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

[Bill Grimwood <bill@grimwood.net>]

I am having problems with newtons rings in my Minolta Diamage Scanner.
Where can I purchase this pumice powder.


Thanks

Bill Grimwood

At 02:27 PM 3/1/00 -0800, you 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.
>
>Jim
>
>
>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.
>>Greetings,
>
>