It should be noted here that there is a difference in the way chemical
compounds are added to the *manufacture* of paper and the way they are used
in processing photographic papers.
In the manufacturing process, most compounds remain in the paper fibers.
There are books that thick on fillers, opacifiers, etc. They make it
abundantly clear that most chemicals are meant to stay there.
Photographic processing, on the other hand, uses chemicals that play a
certain role in the image forming/binding process, to be washed out later.
By the time a gum print has been cleared of its dichromate stain, it is
pretty safe to say that most other water soluble compounds used in the
process have been washed out.
>it is debatable as to the "real life" effects it can have on good
>papers (like BFK and other cotton rag artist papers) regardless, I
>would recommend that if the longevity and archival quality of your
>work is important to you, you should avoid using alum in place of
>gelatin size.
Alum cannot be used in place of gelatin size. It can be used to harden (or
tan) gelatin and then can be washed out but it cannot replace gelatin since
it is not a colloid and it is for this purpose that we need gelatin in the
first place.
Luis Nadeau
NADEAUL@NBNET.NB.CA
Fredericton, New Brunswick, Canada
>
>One other note on 20 x 24" negative production and the xerox machine,
>you can run polyester sheet through some xerox machines, so it may be
>worthwhile to investigate that as an option if you are willing to wax
>or oil paper negs.
>
>Deborah