reliably under control. To keep the negative positioned where I want it relative to the mask needs a dab of some sort of removable tape, but uneven pressure resulting from the thickness of the tape has been enough to cause trouble.

I have some of the Tetenal anti-Newton spray. I've experimented with it on the glass, without much benefit, but haven't had the nerve yet to actually cover a negative with it, and I don't know if I ever will. I don't care to breathe the stuff either.

I wouldn't dream of putting cornstarch on a negative - can't imagine how I'd ever get it clean again.

There is another approach if you run out of ideas - use a different film with a base that has more inherent texture, like the old TXT used to (don't know about the new TXP sheet films), or like the current Bergger BPF200. (I know, that can be a big hassle if you really like and have adjusted to the sensitometry/tonality of HP5+. That's certainly a problem I have.)

Sorry my own experience doesn't provide much encouragement, but good luck - and do let us know if you find a fix you're happy with.

Henry - in most cases anti-Newton glass is unusable for contact printing - the pressure required results in the print picking up the grain of the textured glass surface.

Oren Grad
23-Apr-2004, 15:53
Michael -

Sorry, I should have said I wouldn't dream of putting cornstarch on the glass either. At least in my hands, anything that's on the glass and not fused with it will end up messing up the negative too... < g >

Alan Shulik
28-Sep-2004, 17:40
I have been doing platinum-palladium contact printing of 8x10 and 16x20 negatives onto Gampi paper (a very thin, translucent, hand-made Japanese paper). I recently encountered the problem of newton rings when I began using my 16x20 contact printer. (I'm not sure why the 16x20 contact printer caused rings when the 8x10 contact printer did not, but there must have been some difference in the glass.) In any event I solved the problem very easily.

Platinum/palladium contact printing is done under a very hot, 1000 watt bulb for several minutes. There is a strong fan that keeps the bulb cool in the exposure apparatus I use. Nevertheless, I believe that the solution could generalize to silver contact printing.

I tacked a sheet of translucent gampi paper onto contact printer, covering completely the outside glass. (I tacked it so the fan wouldn't blow it off!) I extended exposure by an additional 1/3 time. The newton rings were eliminated every time. Prints were beautiful.

I think you might try using any translucent/diffusing paper, possibly even wax paper that you could buy in a supermarket, as long as it has an even surface consistency. Or a sheet of translucent plexiglass might work as well. Make sure that the negative is completely covered by the diffusion paper. Extend your exposure time, or use a larger F stop on your enlarging lens, to compensate for the light absorbed by the diffusion paper.

I am interested in learning if this solution works for you. It's certainly quite easy to test....

PS My images viewable at Ashulikphoto.com.....

John Kasaian
28-Sep-2004, 19:42
Awhile back I bought a piece of anti newton ring glass(sounds like something from Lord of The Rings or an old Republic serial!) salvaged from an enlarger used to blow up 9-1/2" aerial roll negatives from an eBay seller---I think called "eyepec" for about 15 bucks--- and transplanted it into my elderly Elwood. Apparently he gets a lot of optical stuff from the government and aerospace industry thats quite useful for "shadetree" enlarger mechanics like me. It might be worth checking out to see if he has any more pieces of the stuff.

Good luck!