Re: was Re: Gum print formaline, now glyoxal yellowing

When we discussed this same issue in spring last year I sized some
samples Canson Fontenay, the paper I am using for gumprinting. Sizing
was done in a tray with a 3% (grocery) gelatin solution. I hardened 4
samples and the left one unhardened and added one unsized sample. All
papers where not showing any yellowing when dry.

Samples were hardened as followed:

sample 1: unsized, unhardened
sample 2: sized, unhardened
sample 3: sized, soaked for 3 minutes in 1 liter water with 15 ml
formalin(37%), dried
sample 4: sized, soaked for 3 minutes in 1 liter water with 15 ml
glyoxal (40%), rinsed for 5 minutes in running water, dried
sample 5: sized, soaked for 3 minutes in 1 liter water with 15 ml
glyoxal (40%), dried
sample 6: sized, soaked for 3 minutes in 1 liter water with 50 ml Maco
Geladur (this is a 2.5 - 5% glutaraldehyde solution), dried

Note: probably the glutaraldehyde concentration could have been lower.

Then I dated all samples (April 11, 2004) and put them in individual
black plastic envelopes in a dry place at room temperature. Today I
decided to open them.

At first sight one sample (# 5 - unrinsed glyoxal) had yellowed
completely and one (# 4 - rinsed glyoxal) yellowed only at the bottow
where there was a gelatin buildup.
After this visual inspection I took readings with my color densitometer
(old X-Rite 310X)

These values (M, C, Y) I measured:

sample 1: M 0.06, C 0.06, Y 0.07
sample 2: M 0.06, C 0.06, Y 0.07
sample 3: M 0.06, C 0.06, Y 0.12
sample 4: M 0.06, C 0.06, Y 0.08
sample 5: M 0.06, C 0.06, Y 0.07
sample 6: M 0.06, C 0.06, Y 0.07

Conclusion: with this paper there is a significant yellowing when
hardened in glyoxal and left unrinsed. Unhardened gelatin does not
yellow. Maybe this could change when exposed to light. There is a slight
measured yellowing (but probably not significant) on the surface and
some yellowing at the edges with the rinsed glyoxal sample.
I did not try printing gum on glutaraldehyde hardened paper yet. Glyoxal
and formalin hardened papers behave similar. I am using the rinsed
glyoxal method for several years now and will probably keep using it.

kees

Christina Z. Anderson wrote:

> Judy said:
>
>> Meanwhile, I mention again that when I RINSED after the hardening
>> bath, I had NO YELLOWING. That doesn't solve the problem for folks
>> who put the glyoxal in the gelatin... but it might encourage a
>> different protocol ?
>
>
> Mine rinsed right away still yellowed. Hmmm.
>
>>> Robert said:
>>
> am using glyoxal on the same papers without yellowing problems. My
> workflow is too print the canyo layer (usually 12 to 14 for the week).
> I then use three coats of gelatin and harden after the last coating
> (soaking the paper in gelatin). As soon as the paper is dry I begin
> the gum layers. It maybe the gum layers and washes take care of the
> yellowing?
>
> Who knows? It seems the sitting around of the paper after the glyoxal
> is put on does the deed, and if you are using glyoxal and then
> printing immediately...but if I remember correctly Clay got his
> yellowing in a week, or even 5 days.
>
> I usually size 30 16x20's at a time and it'd be difficult to use right
> away. I also size under my cyano layer.
>
>>> Don said: I do have a question for Chris though. How do you hang
>>> your paper to dry?From a single corner leaving a corner pointing
>>> straight down or along the
>>
> top edge like a towel or sheet?
>
> Two clothespins, so my beads of yellowing are all along one edge.
>
> Don asked: Are you using baking soda with the glut Chris?
>
> Never use baking soda with any of the sizes...
> Chris
>
>
>
Received on Mon Jan 31 09:45:23 2005