Re: [Leica] Re: Solutions for avoiding newton rings

[John Collier <jbcollier@home.com>]

I assume hobby shops that carry rock polishing stuff would carry it. Since
you do not know the affect this will have on your scanner, make sure the
glass is readily available and easily changed.

John Collier

> From: Bill Grimwood <bill@grimwood.net>
> 
> I am having problems with newtons rings in my Minolta Diamage Scanner.
> Where can I purchase this pumice powder.
> 
> 
> At 02:27 PM 3/1/00 -0800, Jim wrote:
>> Newton rings are caused by imperfect contact by part of the film with
>> glass. Film with more curl are more prone to newton rings. Current humidity
>> also is a factor as to the severity of the problem.
>> 
>> One solution is, of course, to eliminate all contact between film and
>> glass. This is why glassless neg carriers are so popular.
>> 
>> Many years ago (1950's) Kodak recommended rubbing the glass (that which has
>> contact with the film) with fine (00) pumice powder using cotton. This
>> basically makes the surface layer of the glass, less "glazed" so that the
>> type of film/glass contact, producing newton rings, does not take place.
>> The use of 00 pumice powder makes no humanly observable difference. But it
>> makes a difference in how the film base and glass get along.
>> 
>> 
>> 
>> At 09:59 AM 3/1/00 +0200, FB wrote:
>>> Thanks a lot for your help in solving my newton-ring problem.
>>> First of all I was wondring why Leitz made enlarges which were Newton
>>> sensitive. The answer is that they were not newton-sensitive with the
>>> emulsions of the 50's and 60's. They were not that thin and glossy.
>>> The solutions can be divided in two groups :
>>> 1. Anti-newton glass
>>> - Leitz anti-newton glass but the Leitz anti-newton glass is hard to
>>> find (impossible ?)
>>> - Make anti-newton glass yourself with the AN-glass of a 6x6 slide
>>> frame. That must be a good solution but glass doesn't cut as easily as
>>> paper and make sure the edges do not scratch the negative.
>>> 2. Avoiding contact between the negative and the condensor.
>>> - Tape of the 24x36mm frame and make sure the tape is not too thin
>>> (the misake I made).
>>> - Make a frame to put on the negative stage with a 24x36mm cut out. I
>>> made it out of medical film.
>>> I am working with the last solution now which works very well for me.
>>> I also have the feeling that it is more forginving for dust on the
>>> negatives.
>>>