> But what about scanning say a salt print (or other alt-processes) with a
> HP Scanjet 4c (or probably worse: a photocopier)?
>
> Is there someone on the list knowing anything on that specialised
> subject? (Recommandations, reports, density readings before and after
> exposure, etc.) Looks like a difficult item. There are so many
> variables: I.R. U.V. intensity, duration, kind of process, the effect of
> sudden local changes in Lumen and heat, etc.
There was a conservator I talked with some time back on the photogenealogy
mailing list, who had some data showing possible damage to albumen prints
from Xeroxing the print. He sent me his densitometry data, I think I
might be able to find this or his e-mail at least.
You are correct in noting that there are a large number of variables
possible, and that showing causality would be difficult. The guy I talked
to had tried to approach the problem by identifying the technical
specifications of the scanners and copiers currently on the market, but
found that this information was next to impossible to compile. To this
end, I got thinking about creating a designed experiment using a
fractional factorial screening approach. We'd need to collect samples of
scrap prints or test strips from as many processes as possible, and get
volunteers to scan or photocopy these samples. These samples could then
be tested for density shifts. This would only indicate what processes
would be affected by what scanners or copiers, and to what extent. It
wouldn't identify the physical mechanism at work.
- Wayde
(wallen@boulder.nist.gov)