Gelatin Questions

Photo Engineer

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Ned, thanks. I try to help.

Now, let me clarify something. Undissolved gelatin in a solution of gelatin is called a slug. They cause problems throughout the process they are found in.

Gelatin that is solid comes as granules or sheets. We used both at EK. They are both "bloomed" in water by using gentle heat and at this time the granules go from that form to either a solution or they do not go into solution. If they do not, they just swell up and become slugs which are translucent things shaped like garden slugs.

I have opened jars of many powdered chemicals and found evidence of static electricity. One jar literally "exploded" with powder spraying my work area with dust from the jar. Small particles climbed up the sides and over the edge of the jar as if they were alive. I put the lid on and had to clean up the area. Then I wet the areas down well and washed the bottle and tried again. The higher humidity seemed to have worked.

PE
 
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NedL

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Got it Everything I mentioned above about static was dry granules. My original problem was dry granules getting into the solution just prior to coating, without enough time to dissolve. Being more careful has solved the problem and all is well, but filtering like you and Vaughn suggested probably would have solved it as well. I'm sure the slugs will cause me trouble some other day. They sure cause trouble with my garden peas and lettuce.

Photo Engineer said:
... Small particles climbed up the sides and over the edge of the jar as if they were alive.
PE
Click to expand...

I have no trouble at all believing this after what I saw last night. I was amazed how much motion there was in the granules.

HNY everyone.
 

Vaughn

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As an aside, I normally use food grade gelatin which is made up of very fine granules. Most of the old carbon printing manuals recommend a 30-minute wait while the gelatin absorbs the water before one melts it. I still do, but I find the small grains of the food-grade gelatin become a complete gel within a couple minutes (which is why I stir it quickly!)

I have a box of photo-grade gelatin that looks more like the shape of rabbit food, which does take the full 30 minutes to absorb the water. The water is usually tap water, <70F, but greater than 55F, depending on the time of year.
 

Photo Engineer

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There are additives in food grade gelatin that are both on the box and not listed due to being below reporting limits.

This includes silica gel to help keep it dry and some sugars to help when it sets up. (IIRC).

PE
 

Vaughn

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Any possible additives to Knox or bulk gelatin have caused absolutely no problems with carbon printing -- silver emulsions could obviously be a different story. I have seen nor experienced any differences in handleing or results from 50% food grade plus 50% photo grade vs 100% food grade in making gelatin prints. Any modern gelatin is probably much cleaner/purer than any gelatin used when carbon printing was patented. Fortunately it is not rocket science -- closer to cooking! And chefs can be more particular than photographers about ingredients!

FWIW...No box of food grade gelatin I have seen (actually I have seen only three manufactures' boxes, so it is a limited sample, but includes Knox) has ever had any other ingredient listed other then gelatin. The package of bulk gelatin I have (from Bulk Foods) hails from Argentina and on the label says "Ingredients: Unflavored Gelatin. Simply gelatin with no fillers or additives of any kind."

There is a food grade gelatin I might try someday -- no color tint to it and forms a perfectly clear gel. It is popular amongst those coating watercolor paper to receive a carbon transfer, as it does not give the paper a yellowish cast as regular food grade can.
 
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NedL

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The ossein photo-grade gelatin I'm using has a slight yellowish cast. I'd be interested in trying one that is perfectly colorless. I think for what I'm doing now, it is important for it to be fairly hard, but for uses like sizing a water-clear gelatin would be nice. I've been thinking of coating the whole sheet of paper so that the edge of the gelatin layer is not so evident. I'd also be interested in learning how to make the surface less shiny... was thinking of adding a starch of some kind...
 
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NedL

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Now that you mention it, I've only noticed the slight yellow cast while it is drying. I don't recall noticing it on the finished, dried print. I'll look at them more carefully. The starch will wait until everything else is under much better control, and I'm still a long way from that.
 

Vaughn

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I have not prepped watercolor paper with gelatin, so the only info I have is from other carbon printers who have experimented and otherwise worked with coating papers with non-pigmented gelatin. Generally they have noticed the slight yellow of the gelatin on the white of the watercolor paper when dry. I have not made a batch of gelatin with just photo-grade, so I have not been able to compare it with the food grade I use.

The gelatin used to avoid the yellow is a special bakers gelatin for making perfectly clear candies and such. I suppose that there are no impurities in that stuff. I do not have the name or source available.
 

Andrew O'Neill

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I have sized papers with 5% gelatin (for carbon transfer), hardened with Ammonium Dichromate and UV light, and didn't see yellowing. At 8% gelatin, I did, however. The addition of starch cuts down on the shine.
 

Vaughn

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Thanks, Andrew...I failed to consider gelatin concentration as a big factor.
 

Photo Engineer

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Gelatin concentration is actually not the figure to use. You should use the actual laydown in mg/m sq or mg/ft sq.

PE
 

Vaughn

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Photo Engineer said:
Gelatin concentration is actually not the figure to use. You should use the actual laydown in mg/m sq or mg/ft sq.

PE
Click to expand...

That makes sense. I lay down my glop (pigmented gelatin w/ sugar and a little alcohol) at the rate of 1.2 ml/in sq. Might be a little on the thick side, but it pours easily, smoothly, and the tissue is easy to work with. I pour about 290ml on a sheet of fixed-out x-ray film (14"x17") and spread it out with my fingers. Lots of fun!

Coatings on watercolor papers as a sizing tend to be thin -- so gelatin concentration (and the amount of color native to the gelatin used) in this case becomes a big factor.
 

Tom Taylor

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Good idea Ned. I'll probably order a box or two as well. For other ideas google Antistatic Towelettes. - e.g., http://www.americancleanstat.com/wiper-staticide-towelettes.html Ohaus includes "Antistatic Towelettes" with the CT200 balance. For small amounts of chemistry I measure in plastic salsa condiment cups that you can get for free on your next visit to a Mexican fast food restaurant. If all the grains don't fall into the solution, you can tap the backside with the stirrer until they do or put a drop or two of the solution into the cup to dissolve the remaining particles and then add to the rest of the solution. The real problem arises when you need to measure out a larger quantity and need to use the scoop. This is when having a scoop that has been treated to eliminate the static charge comes in handy. Alternatively, I imagine, you could measure the chemistry directly into the mixing beaker to guarantee that all that's supposed to be in there is in fact in there.

Thomas
 

pschwart

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water white gelatin: try SuperClear from custom Collagen at http://shop.customcollagen.com

If you want to check for a yellow cast:

Mix the same gelatin at various concentrations, say 3%, 6%, 9%, or whatever tickles your fancy. I did this some years back, mixing 20 ml gelatin in a 30 ml plastic beaker made for mixing expoxy. Let the gelatin gel completely and compare. Most food grade gelatins will have a yellow cast that increases with the concentration. Yes, the cast will also increase with the coating depth. That's another simple test

BulkFoods gelatin at 5%-6% won't be discernably yellow on most watercolor papers in thin coatings applied with a pad or 95 rod.For thicker sizing or bright white supports, there is always SuperClear.
 
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NedL

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That's pretty funny Thomas! I do exactly the same thing... I even know which Mexican restaurants have the best hydrophobic condiment cups that are the perfect size for my hake brush! For my recent experiments, I've just been measuring directly into plastic film canisters and using the tare weight for gelatin, AFC and water.

The static problem I had a few minutes ago was just ridiculous. Some dog hairs and lint were on a sheet of rubylith. When I went to wipe the rubylith with a clean cotton rag, the whole sheet moved away from the cloth. I couldn't get the cloth to touch the surface and I didn't want to set the rubylith down anywhere for fear it would pick up even more lint and hair. Finally I folded the rag and pulled the rubylith through it, but I didn't get them all... the fine hairs would move an inch or two on the surface of the rubylith but they were really stuck on there. I'm ordering kimwipes or some kind of anti-static towelettes tonight!
 
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NedL

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pschwart said:
water white gelatin: try SuperClear from custom Collagen at http://shop.customcollagen.com
Click to expand...

I got a kick out of reading the FAQ at that site. The superclear is 300 bloom gelatin made from pork skin ( look in the "documentation" section under "pork skin" to find the specs for superclear). Thanks, very interesting!

Okay: I couldn't resist. 2 pounds of superclear are on the way here. I'm playing with something similar to Halvor Bjoerngaard's "Chiba stystem" and he wrote that pig skin gelatin worked better than ossein, so it's probably worth a try for me.

Thanks for the tip!
 
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Photo Engineer

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It is unknown if the gelatin at your reference is inactive or active gelatin. If it is active, it should not be used in silver halide photography unless you have more information.

As for your test, it is not reliable. If you compare the 3% vs the 9%, you will find that you need 3X more of the 3% to get the same effect, thus giving the same "yellowness" of the 9%. In other words, if you lay down 500 mg/ft sq, they you will have to use different amounts of each solution but the final result will be identical in mg / ft sq, ft.

PE
 
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NedL

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PE thanks for the warning, that's important to keep in mind. Two more questions if you don't mind!

1) if the gelatin is active, what would go wrong? Would it be possible to tell by the problems encountered?

2) Here's the information from the specs for that "SuperClear", can you tell if it's active from this?:

GELATIN - 300 BLOOM - PORK-SKIN Description:

Dry granules with 99% passing through a #40mesh U.S. standard sieve. A purified/sterilized collagen extracted from pigskin.


  • Gel Strength: 300 +/- 10 bloom
  • Viscosity: 53.0 +/- 8.0 mps
  • pH: 4.80 +/- 0.60
  • Ash: 1.0% maximum
  • Moisture: 12.0% maximum
  • Odor & Flavor: No objectionable odor or flavor
  • Solubility: Soluble in hot water Insoluble in cold water

Then it lists some microbiology with minimuim E. coli and salmonella negative.
 

pschwart

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My test is absolutely reliable for sizing papers where one might vary the gelatin concentration specifically to get a *different* effect (as in sizing carbon supports). Sorry if I drifted off topic.
 

Photo Engineer

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pschwart said:
My test is absolutely reliable for sizing papers where one might vary the gelatin concentration specifically to get a *different* effect (as in sizing carbon supports). Sorry if I drifted off topic.
Click to expand...

Well, IDK, it is not for Silver gelatin!

PE
 

Photo Engineer

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OK, gelatin activity is not important in non Silver processes. There, that dispels one proble.

However, tuberculin content is a mandatory reporting item in the USA. IDK about elsewhere.

Pig gelatin has minimum swell at ~pH 9 while bone gelatin has minimum swell at ~pH 4.5. If this feature is important to you then you should be aware of it and its implications.

PE
 
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NedL

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The only other microbiology report was a "total plate count", which I guess would be a visual count of bacteria colonies. IDK if that test covers tuberculin bacteria, but it doesn't sound very specific.

Thank you for the information about swelling. I need to go read and learn more about this, it looks important to understand. It could possibly explain something I saw just this afternoon: I used a little citric acid in the wash and then thought the gelatin had less relief than I expected. Perhaps I suppressed the relief by lowering the pH. Lots to think about here.

One more thought: I've been reading a lot about bromoil and oil prints in the past month. Many hundreds of pages and descriptions and articles. It strikes me that I've seen no mention of the type of gelatin at all, but that I've seen contradictory information about pH and inking. The first paragraph of this article is only one example. It might be simply explained if Hewitt in 1908 was using pig gelatin and Ed Buffaloe was using ossein. It's probably more complicated than that, but it seems like a big important variable is never even discussed! Very interesting.
 
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Andrew O'Neill

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I found some info on the net about reducing slugs... perhaps PE can verify this:

"Dissolving was achieved by a cold soak at 4° C. for 30 minutes followed by heating at 50° C. for 45 minutes. The dramatic decrease in gel slugs..."
 
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