View Full Version : Emulsion Stripping

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02-18-2012, 03:17 PM
Thank you, PE. I will look into those things. At least this time I could roll, fold, spindle and mutilate without the emulsion coming off the support while dry. That's an improvement.

Why would you suspect hardener, though? Can you explain to me the role that the hardener plays (or point me at a reference) in this process because apparently I do not understand. Obviously it does more than just make the gelatin harder.

No hardener or surfactant was included in the subbing and I don't believe there should be, right?

The hardener I am using is a 10% solution of chrome alum. 0.1 ml was added to 15 ml gelatin emulsion as well as 1 drop undiluted PhotoFlo as a surfactant. That was the level I settled on during my practice runs because a greater amount of alum (say 1 ml) was giving me a problem with the gelatin coagulating before I could spread it. Practice runs likewise used 15ml of gelatin. Coating temperature of the emulsion was 45C with the acetate/glass plate at about 38C. Processing was at 16C (room temperature of my workshop) in XTOL 1:1 for 6 minutes followed by 1 min 3% chrome alum hardening stop bath followed by Kodak rapid fixer where after 3 minutes the emulsion completely detached, but frilling started in the developer around the edges. The curing time was about 36 hours. Ambient temperature in the workshop is around 62F - about 40% rel humidity give or take a bit.

I cut up one of my practice runs from the other night and dropped a sample in distilled water and that gelatin is lifting in exactly the same way. Gelatin concentration in the practice runs is 8%, about the same as the emulsion. At least it looks like I don't have to use expensive emulsion to trouble shoot.

On a side note, would plain old Kodak powdered fixer be a better choice here than the C41 style rapid fixer? The C41 was sitting out on the bench so I just used it. I don't have any of the other mixed at the moment but I do have it on hand.

Sorry if this is a bit wordy - I am trying to describe exactly what I did. PE, your assistance and expertise is very much appreciated. Same goes for all the rest of you helping out.

-- Jason

Photo Engineer
02-18-2012, 04:07 PM
Well, to start with, I would use Kodak Hardening Fixer.

Now, hardeners:

Gelatin melts at about 68 degrees F (20 deg C) (Mees, Haist and Mees and James). Therefore your gelatin will swell and melt at virtually room temperature in water. A hardener will do 2 things. It will raise the melting point so that it will no longer melt and it will stick one layer to another. The former is cohesion and the latter is adhesion.

You need both.

Your hardener must be sufficient for both the layer you coat and anything underneath if there is no hardener in the underlying layers. Also the hardener must diffuse downwards and react. So, you need enough for the emulsion layer and the subbing layer, and you need time for it to move everywhere in the coating.

T&E, Trial and Error is often the only way to figure this out.


02-27-2012, 04:46 PM
Time to close out this thread for the time being. I can say that I have completely failed to sub cellulose diacetate. I've been through every formula that I could find here on APUG and patents and ... I've tried acetic acid based, ascorbic acid based, formulas dissolving CD in acetone to make resin to dissolve in the subbing, two step formulas, drying, not drying, whatever.

I can get the subbing to adhere to the base, soak it in water and it stays put. Coat same with gelatin and the gelatin binds to the subbing and pulls it off in water. Or the gelatin will just not adhere to the subbing. There have been various outcomes, but none have worked. Actually, my most successful test was just plain undiluted nail polish remover. That lasted for about two minutes before the gelatin started lifting.

I can successfully sub cellulose triacetate and soak it in water for over 10 minutes, but not diacetate. Only trouble is finding triacetate, other than dissolving emulsion off of junk film with bleach - which is my current source. If anyone knows of a source for triacetate, I'd like to know about it.

So unless anyone has some new ideas, I'm putting this to bed for awhile. Denise was gracious enough to send me some Melinex 535 and a 3M product, so I'm off in that direction with my DIY film making.

Interested in suggestions anyone might have but I am here to tell you all this is not easy. Or I've just missed the boat! :laugh:

Have fun, that's what it's all about!

Photo Engineer
02-27-2012, 06:38 PM
I have a suggestion that you may have already tried.

Get some of the Melenex support from the Formulary. Coat each side and see if what you are coating sticks to at least one side. This will tell us if your formula for coating is suitable. I know this can be coated, and one side gives results like you describe, but the other (subbed) side does not and makes excellent coatings.


02-28-2012, 09:26 AM
Hi PE et al,

I tried a piece of the Melinex 535 that Denise sent me. Was able to make a very nice, smooth coating with test gelatin. After letting it dry for about 3 hours by my portable heater, I soaked in room temperature water for 45 minutes (give or take a few) with no lifting, frilling or visible change. No green food coloring in the water.

Also coacted a piece of subbed and unsubbed 35mm triacetate (according to the datasheet) salvaged from an exposed piece of ORWO UN-54 after removing the emusion with bleach. Upon soaking in room temp water, the unsubbed piece lifted immediately, the subbed piece survived 15 minutes without incident, at least to my eye. This was using the acetic acid subbing from Kaszuba's patent.

I would say it's a combination of the diacetate material and the subbing folrmulas. Something in the gealtin coating step is preventing proper adhesion to the diacteate. As I mentioned above, subbing by itself (visible by red food coloring) seems to adhere OK. Once gelatin is applied it lifts within seconds. My only guess is that the chrome alum does not work as a hardener with the diacetate. When I get glyoxal some day I will try again.

Someday I will return to this, but for now I'm using the Melinex or 3M material, which also appears to perform as well as the Melinex.

Thanks for everyone's help. I've still got about 250ml of emulsion out of the original batch waiting to be coated and exposed!

-- Jason