[pure-silver] Re: paper speed variation

"Don Sweet" <don@xxxxxxxxxxxxxxxx>
What an interesting suggestion about paper aging, that it starts from the
date you open it rather than the date of manufacture.

It is just an observation.

I do a lot of quasi-sensitometric testing of paper for the
Darkroom Automation paper speed charts.  When opened the papers
from different emulsion lots can have the same speed within 0.1 stops*.
However paper opened six months ago is always ~ 0.5 stops slower
and ~1/4 grade softer than it was when opened.  This is not,
however, sufficient proof.

Notes *: For Ilford, best case. Other brands have greater variation. Forte papers have varied by a 1/2 stop of speed within the same box.

==
Nicholas O. Lindan
Cleveland Engineering Design, LLC
Cleveland, Ohio 44121

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