On Fri, 3 Dec 1999, Tom Ferguson wrote:
> Also, if your "personal reason" for wanting to avoid gelatin is
> of the vegetarian type, try a layer of lightly exposed
> gum/dichromate I have never tried this, have just seen it
> mentioned on the list.
>
> I found spray starches very poor due to staining. Papermaking
> sizes (Herculon) also did poorly. Arrrowroot starch or one of
> the wide variety of starches might work (I haven't tried).
As we already know from Gerard (as if we didn't already know!) about cyano
formulas, the presumably identical materials and method can give quite
different results. With that as disclaimer, I note that I tested every
size for gum I could find mentioned, and in my tests only the gelatin
worked, although I realize in retrospect that I was testing for continuous
smooth tone in 1 coat under a 21-step. Someone doing a different kind of
printing, say 3-coat digital color gum, would have very different results.
As for instance, although diluted acrylic (1/10 to 1/12 with mat, gloss,
varnish, medium, gesso alone, gesso with varnish, Golden , Liquitex, the
whole magilla) was crummy for contone 1-coat, it was OK for 3-color
digital, although still not as good as gelatin.
Spray starch for gum, although I've heard other praise for it, was in my
tests below wretched. Spray starch will also wash out after a coat, and
be glad, because it discolors in time. The manufacturers also add funky
stuff they don't tell you about, even the same brand can be different the
next time.
I tried many versions of arrowroot and cornstarch... they will prevent
staining, but the ones I used gave a grainy texture. Charming in a way if
that's what you want. I believe they also wash off.
Aquapel didn't work... the difference between so much the emulsion
wouldn't spread and so little it did nothing may be out there beyond the
stars somewhere, but I never found it.
Joe Smieglitz swears by rabbitskin glue. I didn't do well with it (but see
above). It is also and however an animal product. Some say Elmer's school
glue is a PVA........ nevertheless, us carnivores have nothing against
gelatin. It is more trouble initially, but less in the long run.
As for the hardening coat with gum and dichromate, I've done it although
not tested rigorously against gelatin -- however speaking of trouble ....
to get out the dichromate stain enough to "read" color in the print, is
more trouble than glyoxal.
Judy
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