Re: report on glyoxal yellowing

On Wed, 10 Nov 2004, Christina Z. Anderson wrote:

> All samples showed consistent yellowing, and the yellowing was the worst
> in the hot press and cold press for all sampled conditions

CUT
> I can deduce (I think) that paper type is a factor. It makes no sense
> that the bumps would be the factor, since cold is bumpy, hot is not and soft
> press is in the middle yet the whitest, so the papers must have something in
> them different. My feeling that the alkalinity of the paper is the factor of
> whether the glyoxal yellows or not is probably something I should test. I
> have felt this way since Judy mentioned that baking soda added to the glyoxal
> solution turned it bright orange (if I remember correctly)....

Actually, baking soda did the least color change, slight enough so that I
could use it, tho I decided the theoretical increase in gelatin stability
was ... only theoretical -- not seen to make a difference in actual
printing. The strongest color change was sodium carbonate, tho most other
alkalis I tried were almost its equal.

For what it's worth, I believe that sodium carbonate is what they "buffer"
paper with. If I understand you correctly, you haven't tested on any other
manufacturer's paper..? I have normally used various Fabriano papers,
including the artistico, also the satista, and one called 50/50 (half rag,
half not), etc., tho always the hot press. These may have yellowed before
I began rinsing, but none of them yellowed since, or not that I have
noticed.

> As far as time factor, I noticed a bright orange bead of gelatin on the
> edges of my paper within several weeks. I'll see if it disappears in doing
> my gums.

The mystery, if anything, deepens...But now, Chris, that you've
volunteered, don't you think you need to make these tests somewhere ELSE ?
(New York maybe?) My own experience, meanwhile, is that the orange color
washes out with a long-enough soak -- but who knows what will happen south
of the Mason-Dixon line?

However, it does occur to me to ask what strength of glyoxal you rinsed
with. I use 15ml per liter of water, which my tests showed hardened as
effectively as 25 ml. But I wonder if that difference could affect
yellowing?

Judy
Received on Thu Nov 11 20:51:20 2004