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Re: Gum vs. Kallitype
On Fri, 24 Mar 2000, Andre Fuhrmann wrote:
> >Now just a darn minute, Andre -- you can't drop a line like that into our
> >tea party & then take off. What's this about "glyoxal is not a very
> >effective hardener"?
> You gave the answer: not as effective as the common alternatives chrome
> alum or formaldehyd. I shouldn't want to either confirm or deny that
> length of hardening may be a factor. Seems we agree on the facts and I
> apologize if my wording may have been misleading.
No No No !! I'm not asserting that, I have absolutely NO FACTS on the
"superiority" of alum or formaldehyde for hardener, in fact only heard
that claim made once elsewhere in passing.
I simply SURMISED, correctly it seems, that that was YOUR meaning. So I
ask again -- where do you get this? How do you know? Have you made any
tests, or is this an assumption or hearsay? Equally important, what are
your CRITERIA for better??? (As noted, my own limited tests showed the
> >As for "clearing gum" in alum. Consensus of conservators seems to be that
> >alum bath degrades the color -- especially ye gods 30 minutes. (No I can't
> >document, but have read 5,627 times.)
> Depends on the color pigments. Alum does absolutely no harm to the more
> stable pigments (eg earth pigments) that IMHO one _should_ prefer for gum
> prints anyway.
Again, do you have any sources for the statement about alum?
As for what one should "prefer" for gum printing -- an interesting premise
which it would be most interesting to hear explained, tho from here it
seems difficult to do a tricolor print with earth colors. (Have you seen
the poison greens and passion purples of McDermott & McGough's gum
| Judy Seigel, Editor >
| World Journal of Post-Factory Photography > "HOW-TO and WHY"
| firstname.lastname@example.org >
(I suspect that only a very few of the common pigments are
> adversely affected by alum. Depends, of course, on what you count as
> common.) Alum has the extra benefit of further hardening the gelatine
> after the last print, thus actually contributing in one way to print
> stability. (This is why I recommended it in the case at hand.) The real
> drawback is that it is much harder to wash out than metabisulfite. But if
> the washing time has to be extended anyway when you print a kallitype on
> top, this particular disadvantage is of little consideration.
> >HOWEVER, why clearing bath for gum anyway?
> I understand that Keith used the washaid not for the dichromate for the
> hypo that fixed the kallitype layer.