Gelatin emulsion beginner
Few weeks ago I started my adventure with hand-made gelatin emulsion for glass plates. I found Mark Osterman recipe and guide. I followed it as firmly as I could but of course there were some small differences (mostly caused by lack of specific equipement, I also use food grade gelatin, not photographic grade - it's not easily accessible here sadly).
The results are somehow not satisfying and I cannot eliminate the problem that I'm having which is lifting off of the emulsion. 80 % of the plated I made has lifted off, it doesn't happen always the same way - sometimes it looks like the emulsion isnt "glued" to the surface if the plate at all and it just go off under water. Some other times it looks like the surface of the emulsion itself is melting and it's not smooth anymore, it has a wrinkled texture. There were also times that in the middle of the plate under the emulsion some kind of bubbles appeared and the emulsion started to lift from this spots on. Finally on a few plates the emulsion shrinked and after forming a web of ruptures also left off.
All those effects are happening on the same moment - after developping while washing and before fixing.
I tried several theories I came up with why it is happening. I ruled out bad developer, too hot temperature, bad water for washing (I tried with running and destilled water), different thickness of the emulsion, different methods of cooling emulsion after coating, lack of chrome alum (I made a 2% alum bath before and after developping). Nothing worked.
Then I found this forum and I thought maybe I'll try to ask for some advice here because now I'm seriously clueless. I hope you guys will help me out.
Thanks in advance (and sorry about not-so-good english),
Hi, Asarnil. Welcome to APUG and congratulations on your first emulsions.
You certainly have a can of puzzles. Hopefully, it's just one thing that needs changing. The most likely candidate is dirty glass. Getting your sheets really, really clean is key. I make a paste of liquid dishwashing detergent (one without any extra ingredients like dyes and perfumes) calcium carbonate and ethyl alcohol (Everclear or Vodka) and rub it around on the glass with a soft nail brush. Rinse first under running tap water; then in a bath of distilled water and alcohol. Air dry and never again touch the surface with bare fingers. You can also check your local stores for a powder (not paste) meant for cleaning fine glassware. I've used 'Barkeepers Friend' in a pinch.
Try clean glass before you make other changes. If that doesn't completely solve the problem, run up the concentration on your alum bath to 5%. I don't know if you are putting alum in the recipe finals, but I don't put hardener in my dry plate recipe and I don't seem to miss it.
Best of luck and fun,
Denise, thank you answering.
Even though I don't clean my plates as firmly as you, I used calcium carbonate (mixed with everclear alcohol and destilled water) on the first plates and only detergent (usual product to wash dishes) on the others. It doesn't seem to make any difference actually because the few plates that didn't come off were washed by either calcium carbonate or the detergent. Of course I'm trying to clean them as strictly as possible, I check for any stains or any dirt under bright light.
I don't add alum to the finals but I'm considering to add it just before coating.
Now I'm thinking that it all might be caused by my drying box that I made off a big carton box. The problem is there is absolutely no ventilation in it even though it's quite big. The plates lie down horizontally not vertically - don't know if it has any influence or not...
I look forward to any advices you can give me, I'm really clueless now.
Well, I would add that you should be using Chrome Alum as hardener in the emulsion at about 5 ml/100 ml of emulsion using a 10% solution. If that does not work, then soak your plates in 5% Chrome Alum just before development. Hold for 5 minutes, wash 5 minutes and then develop.
Plain Alum (the white powder) is not a good hardener. Chrome Alum (the purple powder) is a good hardener.
Great clue about the drying. It could very well be that your coatings aren't completely dry. Make sure to report back with the results of changing that variable .
PE: Typo alert: 5ml/100 ml will give you a 5% solution.
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I make a 10% solution of Chrome Alum in water and add 5 ml of this to 100 grams of emulsion which is about 10% gelatin, prior to coating. I hope this clarifies things.
Originally Posted by dwross
Thanks. I can see now what you meant in the previous post.
Originally Posted by Photo Engineer
I do think that's a bit too much hardener. Mark's recipe calls for 4ml of 5% chrome alum in his ~350 ml recipe. He cautions (and I agree) that too much hardener will prevent the processing chemistry from penetrating the dried emulsion. Hardener was originally added to dry plate emulsions as an 'insurance policy' against warm processing conditions, and Mark's recipe is true to its historical roots. With today's typical conditions of modern plumbing and easily-procured cold water, hardened emulsion is likely less of a necessity. I've never used chrome alum, but the couple of times I tried just a little glyoxal, the emulsion lifted off the plate in as pretty and perfect a sheet as you could ask for. Fine, maybe, for emulsion transfers, but definitely not the outcome I was hoping for . Mark's final advise on the subject is excellent: try different concentrations to find out what is best for your own circumstances.
Chrome Alum adheres to glass through a chemical reaction, or so I've been told. As such, the reaction is somewhat slow and the high concentration seems to work for me. I do agree though that tests are needed and time as well. Let the plates cure for a few days and they will be fine.
As for too much hardener, yes, you can lose speed and contrast so just develop longer! It will work. The great fear is having the emulsion harden before you coat it. That will happen at the wrong pH. Of course, it is just as frustrating to have the emulsion float off a plate. That means that it was hard enough but did not adhere properly to the plate for one reason or another.
Mark also suggests rasping the edges of the emulsion side of a plate before coating, using sand paper or a file, to roughen the edges of the plate. He finds that the emulsion will thus frill or loosen less and there will be less liftoff of the emulsion. I have tried it and found it to be a "maybe" not a definite "yes" as far as making an improvement goes. Of course, I have to try it more to gain a full feeling for any improvement.
Awe turning to ahh...
Well, not reeeeeally.
Originally Posted by dwross
People still have to "deal" with unfriendly environmental conditions at times.
I remember the fun of discovering that my work had bleached out compleately as it dried... I wanted to "optimize & minimize" so I had prepared a "virgin" emulsion with no additives... then I looked at the floor.
What an ugly little puddle that was.
Maybe 34+ C. that day.
But you are correct, it is possible to process and dry plates w/o any hardener, under ideal conditions.
Do you luckily have a "glass thumb"?
I suspect you must be "charmed" !
When it works, it works quite well.
but when it fails, it fails pretty good too!
WHAT is a soft nail brush?!!
Last edited by Ray Rogers; 06-27-2010 at 01:02 PM. Click to view previous post history.
Well, thank you all for the kind responses, I really appreciate it.
I just got back from my darkroom after using the last part of the emulsion I had. Finally I went with what PE suggested and added 1 ml of chrome alume to 20 ml of melted emulsion. I managed to coat 7 plates with it. The main difference between the plates I did before (with 80% of them lift off) and now is that they are drying now on the wooden rack (exatly the same Mark used in his guide) in a pretty big darkroom with much more air then inside a cartoon box. I strongly believe that it will do the trick (I really cross fingers on it as it will boost my motivation up finally).
Anywho, tomorrow I'll use and develop 3 of them and I'll keep you guys updated.
Oh, I thought I mention one more thing (Ray Rogers mentioned it also). It's scalding hot here right now and I think it might have some influence also. I even had an idea to put the plate in a fridge after exposing and before developping to make sure the air temparature doesn't melt it (I don't even know if it's possible). What do you think? Is it worth it? Or may it cause more bad than good.