Re: Gum print formaline

Christina Z. Anderson wrote:
>

>
> One thing I was thinking about with sizing: I think I mentioned a while
> back a speckling stain on the third coat (magenta) on glyoxal sized Rives
> BFK paper. Don had that exact thing on his gum prints on Rives. I just
> want to throw this observation out there: with glyoxal, the gelatin feels
> "gritty" to me on the surface of the paper. With glut, it feels smooth.

Does anyone have any information re relative amounts of glyoxal and
glutaraldehyde required to produce an equivalent degree of
crosslinking? What I'm asking is, there any way of knowing whether 25
ml (which Chris reported using in her glyoxal tests) or whether 15 ml
(which Judy reported in that thread is what she uses and which James
recommends) or whether some other amount of glyoxal per liter of gelatin
produces approximately the same amount of crosslinking in gelatin as 6
ml of 2.5% glutaraldehyde per liter? Is it possible that the difference
between the grittiness Chris reports with the glyoxal and the smoothness
she reports with glutaraldehyde could be due to a simple difference in
the amount of crosslinking produced by the two substances at the
concentrations used?

I've never hardened gelatin with glyoxal and have no opinion whatever
about its use for that purpose, but I have crosslinked a lot of
unpigmented gum by the dichromated colloid process and I've hardened gum
with glyoxal; my observation from these two activities is that at a
certain point, gum is hardened enough that it can't be dissolved with
water, and that more crosslinking beyond that point results in a very
gritty, crystalline surface. Thus my question, although of course it's
certainly possible that gelatin and gum behave differently in this
respect.

Katharine Thayer
Received on Mon Jan 31 00:05:28 2005