U of S | Mailing List Archive | alt-photo-process-l | Re: Gum over Cyanotypes

Re: Gum over Cyanotypes

For what it's worth I mention my own experience-- but whoever has Sara Van Keuren's manual can check the process she's used in her classes, that is, she has the students do a cyanotype, and THEN size the paper if they're going to use cyano as the blue in tricolor (or, I would assume, as a base for anything that likes a size).

I agree. My experience is that cyano is better without a pre-size.
(And that's apparently Sarah's experience too.)

When I began cyano, I tried every size I ever heard of & found that starch, gelatin (with or without hardener), spray, glue, whatever, all made an inferior print. At the time most sources did seem to call for size (tho in those early books, "info" tended to be cut & pasted from earlier books, rather than experience).

If you're not planning tricolor or a stand-alone cyano, that is, if the blue is simply a base color to be covered by other layers, the "quality" of that coat is probably less important.

Either way, if you're going to use the same negative, life is much easier if you shrink the paper first. And whether a hot pre-shrink will or won't hurt the cyano -- it's not necessary. My tests showed that a long soak at room temperature (from several hours to a day) shrank the paper as much as a very hot bath.

(However, I only tested the couple of papers I was using at the time. Can't guarantee all are the same.)

Meanwhile, I found most attempts to fasten the paper to another surface, by gelatin, drymount, sticky mount or whatever, were accident prone & generally more trouble than they saved. In the same way, perhaps, that the roots of a tree break through concrete when so inclined, a print when it's supposedly "fastened down" is nature's way of showing who's boss (and nature WANTS to buckle).

I wrote about various methods, both of personal invention & from "the literature" in some issue of P-F I forget now...(OK, I'll look for it), but the one (from an old magazine) about making an aluminum plate REALLY smooth then fastening with gelatin & releasing in hot water, was basically how to shred a good print the hard way. What I figured out was an intermediate sheet with gelatin on both sides left with an edge hanging out so you could soak in hot water, then simply pull it off. (Not to mention that you can grow old while clearing & heating up that drymount press, buried in miscellaneous and/or hogging counter space.)

As noted, it actually worked, but not foolproof, because the paper WANTS to buckle in the wash, which keeps it from washing evenly... For just re-registering without any special contrivance, I find keeping humidity constant (if possible) is a big help, but registering from the center is even helpfuller -- so any miss-register is pushed to the edges where it doesn't register that much...


On Tue, 28 Apr 2009, Keith Gerling wrote:

Carefully measure the cyanotype and then set the dimensions of you gum
negatives accordingly in Photoshop.  Print to order.

Richard Sullivan's solution - which works great - is to afix the substrate
to a surface with drymount tissue and then release it when finished.