Re: Newton Rings

Carson Graves x4692 3NE (carson@zama.hq.ileaf.com)
Wed, 21 Jun 95 09:10:53 EDT

> From: Judy Seigel <jseigel@panix.com>
> To: Multiple recipients of list <alt-photo-process@vast.unsw.edu.au>
> Subject: Newton Rings
>
> Hello experienced ones:
>
> I used NuArc vacuum easel today to contact 35 mm negative onto TMax
> 100 sheet film to make 35mm positive; delighted with grain better than
> PCF, tone better than tech pan, etc. etc. BUT, AWFUL AWFUL Newton rings.
>
> After trying every piece of SUPPOSEDLY anti-newton ring glass in the
> drawer, I dug up glass negative carrier that did cut them out,
> though I had to jury-rig it (great phrase, these days!) to give adequate
> pressure & contact (I hope -- will see when film is dry).
>
> But -- isn't there something I can do to cut out Newton rings from the
> vacuum easel (besides calling Chicago tomorrow)? A sheet of mylar? Acetate?
> I've heard of baby powder (or maybe it was cornstarch), but am having enough
> trouble trying (failing) to keep neg & glass clean.
>
> The original negative, incidentally, is on FP4. I cleaned off some
> gunk with film cleaner, which of course left its own film, which I wiped off
> with anti-static cloth. Maybe that made shiny surface to cause
> trouble?
>
> Thanks for any info.
>

Here is the traditional method for eliminating Newton's rings as
practiced by printers making color separations back in the days before
computers & when dye transfer was the perferred way to make prints for
magazine reproduction:

They used to use something called "lithographer's dust" which was more
of a technique than a product. (Apparently there once was such a
substance, but about 15 years ago I called around to many printing
supply houses asking for it, and all I got was the telephone equivalent
of a blank stare.)

The technique is to place a small amount of a fine powder (Baby Talc
works well, corn starch powder should be OK too, although I think I'd
stay away from the medicated stuff - just try to get the most pure
product you can find on the drug store shelf) in a plastic squeeze
bottle with a nozzle. A plastic ketchup bottle would work well, but it
doesn't have to be that big. The goal is to have roughly an ounce of
powder in a volume of about 12 ounces i.e. lots of air space. Then,
give the bottle a short shake and set it upright on a flat surface.
Wait at least 30 seconds for the heavier particles to settle (the
longer you wait, the finer the dusting you give your negatives). Then
carefully lift the tip of the nozzle so that it is an inch or two above
the negative (the bottle should be mostly upright - no more than a 45
degree angle) and give the bottle a light squeeze. If you look closely,
the "poof" that comes out will settle a very fine pattern of dust on
the negative surface. You can repeat if necessary, but once you get the
hang of it, one time should be enough.

The dusting is what prevents the close glass/negative contact and
prevents the Newton's rings. It is almost invisible, and you can clean
it off with a soft brush.

One other thing, I've found that Newton's rings are very weather
dependent, especially with changing humidity conditions. I always had
more problems with them when the humidity was high, but that may have
been a function of the equipment I was using. It is worth changing the
humidity (high or low) to the opposite condition to see if that helps.

Good luck,
Carson Graves