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Autochrome / How to Remove Fixed Panchromatic Emulsion on Screen

Mustafa Umut Sarac

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Location
İstanbul
Format
35mm
I want to use exposed and fixed Autochrome plates in my photography after removing the panchromatic emulsion which coated on to lacquer and dyed starch grain layer without damaging the second and third layer.

George have unexposed Agfa Plates and he reported that if the plate put in to fixer without hardener , panchromatic layer peels off smoothly. I am in contact with him to obtain one or two plates but later I could buy Lumierre exposed ones and use them later also.

How to question is above.

Mustafa Umut Sarac
Istanbul
 
Is the varnisch water soluble if not maybe the emulsion layer is and you can remove the emulsion by soaking the plate for a prolonged time in destilled water.

Dominik
 
Hello Dominik,

I dont think that varnish layer could be influenced with weak chemicals , its job is to protect the screen from developer , fixer and water. But may be finding a faster method could protect the glass corner , screen corner gap between varnish corner from the moisture. Are you confident that only distilled water peels off the emulsion ?

Umut
 
Photo Engineer ,

Your answer would be great .

Thank you,

Umut
 
Heated water works faster, or you could use a hair dryer set to hot (around 60°C - 70°C max ) the heat should destroy the gelatine emulsion. I mentioned distilled water because of the effects of water impurities water stains etc.... Formamide also known as methanamide is a gelatin solvent but i don't know what effects it will have on the varnish. This link might be interesting to you: http://albumen.conservation-us.org/library/c20/kozlov1983.html

Good luck

Dominik
 
You could first develop the film to complete black and then use a copper-sulfate & hydrogen peroxide bleach. This will dissolve all the gelatin in contact with developed silver. This would be pretty damn easy methinks, as long as you have some kind of developer. In fact, if you used "Caffenol" or similar, you could probably get all of your materials at a grocery/pharmacy.

edit: It just occurred to me that this would only work for unprocessed plates. If you're using a pre-existing color image, then the bleach would in fact get rid of the silver areas, but it would presumably leave the silver-free areas with gelatin and the thickness would vary then.

Knowing what the varnish is made out of seems an important step. What about Shaz's (there was a url link here which no longer exists), or Bertrand's book; do either say?
 
Last edited by a moderator:
Chris ,

Thank you very much. I can find hydrogen peroxide but I am not sure for copper sulfate. I have D76. Can only HP works as a bleach ? How much water and HP necessary in the mix , mixing heat and bleaching time and temperature are also necessary.

Umut
 
Copper sulfate is used to destroy tree roots, so check at a hardware store. But for some reason, I found some at a pharmacy. No, HP alone won't do anything that I'm aware of.

Now remember, this is for an unexposed/unprocessed plate, but expose the hell out of it (i.e. take it outside and look at it for a long time in the bright sunshine... take your time). Then, develop it in D76 above 20° for any time greater than, let's say 10 minutes. This should definitely result in a black plate.

Technically the copper-sulfate/hydrogen-peroxide mixture is a bleach-etch. Here's a thread about it... (there was a url link here which no longer exists)

If you are serious, we can look harder for a formula. I'm just a little lazy at the moment...
 
An overnight bath in a mix Methanol 1:1 Aceton seems to be the norm these days to strip the emulsion from the film.

Dominik
 
Not to add too much confusion here, but if you are thinking about using old processed plates you may well have to remove a varnish layer to get to the emulsion. I believe it may have been common to coat the finished plate with a varnish to protect it. If the varnish layer is cracked (crazed) it may allow water to get to the emulsion and both layers lift off together. The Agfa instructions say to avoid an alcohol based coating and to use a Gum Dammar/Benzole varnish. This would indicate that the matrix is protected by a coating of shellac (one of the few finishes dissolved in alcohol). In fact I just made a trip to the basement and alcohol will weaken/remove the matrix protection. A thin film layer lifted off right away and the matrix layer could be removed by rubbing lightly with a brush. Once dry the color matrix that I didn't touch remained intact but very fragile when touched.
 
Thank you Chris, Dominik and George.

If I understand correctly there is a protector layer for panchromatic emulsion and under these two layers there is another protector layer for starch grains. If we dip everything to alcohol , there is a risk to damage the starch layer when removing top three layers. I wish top protector layer and bottom protector layer have different formulas.
May be top protector layer could be removed with matchsticks and cotton balls slowly with least alcohol inside.

May be top layer could also removed slowly with 2000 or more grade sanding paper
 
Only developed plates have a varnished emulsion unused plates don't. If they had the photographer wouldn't have been able to develop the plate.Even used plates were often not varnished. Beneath the emulsion layer you have a varnish layer don't remove it under any circumstances. The pigments that were used are water soluble. The Varnish that protects the starch/color is a mix between Dammar resin, ethyl acetate, nitrocellulose and castor oil.

Dominik
 
Thank you Dominik.

As George reported a alcohol soluble shellac varnish for panchromatic emulsion , you report a alcohol soluble shellac varnish for starch grains. Dipping to the alcohol destroys two of them and make the starch grains unprotected and fragile.

Lets continiue from here , what is the best way to remove the top of the all , shellac varnish without harming the other ?

Umut
 
Mustafa the top varnish was optional and in fact not done very often, when you get the plates the first thing you have to do is to check if the emulsion was in fact varnished. Use small amount of stripping solution on a cotton ball and rub it in the emuslsion or top layer don't use a bath.

Dominik
 
Dominik ,

Good advise on not using a bath. My sister is living at Paris and if I buy a plate , she would be the buyer. I think sending her to antique shops and giving time to study the art is only option.

Is there any online shop which sells unexposed plates ?

May be this is another thread subject.

Thank you ,

Umut
 
Dominik ,

You have reported that Autochrome plates have also a protective glass also , totally two glasses and a sandwich.
How to remove that protective glass ? Is it mobile or adhesived to emulsion shellac resin ?

Best ,

Umut
 
Mustafa the glassplates were glued together with an adhesive tape or paper strip. Simple cut trough the strip that's it.

Domink
 
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