Odd Gum Bichromate Problem

[Colin Graham]

Has anyone using glutaraldehyde notice a distinct sliminess in the sizing? I've used amounts of 2.4% (diluted from photo formulary 24% stock) ranging from 1 ml to 4ml per 100ml of 3% 250 bloom size and the gelatin always swells and get very slimy regardless of concentration once the print in is the developing water. The size doesn't wash off outright, but the gelatin does seem to be getting reconstituted, and feels very fragile. Is this typical? I keep reading it can be used once dry, but maybe it just needs to cure longer. I never noticed this with glyoxal, once hardened it never seems to get really slippery or swell up, no matter how long it soaks.

I also noticed that the stronger the dilution, the more amber-colored the sizing solution and in turn the more yellow the paper is once dried. Much more yellow than with glyoxal. Maybe the stock is bad? If it helps any, I can't smell this stuff at all in the 2.4% dilution- I haven't taken a really good snort, but it's odorless during ordinary working conditions. I did use a respirator mixing from the 24% concentrate.

[donbga]

Has anyone using glutaraldehyde notice a distinct sliminess in the sizing? I've used amounts of 2.4% (diluted from photo formulary 24% stock) ranging from 1 ml to 4ml per 100ml of 3% 250 bloom size and the gelatin always swells and get very slimy regardless of concentration once the print in is the developing water. The size doesn't wash off outright, but the gelatin does seem to be getting reconstituted, and feels very fragile. Is this typical? I keep reading it can be used once dry, but maybe it just needs to cure longer. I never noticed this with glyoxal, once hardened it never seems to get really slippery or swell up, no matter how long it soaks.

I also noticed that the stronger the dilution, the more amber-colored the sizing solution and in turn the more yellow the paper is once dried. Much more yellow than with glyoxal. Maybe the stock is bad? If it helps any, I can't smell this stuff at all in the 2.4% dilution- I haven't taken a really good snort, but it's odorless during ordinary working conditions. I did use a respirator mixing from the 24% concentrate.

I use glut exclusively and I've never had this problem. Seems I recall that there maybe some sulfide additive to the Formulary glut but I really don't know.

No yellowing ever with glut.

I add 6.5 ml of 2.5% glut to 1 liter of a 3% gelatin solution. I also add pure grain alcohol, 50ml per liter to reduce sparkles. I use 250 bloom gelatin purchased from Bostick & Sullivan.

And yes more concentrated solutions of glut will cause yellowing. Chris Anderson has tested this thoroughly and she maybe using Formulary glut since she teaches gum workshops there.

[Colin Graham]

Thanks for the info Don. I might actually be over-hardening, since the least amount I've used is more than your concentration. I'll try less.

Who's your supplier? If it comes to that I might try another source to see how it compares, but PF is the only place I've seen it.

[Loris Medici]

Less won't help I presume; since less hardener = less crosslinking = more swelling, logically... I don't know anything such as "over-hardening"; the excess will evaporate and poison your environment and that's all. (Again, logically.) If there's something particular about glut which I'm obviously ignorant about then disregard this post BTW, maybe the strength of your glut solution is weakened or they've sent you the wrong dilution by mistake!????

Regards,
Loris.

[donbga]

Less won't help I presume; since less hardener = less crosslinking = more swelling, logically... I don't know anything such as "over-hardening"; the excess will evaporate and poison your environment and that's all. (Again, logically.) If there's something particular about glut which I'm obviously ignorant about then disregard this post BTW, maybe the strength of your glut solution is weakened or they've sent you the wrong dilution by mistake!????

Regards,
Loris.

Based on Colin's numbers and the amount that I use, less glut will work unless there is another gremlin at work. The numbers for the glut dilution and rate of usage are directly in line with Chris Anderson's method of sizing with glut.

Glut used as a hardener is superior to Formalin or Glyoxal, IME. The hardened paper surface is very smooth and soft and the gelatin cures relatively rapidly (within hours) and resists staining.

You should try some.

[Colin Graham]

Less won't help I presume; since less hardener = less crosslinking = more swelling, logically... I don't know anything such as "over-hardening"; the excess will evaporate and poison your environment and that's all. (Again, logically.) If there's something particular about glut which I'm obviously ignorant about then disregard this post BTW, maybe the strength of your glut solution is weakened or they've sent you the wrong dilution by mistake!????

Regards,
Loris.

I came across this post (in this thread) from PE, which is what made me consider the possibility of over-hardening. It was made in reference to silver gelatin emulsions, so it might not apply to my situation.

But using more glut certainly didn't help- it seemed to progressively thicken even in a 45C bath and get a rich honey color that dried into a dirty yellow on the paper. Which still swelled up and got slimy in development. So less seems worth a try.

An overdose of hardener put into your emulsion can lead to a coating that is too soft. You have to have not more than 50% of the amount of hardener than can react fully with gelatin. If you go over that amount, it does not harden. Hardener is not washed out unless you process too soon, but in that case the emulsion will probably wash off as well.


PE

[Loris Medici]

Ok, thanks much for pointing that out.

FWIW, I personally use Formalin (37% Formaldehyde solution, a pretty old bottle nearing 3 years of storage my shelf now). I add about 1.5ml formalin (since I got the bottle fresh) into 100ml 3% gelatin (200 bloom) and it works like a charm - except for the odor when you size a relatively large batch; I simply close the door and come back to air the room when the coatings have dried... So, I'm with Kerik here.

[Loris Medici]

Oops! Missed that one...

Thanks for suggesting. I'm sure it's better somehow but I'm perfectly well with formalin, there's nothing I'd like (or can imagine!) to improve.

Formalin is very accessible to me (cheap and can purchase whenever and wherever I want - our rules are pretty relaxed here in Turkey...), OTOH, glutaraldehyde is a compound subject to special order.

Anyway, will have that on mind if I ever hit to a sizing related problem.

Regards,
Loris.

...

Glut used as a hardener is superior to Formalin or Glyoxal, IME. The hardened paper surface is very smooth and soft and the gelatin cures relatively rapidly (within hours) and resists staining.

You should try some.

[Katharine Thayer]

An interesting observation from PE that more hardening=a softer emulsion. Hard to know whether that's a relevant observation or not to our situation here. For what it's worth, I've not seen that with hardening gelatin for sizing.

I have seen overhardening of a colloid with a hardener, once, but that was when I was experimenting with using glyoxal to harden gum for a painting application, and tried several different strengths. The gum with too much glyoxal became very hard and crystalline on the surface when it dried, almost in texture as if it were coated with sugar or something. Again, not sure how relevant that is to the question here, just an observation.

[Colin Graham]

Thanks for sharing your thoughts Katharine. I'm probably reaching a bit with the overhardening angle, but it sounded good when I read it.

Anyway, I'm waiting for a paper order so I'll have to stew about it a little longer. I intended to wait to try the glut until after the paper showed up, but I figured what could go wrong?