Odd Gum Bichromate Problem

[Jon Harwood]

I ran into a curious Gum problem. I am a new gum printer, so this may seem basic to more experienced folks.

Recently I switched my sizing formula from hardening with Glyoxal to Glutaraldehyde. My sizing problems were resolved by the change. At the same time, my old supply of gum ran out and I opened a new container (from Photographer's Formulary).

Suddenly I observed an increase in required exposure of about 3x (1.5 stops).

Since I changed two variables at the same time I am uncertain about the cause of the sudden increase in required exposure. I doubt it was the change in my sizing formula and I suspect that the change from "old gum" to "new gum" is the culprit.

Has anyone else experienced this kind of change and does anyone have any idea what may have caused it? I would appreciate any insight.

 

[Lukas Werth]

First, just as a matter of interest, allow me to ask how you came about this new formular. I have not heard of Glutaraldehyde as a hardening agent. I have just read in Wikipedia, however, that it has very irritating smells. So, what is the advantage over glyoxal? Could you tell the dilution you use?
Regarding your question, I would guess otherwise, and suspect the new hardening method as the culprit - even though, given the many variables in direct pigment processes, it is hard to tell.
Do you add the hardening agent to the gelatine when sizing the paper or do you harden in an extra step? Do you wash the paper after hardening? If not, I suspect there might lie the problem.

 

[Loris Medici]

I remember reading somewhere that the acidity of your gum solution affects printing speed e.g. high pH (more alkaline) -> slow speed, low pH (more acid) -> high speed. (AFAIK, this is also observed in carbon printing when using dichromate sensitizers with different pH levels...) So, if everything else was kept constant, I'd suspect that the cause is different pH of new gum and/or different pH of the new hardening solution (affecting the surface pH level after application). But that's just an educated guess -> never experienced something like that!

Regards,
Loris.

 

[Kerik]

Glutaraldehyde as a gelatin hardener has been discussed in depth on the alt-process email list. Many people seem to like it, but it didn't work well for me. I prefer Formaldehyde.

 

[Jon Harwood]

I was having minor staining problems with Glyoxal so I wound up double coating the gelatin, that lead to coating issues "fisheyes" in the sensitized emulsion. So I gave Glutaraldehyde a try based on Christina Z. Anderson's book. Glutaraldehyde is a cousin of formaldehyde and probably just as toxic, so extra precautions are required. I size in small batches, currently 5 9x12 sheets for 8x10 printing. For that I mix 50 ml. distilled water, 1.3 g. gelatin and 0.3 ml. of 2.5% glutaraldehyde. With this mix the "fisheyes" can be easily eliminated while brushing on the emulsion and single coating works. I would guess all of this relates to the eccentricities of my location and workflow and I think glyoxal is a good hardening agent. It is said that some have an issue with glyoxal yellowing but I have not experienced it. Glutaraldehyde is a newcomer to gum printing but reportedly has a good history as a gelatin hardener for silverprints and is apparently used by those who make their own printing emulsions.

I mix the hardener into the warm gelatin just prior to coating. I have not washed after hardening and I appreciate the suggestion. If I have more issues I will add a washing step after sizing.

It could well be the glutaraldehyde that is changing the exposure times. I really don't know. Fortunately is is a managable problem.

Thanks Again!

jh

First, just as a matter of interest, allow me to ask how you came about this new formular. I have not heard of Glutaraldehyde as a hardening agent. I have just read in Wikipedia, however, that it has very irritating smells. So, what is the advantage over glyoxal? Could you tell the dilution you use?
Regarding your question, I would guess otherwise, and suspect the new hardening method as the culprit - even though, given the many variables in direct pigment processes, it is hard to tell.
Do you add the hardening agent to the gelatine when sizing the paper or do you harden in an extra step? Do you wash the paper after hardening? If not, I suspect there might lie the problem.

 

[Jon Harwood]

That is a good guess I think. I may have gotten a big increase in required exposure from both the hardener and the gum contributing to the situation. I was surprised, but I should know by now that gum has its surprises.

Thanks,

jh

I remember reading somewhere that the acidity of your gum solution affects printing speed e.g. high pH (more alkaline) -> slow speed, low pH (more acid) -> high speed. (AFAIK, this is also observed in carbon printing when using dichromate sensitizers with different pH levels...) So, if everything else was kept constant, I'd suspect that the cause is different pH of new gum and/or different pH of the new hardening solution (affecting the surface pH level after application). But that's just an educated guess -> never experienced something like that!

Regards,
Loris.

 

[Jon Harwood]

I imagine formaldehyde does just fine as well as repelling any bugs interested in dining on one's prints.

Thanks,

jh

Glutaraldehyde as a gelatin hardener has been discussed in depth on the alt-process email list. Many people seem to like it, but it didn't work well for me. I prefer Formaldehyde.

 

[Lukas Werth]

I think Loris' guess may actually be the right one. I misread your, Jon's, first message - with hardener problems, exposure times should go down, not up, and there shuld be problems with clearing. (on the other hand, casein is very alkaline, as it is dissolved in ammonia, and gives me consistently shorter exposure times than gum).
I have never experienced "fisheyes", don't even know exactly what this means - bubbles in the dichromate mix?
Also, I have only ever used glyoxal. Paper does develop an orange stain if it is kept for some time after sizing/hardening, and if it is not washed after the hardening step.
For this reason, and because sizing mistakes can be corrected, and also because dissolved gelatine may be ket in a fridge, I brush on gelatine first on dry paper, dry, and then apply the glyoxal solution with a foam brush, dry, wash. I find this little extra work, and I don't get orange stains even if I keep the paper. Also, I size full sheets and cut them to size later.

 

[Loris Medici]

Lukas, casein (proteins) and gum (polysaccharides) are quite different and may behave pretty differently -> so that would be comparing apples to oranges.
BTW, I have 2kg's of Kremer Casein that I would like to make use of. What would be your suggestions to me for dissolving the casein? (I have concentrated ammonia; how much casein in how much water and how much ammonia for a neatly working coating solution? How much dichromate; strenght, casein+dichromate ratio?... How do you develop your caseins? Just simple automatic development or by manipulation?)

Thanks in advance,
Loris.

P.S. (Have you had to look for the type/brand of the varnish BTW?)

 

[Jon Harwood]

Hi Lukas, Thanks for the clarification. I will assume the new batch of gum is most likely responsible for the change.

"Fisheyes" are small areas (2-3mm) where the emulsion draws back creating a hole in the coating. This could be caused by excessive thickness gelatin in the sizing. I usually see it in the red layer of a tricolor, possibly because my red is an earth color and the other two are not.

jh

 

[Loris Medici]

Jon, could be the glutaraldehyde as well -> if that's Ryuji's stuff, there should be a weak alkaline buffer in it (for preservation)... (IIRC!) But, on the other hand, since the hardener's alkalinity is weak and it's used in very small amounts, probably it's more about the gum - as you assume. (Gum can be very different batch to batch / supplier to supplier...)

... I will assume the new batch of gum is most likely responsible for the change ...

 

[Lukas Werth]

Jon,
yes, I know them (fisheyes). Had them also, but so far I have always been able to finally coat such areas.
Loris, 10cc household ammonia (9%) for 0.8g casein is my ratio. 12-30 drops for an 8x10, depending on paper, contrast, pigment, and so on, about 1.5cc dichromate (I mostly use 6% or 10% potassium, ammonium for soft contrast, sodium for some reason I have so far mostly used for gum), and I regularly regularly give a first coat of only casein and water (15-25 drops for an 8x10).
The casein image is more stable than gum, I most of the time end up developing some areas by dropping water on then, only rarely brush for small detail. A disadvantage is that the casein image stops dissolving/developing after some time, so your exposure needs to be more on the spot.

 

[Loris Medici]

Thanks Lukas.

I tried with 25% ammonia (d=0.91g/ml): 1.6g casein + 10ml water + 12 drops of ammonia (~0.5ml) + water to make 20ml + 2ml isopropanol (to eliminate bubbles) gave me a pretty homogeneous solution. The amnt. of ammonia I used was approximately 0.0625g per 0.8g casein; that is ~14-15 times weaker than your formula! Should I definitely add that much ammonia? (Or, the criterion is to have a homogeneous "solution"?) Is there a strict/dictated amnt. of ammonia?

Thanks again,
Loris.

 

[Lukas Werth]

Thanks Lukas.
....Is there a strict/dictated amnt. of ammonia?

Thanks again,
Loris.

Not at all, or not that I would know. I arrived at my ratio entirely through trial and error. It has a strong smell of ammonia (the dichromate turns yellow), but I can dissolve the ammonia quickly in this way. I find this wishful because the solution, as far as my trials go, has very poor keeping qualities, even in a fridge. I make only 10-20cc at a time, depending on my need, and use it within 24 hours.
I have kept the ratio simply because in this way I get a handle on how many drops of casein solution I need for a given coating.

 

[Katharine Thayer]

A different voice

Jon, I'm curious how much time elapsed between printing on glyoxal with the old gum and printing on glutaraldehyde with the new gum, and whether the seasons/weather changed between. My own experience/observations don't support the idea that either gelatin hardeners or different gum brands could make that much difference in speed. A difference, sure, but when I tested six different gums, the biggest differences between them were more like an exposure increase of 1/3 or 1/4 (in other words, an extra minute on an average 3 or 4 minute exposure) nothing like one gum needing 3x the exposure of another, so I am inclined to be very skeptical about this explanation. And by the same token, I've seen similar small variations in speed between different sizings, but not huge variations like this. But, I have seen, routinely, huge differences in speed when seasons change, particularly when there's a marked change in ambient humidity, so that's my first thought. Often it's not the obvious culprit, but something else, that's causing an effect.

BTW, I would caution anyone thinking of using glutaraldehyde to be sure to buy only the very dilute solutions now available from some supply houses especially for this purpose (like Bostick and Sullivan or Photographers' Formulary). Under NO circumstances should you buy it from a chemical house and dilute it down yourself, unless you have access to a lab with a vented hood. I started with 8% and breathed too much of it while diluting it, even though taking care that there was good air circulation, with rather disastrous results.

Katharine

 

[Jon Harwood]

Hi Katharine,

It has been a very odd occurance. The time elapsed between glyoxal sized paper and glutaraldehyde sized paper was one day. Prior to printing I test the humidity with a sling psychrometer and there was no change beyond the 10% range. Temperature and weather were similar.

However I had recently been bedeviled with a series of difficulties. First, about a week before switching sizing I was confronted with severe fisheyes on the second tricolor coat. I attenuated this problem by pre humidifying the paper prior to coating. ***This pre-humidification may have reduced the exposure times.*** The pre-humidification helped with the fisheyes, but then I got a staining problem, so I double coated some paper using glyoxal and was able to print, I also continued to pre humidify the paper before coating. The double coated paper still had a stubborn problem with fisheyes even though I could brush them out when the paper was pre humidified .

Then the glutaraldehyde arrived from photographer's formulary and I single coated some paper with it. Simultaneously my gum supply from photographer's formulary kits ran out and I opened a new 1/2 gallon bottle of photographer's formulary gum. I printed with the new gum, the new sizing and I did not pre-humidify the paper (I had forgotten to say I was not pre humidifying the glutaraldahyce sized paper in the earlier post) This was the point at which the required exposure seemed to triple. The fisheyes were much less of a problem and I could brush them out during coating. As I have continued printing with the new sizing I am also thinking the increase in exposure may have only been a factor of two (one stop) not three.

At present I think the increase in exposure may have been caused by mostly by switching away from pre humidified paper and possibly by getting a different batch of gum that may be either younger or older than the prior batch. The change in sizing may have also contributed but I think the most important thing could be discontinuing the pre humidification step.

What ever the cause it has been one in a series of strange problems I have had to figure out. I have found myself quite totally hooked by gum even though it seems to be doing anything and everything it can to convince me that it is impossible to handle. After the last batch of challenges I seem to have arrived at a workflow that is producing one or two steps of extra contrast and which holds out hope of making a tricolor in three steps rather than five or six, so it has probably been worth it.

BTW I am very paranoid about glutaraldehyde. I handle it as if it was formaldehyde using particular caution when diluting it from 24% to 02.4% in a well ventilated area. I do not appear to be sensitive to it under the conditions I used it.

Thanks for the advice and analysis it reminded me of what may well have been the decisive factor.

jh

Jon, I'm curious how much time elapsed between printing on glyoxal with the old gum and printing on glutaraldehyde with the new gum, and whether the seasons/weather changed between. My own experience/observations don't support the idea that either gelatin hardeners or different gum brands could make that much difference in speed. A difference, sure, but when I tested six different gums, the biggest differences between them were more like an exposure increase of 1/3 or 1/4 (in other words, an extra minute on an average 3 or 4 minute exposure) nothing like one gum needing 3x the exposure of another, so I am inclined to be very skeptical about this explanation. And by the same token, I've seen similar small variations in speed between different sizings, but not huge variations like this. But, I have seen, routinely, huge differences in speed when seasons change, particularly when there's a marked change in ambient humidity, so that's my first thought. Often it's not the obvious culprit, but something else, that's causing an effect.

BTW, I would caution anyone thinking of using glutaraldehyde to be sure to buy only the very dilute solutions now available from some supply houses especially for this purpose (like Bostick and Sullivan or Photographers' Formulary). Under NO circumstances should you buy it from a chemical house and dilute it down yourself, unless you have access to a lab with a vented hood. I started with 8% and breathed too much of it while diluting it, even though taking care that there was good air circulation, with rather disastrous results.

Katharine

 

[Lukas Werth]

Katharine,
regarding the problems of glutaraldehyde you mention, I am curious about its advantages. Do you think it is better than glyoxal (or,l for that matter, formaldehyd), and, if yes, why?
Also, can it be brushed on in an extra step? This is what I usually do with my glyoxal.

 

[Loris Medici]

Jon, that's a serious change in the workflow! In the light of this, I'd pass the theory (which was based on the assumption that everything else was kept constant - as I stated before) about alkaline sizing and/or alkaline (or - more likely - less acidic) gum. As Katharine says, humidity has a lot (LOT!) effect on printing speed, so, now I think *not pre-humidifying the paper anymore* is the actual/real reason of your speed decrease. (BTW, pre-humidification is my standard practice. I use a ultrasonic humidifier now, was using near boiling temperature hot water before...)

BTW, sometimes bits and pieces of pigment/dirt (small protrusions on the print's surface) and whatnot will cause small fisheyes that are almost impossible to fix. Moreso with some pigments; I have this phenomenon more often with PV19 Rose for instance. Try to keep your developing water clean and clean your prints from bits and pieces. (Such as not well dissolved pigment particles, hair...) Also try harder to size evenly; uneven and excessive sizing may cause fisheyes too.

Regards,
Loris.

...I did not pre-humidify the paper (I had forgotten to say I was not pre humidifying the glutaraldahyce sized paper in the earlier post)...

 

[Katharine Thayer]

Katharine,
regarding the problems of glutaraldehyde you mention, I am curious about its advantages. Do you think it is better than glyoxal (or,l for that matter, formaldehyd), and, if yes, why?
Also, can it be brushed on in an extra step? This is what I usually do with my glyoxal.

Lukas, I don't personally see any particular advantage to glutaraldehyde, and I don't think glutaraldehyde is better than glyoxal, which is my preferred hardening method. I didn't test the glutaraldehyde extensively because of the issues I had with the fumes, but the tests I did run showed no advantage for the glutaraldehyde. I don't seem to have on my site a comparison of printing gum on glyoxal vs glutaraldehyde, but I do have a comparison of glutaraldehyde vs printing on unsized paper, where I preferred the result on the unsized paper to the result on the glutaraldehyde-sized paper. If you're interested in that comparison, go to my page on sizing and scroll down to the first set of pictures you come to, and its accompanying text:

http://www.pacifier.com/~kthayer/html/size.html

You'd have to ask someone else the question about brushing it on separately.
Katharine

 

[Lukas Werth]

Thank you, Katharine, this is exactly what I wanted to know. I will stick with my glyoxal then. By the way, just to let you know, when I harden by brushing on the Glyoxal later, I dilute it further, adding about 3cc of glyoxal to 50cc of water.

 

[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.