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Dmax measurements of several papers.

Agfa Lupex paper was a good example of the use of all of the then-current chemistry to get good black tones using addenda. Brovira was another.

Kodak Azo and Kodabromide were similar in nature to these, but the pure Lupex gave an excellent black tone image with no addenda whatsoever.

PE
 
I was very impressed with the low fog of the 1946 sample. Using the same densitometer and mode the old paper measured only log 0.04 more than the new sample. Frankly I had no idea at the time that any paper that old could have such low B+F so I was pretty shocked when I first did the tests. Since then I have heard from a number of people who have found relatively low B+F levels in very old AZO samples.

Sandy



 
What would be also interesting to me is, to strip the emulsion off the 1926 and 1936 emulsions and look at the crystal structures under scanning electron microscopy, and compare that to today's Azo. I don't see much new technology in that area in 1930s but whether today's Azo is made in the same way or not could be argued on a more sound basis.
 
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