Can a ground glass substitute for Anti-Newton-Ring Glass?

[Hugo Zhang]

Yes, 8x10 printer has a space for 10x12.

My poor memory. My 8x10 contact printing frame has an ANR glass with a measurement of 223mm x 274mm.

[Sal Santamaura]

My poor memory. My 8x10 contact printing frame has an ANR glass with a measurement of 223mm x 274mm.

Which is about 8-3/4 by 10-3/4 inches. Depending upon how wide the frame rabbet upon which that glass rests is, it could be perfect. As long as the frame doesn't mask an 8x10 negative, which is slightly less than 8x10 inches, you might have something even better than 10x12, especially if the frame's rear opening is just large enough to accept 8x10 paper while centering it on the glass. Such a configuration would eliminate all the fussing to align negative and paper.

[Hugo Zhang]

Which is about 8-3/4 by 10-3/4 inches. Depending upon how wide the frame rabbet upon which that glass rests is, it could be perfect. As long as the frame doesn't mask an 8x10 negative, which is slightly less than 8x10 inches, you might have something even better than 10x12, especially if the frame's rear opening is just large enough to accept 8x10 paper while centering it on the glass. Such a configuration would eliminate all the fussing to align negative and paper.

The glass is actually a little bigger with usable area about 8 3/4 x 10 3/4 inches.

[Drew Wiley]

I have zero alignment issues with 8x10 film because I use the same pin registered contact frame for contact printing as for masking purposes. Its overall AN plate glass size is about 10X12. Laying around in storage I have a full 16x20-ish contact frame which I inherited but never even used; but I do recollect putting a sheet of AN glass in it too, though might have later cannibalized that same sheet for a different application. Regardless, I'd need a cordless indoor bulldozer to find it that antique mahogany contact printing frame.

[RichardRitter]

Over the years of printing in the same darkroom I have found that I would have problems with Newton rings and then go for months with out any problems. Winter time was the problem time. the dark room would be below 40 % humidity and sometimes as low as 15%.

[Tin Can]

Does the pressure PSI used make a difference?

I have 3 high pressure contact printers with no problems

[Michael R]

To make a long story short, the formation of the Newton ring interference pattern requires two things: (1) imperfect contact ie places where there are extremely thin air gaps and other places where there is direct contact, (2) non-scattering reflection between the two surfaces.

Regarding an example of item (1), suppose you have an area of extremely thin non-contact with a contact spot in the middle. The Newton ring pattern will radiate outward from the contact point. The rings have to do with the relationship between the thickness of the air space and wavelengths of light. As the air space increases from zero moving outward from the point of contact, the rings are the alternating interference from the light reflecting between the surfaces.

So, it is not the amount of pressure per se. Contact is contact. To the extent more or less pressure either improves or worsens item (1) above, it can either help or cause problems. It depends.

Does the pressure PSI used make a difference?

I have 3 high pressure contact printers with no problems

[Oren Grad]

So, it is not the amount of pressure per se. Contact is contact. To the extent more or less pressure either improves or worsens item (1) above, it can either help or cause problems. It depends.

The issue is distribution of pressure, and the problem is that the devices most often used to impose pressure - typically, springs arranged in various ways on the removable back of a printing frame, with the back often covered with a layer of felt - don't provide it anywhere near evenly. No, the wooden back and the felt don't spread the pressure around all that well.

I've always had issues with Newton's rings in my darkroom with any spring-backed frame I've ever used. I've had best luck skipping the frame, just building a stack with a thin piece of glass sitting on the enlarger baseboard, then paper, negative, and finally a thick piece of glass, substantially larger than the paper, on top. Yes, the top glass, negative and paper need to be handled with every exposure. C'est la vie, haven't yet found any other way that works enough of the time.

Long ago I did some experiments with coated AR glass, with inconsistent results. I eventually gave up because I was driving the local pro framing shop crazy searching for large enough pieces without coating flaws that would be visible in the prints. Maybe the production process and handling methods for AR glass have improved since then.

Tried various textured glasses too, but the texture always showed up in the prints.

Finally, a big YMMV. None of the above is to say that my approach is the correct one and if only you do the same, you will have no problems. This is so exquisitely dependent on local conditions that there's no alternative to just trying different approaches until you find something that works for you.

[Tin Can]

I wish we had some Fuji Prescale Pressure sensitive film

https://www.sensorprod.com/campaign/...gaAq66EALw_wcB

We could quantify what works

I used it for decades

I use a NuArc vacuum press with what must be tempered glass. The rubber bottom has many many vacuum suction holes

It bends the glass, I also add a large matt board under the neg, then top with printing paper and neg neg

For 8X10 and smaller I use a 1940's printer with lamp under the stack. It has a big hard pillow that forces the neg and print together. Works fast for multiples.

I am still working with a 20X36" 3/8" tempered glass for gravity printing long negs

I am inspired by the very long contact prints made with Circut film cameras

https://en.wikipedia.org/wiki/Cirkut_(camera)

[Drew Wiley]

This foggy coastal climate is Newton Ring Hell. It sure doesn't help that some modern films are just so darn slick - Acros and Delta 100 being among the worst, and TMax often problematic too. I lust for the good old days of retouching "tooth" surfaces on sheet films. Kodak's current color sheet films have a scanning-improvement overcoat which helps. But roll films, yikes! Aerosol AN spray cans have gone the way of dinosaurs, probably due to enviro nasties in the propellant.

This time of year I have to up the utility bill a little and pre-heat the enlarging room well in advance, to prevent any condensation; and I pre-heat the cold light too, if that particular enlarger is the one being used.

Right now, despite the stunning amount of rainfall we've had in the last two weeks, rings have not been much of a logistical problem, giving how I routinely use AN glass. But ironically, once things start warming up later in Springtime, all that moisture in the soil starts turning into humidity and abruptly ends certain kinds of darkroom tasks, especially seasonal masking or film duping work, which really tempts Newton Ring formation somewhere in the cumulative exposure sandwich.

The micro-dimple pattern of certain Otho Litho films like current Arista not only helps efficient drawdown under a vac blanket, but is an excellent way to defeat N. Rings as well. Too bad it's so miserable for general shooting.