[pure-silver] Re: Some Edwal Patents

Hello Richard,
How does one go about finding the patents that correspond to the numbers that you give below? I'm Canadian so I am not familiar with the workings of US Federal Offices. I tried a google search but that didn't work.
If you could point me in the right direction, it would be very much appreciated. Thank you. 

Cheers,
Bogdan

Richard Knoppow wrote:
A mention of an Edwal developer in a recent post to rec.photo.darkroom reminded me to conduct a patent search for Edwal products. I found two Edwal patents which may be of interest. One is Edmund Lowe's patent for extra-fine-grain developers. He gives examples of developers containing Ammonium Chloride as the fine grain agent. Since Microdol-X and Perceptol are similar types but using Sodium Chloride I think this patent is of considerable interest. It is USP 2,164,280 The other patent is a later one for general fine grain developers using Metol and Glycin. It is USP 2,374,921 Another patent that showed up in the search is one assigned to H&W and probably is for their "Control" developer for high contrast film. H&W sold a microfilm type film for super-fine-grain pictorial use under the name H&W Control with a special pictorial contrast developer. This is similar to Kodak's Technical Pan and Technidol. The developer may still be of interest for those who want to use thin emulsion microfilm for pictoral purposes. 
It is USP 3,772,019


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Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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________________________________________________________________
  Bogdan Karasek
  Montréal, Québec                     bogdan at bogdanphoto.com
  Canada                               www.bogdanphoto.com

                  "I photograph my reality"
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