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Im printing color negatives with a dichroic enlarger and use a glass sandwich negative carrier with anti newton glass on the top element. Ive used the same carrier with b&w with no rings but color printing seems to change something. All my prints come out with a large amount of newton rings. Any explanation to this?
Shiny side of the film against the bottom glass of the glass sandwich?
Normally the base side is the one that gives problems, but with some films the emulsion side can be shiny enough that it give Newton's rings as well. Try removing the bottom glass of the carrier. Many time you can use a top mask (as it has no metal alignment pegs) on the bottom in place of the glass. In other words, use the top part of a glassless carrier on the bottom, with opaque tape over the alignment holes. As the negative heats, it'll bend up towards the light source. The anti-Newton glass will keep the negative flat, and since there won't be any glass on the bottom, the emulsion side won't cause any rings. If you still get rings, then for some reason your AN glass isn't being effective.
high ambient humidity? You could try hitting both with hot, dry air from a blow dryer and see if that solves your problem.
In the foggy coastal climate here I generally have to use AN glass both top and bottom for color film, or for certain relatively slick b&w films. This seems preferable to using an antinewton spray or powder, though you could try that too. With the right
combination of AN glass type and enlarging lens/magnification ratio the pattern of
the glass shouldn't be apparent at all, even in very critical work. But it might take a little experimentation to fine tune things.
Poscript - I'm a strong believer in glass on both sides of the neg; that is, if you care
about sharpness, it has to be kept completely flat and unable to bow or buckle in
either direction.