View Full Version : Help with Hardener for Films and Frilling

07-01-2012, 01:35 PM
To all of our chemists and emulsion makers out there, as you might have read in some of the other postings, I have been trying to develop a method to coat emulsions on PET. Mostly it seems to work but I am trying to solve a problem regarding frilling at cut edges. In other words, everything is great until I try to slit the film sheet. Then I get frilling while processing. Frilling is worse in XTOL than plain water, so I believe that pH has something to do with this.

I believe I need to add a hardener, which I have resisted because of problems I've had with hardener and coating. Normally adding a drop or two of 10% Chrome alum turns the 10-20 ml emulsion I'm working with into glop in just a few seconds. So, obviously too strong. Trying to add very minute quantities gives not much or any effect. Done many a search through these archives and am now more confused yet! So I will put my question out there as a tongue-in-cheek textbook style question. :p These drive my kids nuts cause I do it to them in the car all the time.

Jason is working on coating 100 ml of an emulsion made with 8% gelatin on a 5 mil support. 5ml of 50% ethanol (aka vodka) has been added to the gelatin as a surfactant. He is having problems with frilling at cut edges when processing exposed film in XTOL. Jason has decided to try adding a hardener. He has chrome alum (CA) available. To add CA hardener to 100 ml of emulsion to be coated at 32.5 C,

A) Jason should mix a CA solution of what percentage?

B) How much of this solution should be added to the emulsion before coating?

So, no looking at your neighbor's paper. Pick up your pencils - - - begin! :p

Thanks for your help, Jason

07-02-2012, 04:26 PM
Jason, do you have Ron's book? I'd think that whatever percentage of CA is given for Mark Osterman's lantern slide formula would be a good place to start. I'd give it, but I don't have the book with me at the moment.

Is your emulsion in a hot water bath when you're adding the hardener? It seems quite incredible to me that it would harden up almost immediately unless it wasn't being heated to a proper degree. But then again, I'm just speculating.

Hardeners need time to work once coated; maybe even a day or two ideally. The lower percentages of chrome-alum will probably work, but give it enough time to work.

Could you give a more detailed outline of your exact procedure?

Best of luck!

07-02-2012, 05:19 PM
Oh, I somehow skipped this thread. Maybe I could copy what I already replied as a PM so that everyone can read it (there's nothing new here, but repeating things I've learned at APUG):

Indeed, I used glyoxal. I'm not sure whether I tried formalin too, but glyoxal has been my hardener of choice. As per PE's suggestion, I dilute the commercial 40% solution by 1+9 to 4%, and then use this at 5 ml per 100 grams of emulsion.

In the most successful PET coating, I had only minor frilling at cut edges - something less than 1mm frills.

I found that the sorbitol is almost a must, otherwise it is too "hard" and curls with incredible force. The sorbitol solved this problem like a magic. I can check the amount I used, I should have it somewhere down...

My ultimate recipe included one or two small drops [per 20 ml of emulsion] of Photo flo equivalent (I am using Agfa Agepon), the glyoxal and sorbitol.


I have to add that I add the hardener to a really warm emulsion. The emulsion is somewhere at about 40-42 deg C (105 F). And, stir/mix well!

07-03-2012, 11:17 AM
Last night I coated some more POG (Plain Old Gelatin) and used the CA hardener, both 3% and 10%. Worked fine. I must have done something wrong before, IDK. Maybe just basic panic. Now what I did do was to make sure that the gelatin was warmer AND constant stirring while adding the CA. Hrst, I used your numbers as starting points.

Thanks, Chris, I will look up the lantern slide formula if I can find it. I have not yet order my copy but hope to soon.

Next week I should have some glyoxal to try.

-- Jason

07-03-2012, 11:11 PM
I think the "glopping" problem has to do with using "recycled" emulsion vs a "first melt." Some times when doing coating tests I have taken stripped off emulsion, added some DW, allowed it to swell and remelted. Well, tonight that gave instant glop. Melted some new emulsion and no problems. IDK why this happens but seems to be the answer.

BTW, remelted emulsion seems to be OK for coating but it loses sensitivity.

Erythritol may be helping out with the adhesion and cut edge problem. That's what I was testing when I made the glop.

More to come.

Photo Engineer
07-03-2012, 11:21 PM

Try either glyoxal or chrome alum. Use a 10% solution (but with glyoxal which is 40%, it is 10%). Either one can be used, but chrome alum needs about 3x to 10x the time to harden. Also, use of a prehardener is indicated.


07-05-2012, 12:24 PM
Thanks, PE. I have some glyoxal coming in and am looking forward to trying that instead. But, what is a prehardener?

Here's something I found yesterday and was wondering if anyone could comment. I had two sheets coated with real emulsion using erythritol. The first had a little chrome alum added (5 drops 3% solution in 20 ml ethanol. This was added as surfactant / hardener 1 ml in 25ml emulsion). When the first coated sheet didn't glop, I added 2ml of the 10% chrome alum to the remaining ~12ml emulsion and coated the second sheet. (The second sheet didn't glop either) Now, on exposing a cut 120 size frame from each sheet, @ 1/8sec, f/5.6 dev in stock XTOL 5 min, the frame from the first sheet gave density about what I expected, but the frame from the second sheet was heavily fogged and maybe 1/4 the sensitivity. This was the from same melt of emulsion, just the CA was greatly increased in the second sheet.

Would Chrome Alum do that to the emulsion?

Regardless, I don't believe that much hardener as in the second sheet is needed. Adding erythritol at 5% (v/v) rate to the emulsion has seemed to cure the frilling problem. I made 4 negatives yesterday, all from cut pieces, with no frilling at all. My erythritol was a ~70% solution, 35 grams (and change) in 50ml DW. IDK if this much erythritol is needed - maybe less would do.

If I can figure out how to scan a 6x9 negative, I will post some. I did one 35mm and maybe will get some time to post that this evening.

-- Jason

PS: XTOL seems to not be a great developer choice. Maybe need a more "historical" developer. Fog is also slowly increasing in my emulsion because it's getting pretty old now.

Photo Engineer
07-05-2012, 12:51 PM
I would suggest trying D76 or Dektol for this emulsion. IDK which would be better, but I think that one of them would be better than XTOL.

In my post above, there is an error. I should have said that commercial Glyoxal is 40% and I dilute it to 10% which is thus 4% Glyoxal.

And, NO, chrome alum is not known as a fogging agent. However, heat is. Maybe keeping the emulsion melted a long time under a safelight did the trick.

A prehardener is used before the developer. I use either formalin or chrome alum.

Formalin prehardener.

Water 800 ml
Sodium Sulfate 50 - 100 g
Formalin 10 ml
water to 1 L
pH 10.0 or same as developer

Process cycle.

Preharden 1 - 3'
wash 2 - 5'
Run regular process cycle!