View Full Version : Substrates for Shooting in Camera - FILM, Acetate, PET (polyester), Glass, etc.

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07-20-2012, 10:39 AM
Jason, those are fantastic test ideas; thank you very much!

Here's the test from patent 2,014,547:

The stripping test usually comprises two parts, namely, dry stripping and wet stripping. The wet stripping test is carried out as follows: A strip of the emulsion coated film of convenient size, say 6 to 40 inches, is soaked in water at 70°F for ten minutes. It is then removed from the water and fixed on a flat surface with the emulsion side up. The emulsion is then gouged or creased with the finger nails at points near the middle and end of the strip. Each nail scratch tears the emulsion away from the support to a certain extent. The scratched places are then rubbed with considerable force with the balls of the finger tips for several seconds. A film is said to have satisfactory wet stripping (emulsion adherence) properties when no peeling, or substantially no peeling, of the emulsion occurs as a result of this rubbing action. Wet stripping is said to be unsatisfactory when an appreciable or large amount of the emulsion comes off. For most types of film it should not be possible thus to remove pieces wider than 1/4 inch by this test.

Is the terphthalic acid coming from the PET and "poisoning" your NaOH subbing bath? What about the ethylene glycol, where does that come from? It's a very clever theory, and seems like a good explanation if you're discovering that the peeling sheets are those which were treated in this potentially compromised bath.

Unfortunately my coatings have no hardener in them, so I might have to harden them or lower the temp° of any wet tests.

07-20-2012, 10:46 PM

The PET, or poly(ethylene) terepthalate, is made by the estrification terepthalic acid ethylene gylcol. By soaking the PET in the NaOH solution with some heat, the PET is subjected to saponification (base hydrolysis of an ester) which breaks the PET down into the salt of the carboxylic acid (terepthalic acid) and the alcohol (ethylene glycol) that formed it.

Terepthalic acid is a colorless solid with very low solubility in water, so it makes sense that it would have settled out. Ethylene glycol is miscible in water, so it's in solution. Because of the hydrolysis the solution starts going bad from the moment you start using it. However, hardware store lye is cheap. And I suppose it cleans out your drain somewhat when you dump it.

I'm on the edge of my chemistry so if I have this all wrong, please jump in and correct me. Anyway, unfortunately I did not check the pH of the 1M NaOH solution before I started. So maybe it's the acid, or the ethylene glycol, or my solution is defective, not really sure.

At the moment, I am fooling with an alternative process that looks even more promising. Or it might be a bust!

More to come.

-- Jason

07-20-2012, 10:56 PM
Even on cut edges and without sorbitol, there appears to be no signs of delamination or peeling. I'm skeptical... I think it's a trick.. as soon as I coat something important, it will peel!

Chris, put it through some developer and see what happens. The Melinex 535 and the 3M product do not seem to require any sugar alcohol or hardener. IDK if it would work better with those additives.

On another note, the other night I processed some Tri-X in the same plastic tub I used for washing the NaOH treated PET. This was a mistake! PE told me that NaOH was a foggant and I believe that some residual NaOH in the tub got into the water and messed up the Tri-X. Now I haven't used Tri-X in a long time and never in 120, but I don't remember it having a purple frosted base. Fortunately the negs are not important and look usable but word of caution, the NaOH seems t work itself into some plastics and is a b%&$h to get out!

-- Jason

Photo Engineer
07-21-2012, 10:28 AM

You have the saponification correct above. However, some of the PET will be partially saponified and the phthalic acid in this case will be attached on one side to the ethylene glycol and the other end will be free to grab gelatin. This is a very efficient way to create the adhesion we want. OTOH, you have to remember that in all of these methods a thin layer of PET is destroyed. The choice then is to choose the least harmful method.

In the case of NaOH, didn't you mean NH4OH? Sodium Hydroxide in excess will cause extremely rapid development that leads to fog, but alone it does not cause fog. In fact, I doubt if there was enough residue in your tub to cause any problem at all. NaOH washes out very rapidly and completely with just several changes of water.


07-22-2012, 12:55 PM

Thank you for the "heads-up!" to avoid using the same plastic containers to both sub with NaOH and process film. It makes perfect sense that anything that is strong enough to alter PET would hard-to-impossible to clear from the plastic. NaOH does indeed fog emulsion. (See post #90.) Traditionally, that implys its use in developers, but use is use.

Excellent work! I've got my fingers crossed tight for you. Although 3M assures me (and I believe them) there will always be PET film subbed for hydrophilic coatings, it's always cool to be able to go DIY all the way. Do you think you'll need to deal with any residual NaOH in the subbing? Perhaps a coating of plain gelatin (or maybe a bit of added acid?) between the subbed PET and the emulsion? Again, really cool stuff. Congrats! Also, I'm trying to pull together everything I can find on the ins and outs, ups and downs of gelatin with a new section on TLF: http://thelightfarm.com/Map/Gelatine/GelatinePart1.htm (It's a work in progress, but can't that be said for everything :) )

Thumbs up!

Photo Engineer
07-22-2012, 01:51 PM
Let me clarify that post.

Strong base can affect raw emulsion during coating and drying due to pH shifts and the low (relatively) water content of the emulsion during coating. Therefore, if the surface pH of the substrate is alkaline, the emulsion may be fogged.

But, if you have a strong base in a developer, the effect is much lower and it can be used there safely. Many developers contain very strong bases. However, the strong bases give high activity and if this is not controlled you can get fog there too.

So, as a summary, you should coat at pH 5.5 to 7 for best results. Above that and you can induce fog and this happens in the presence of strong base. Ammonium Hydroxide is even worse due to its solvent effects. Strong base can be used in developers with no serious problem except their high activity. This can lead to fog.


07-22-2012, 05:28 PM
PE, next time I coat I will check the pH of my emulsion. If it is too high, what is best to use to lower it?

Photo Engineer
07-22-2012, 06:17 PM
To make the pH more acidic, you should use either Citric Acid, Sulfuric Acid, or Acetic Acid. These should be very dilute. Do not use Nitric Acid or Hydrochloric Acid. If you wish to use Ascorbic Acid, that adds a twist to the situation as it is an antioxidant and a developing agent. It can be used, but has some side effects.


07-22-2012, 10:34 PM
Thanks, PE. I will check into that.

Last night I made a coating that has turned out to be very fogged. The PET was washed very well in fresh water, so I don't think that was the problem. It was a small coating, about 10 or 12 ml, as I wanted to try photo-flo (5 drops) again and glyoxal plus erythritol . Now I forgot to dilute the glyoxal and used 1 ml full strength. Anything to point to there as a foggant? I'm suspecting the stock strength glyoxal since I have used photo-flo and erythritol before, although not together, without problems.

The good news is that while this coating is unusable for photographs, its adhesion properties are very good.

Photo Engineer
07-23-2012, 09:20 AM
At that level, you should have very hard coatings. I have never tried glyoxal at that level.


10-08-2012, 11:43 PM
I really like longevity, and for film Polyester seems to be the best,
wikipedia mentions that some film has it as a backing,
but it seems like most use volatile acetate base,
are there any brands that still use polystyrene base for 135 or 120?
Or is the only option now to make my own polyester film with emulsions?

10-14-2012, 04:01 PM
The triacetate that's used for film is very stable in its own right, but my understanding is that yes, polyester is the best base for longevity and dimensional stability.

Not sure about polystyrene...

Kodak large format films are all on polyester, and I've seen some 135 film on polyester as well (Rollei I think...)

10-15-2012, 01:18 AM
Ya, triacetate is good for 50-100 years or so, but then it's prone to turning back into vinegar.
polyester however is rated for 1000+ years when it comes to archival purposes.
i believe in reincarnation, so would love to have previous photos available.
Though of course also good for grandchildren and the like.
polyester films can outlive fiberbased prints .

polystyrene was actually a typo, though apparently it's used as a base
for kodalith ortho films http://albumen.conservation-us.org/library/c20/calhoun1959.html
it is however mildly biodegradable, by certain bacteria.
btw, perhaps could melt clear plastic bags (polyethylene) and roll them into film.
I've melted plastic bags and made toy boats out of them.
though not sure the film would be hydrophilic.

Thanks for that info about the Rollei polyester base-films, i'll get some :-).

10-15-2012, 09:50 PM
Be careful with polyester though, it pipes light! I agree though, an amazing plastic really. UltraStable made a white polyester base for the transfer of their carbon prints; owing credence to the thought that it might outlive fiber based papers.

There are polyester films available, and some chemical etching techniques show promise for making it hydrophillic.

06-17-2013, 04:59 PM
Hi to you all, I've been trying to find a supplier for Grafix Dura Lar for wet media on Continental Europe.. I really have contacted quite a lot of firms, including Fotoimpex in Berlin. Most of the time a negative reaction and even worse no reaction at all. Does anyone out there in the US have better contacts with suppliers as to find out why this apparent backwardness in Europe exists. At the moment it seems there is no other option than to order in the US or in the UK. Thanks a lot for your answers. I still don't think I am the only one searching for it. I am happily brewing my Lightfarm Emulsions but I would like to "spoil" more than just glass plates and anyway I did read that a new the lightfarm Tutorial on Roll film is scheduled for mid July, I'd like to have my materials ready by then. I also asked in German and Dutch, to no avail. Thanks a lot for your help. Henk

06-19-2013, 11:43 PM

I don't know if you can order through Amazon, but they list Duralar Wet Media in sheets and rolls. It's not a photographic product, per se. Have you tried art stores? That is where I bought mine. If they don't recognize the Graphix brand, talk to them about wet media mylar films. It seems that critical thing you are looking for is 4 mil (.004 inch) thickness. (I don't know if or what the metric equivalent is.) If you can find a 4 mil wet media film I believe they are all really the same, or very similar, material.

-- jason

07-16-2013, 12:56 PM
Hi Jason, thank you. I can order Dura Lar in the UK but it seems a bit funny not to be able to order Dura Lar on Continental Europe.Could anybody who knows Mirko of Fotoimpex perhaps prod him a bit to start and stock Dura Lar for wet media. I contacted Fotoimpex but no reaction. I have a bit of emulsion in the fridge, I am going to use it on an old piece of 120 film I still have, but that will not last for ever. Thanks, Henk.

12-31-2013, 04:28 PM
Finally, I have obtained a (complete) copy of Glafkides "Photographic Chemistry." One of the things I was interested in was a subbing recipe for acetate. At this point most of us are using wet-media PET films for actual coatings but I have been interested in subbing acetate one, because I never got it to work and two, because I have a small pile of acetate. Note, this is cellulose diacetate, not triacetate, according to the manufacturer website.

I am aware that many here say that Glafkide's book has errors and omissions. OK, so knowing that, a subbing recipe given in Glafkides book for acetate is not terribly different from many I have read in patents. Here it is:

Gelatin 1g
Acetic Acid 2g
Water 4ml
Nitrocellulose 1g
Acetone 60ml
Methanol 32ml

According to the book, page 468, the gelatin, acetic acid and water are allowed to soak for a few hours and then melted in a water bath. The nitrocellulose is then added. So far, so good. Here is the problem: On adding the acetone, a white insoluble rubbery substance forms immediately. I assume the white substance has something to do with the gelatin. Any ideas what this white substance is and how to avoid having it form?

I've had this happen most of the time when making acetate subbing formulas, which is one of the reasons I gave up on it. The acetone used is sold as 100% Acetone fingernail polish remover and the ingredients are given as acetone and denatonium benzoate, which is a bitter substance used at very low concentration.

Thanks for any help,

Photo Engineer
12-31-2013, 06:21 PM

In the first place, that appears to be a formula for subbing cellulose nitrate base not cellulose acetate. Also, the concentration of the Acetic Acid is not specified. I assume it is glacial AA. Heating too long or too hot will denature the gelatin.

Acetone should be free of ALL contaminants. It should be chemically 100% Acetone and not have any denaturants.

If you can get a better formula and better acetone, you will be better off. That formula is close to the ones I have seen though. Gelatin, AA, some plastic and a solvent. I'll take a look at my formulas here, but no promises. Everything I have worked with was presubbed.


12-31-2013, 07:18 PM
Hi PE,

Sorry, yes it is glacial Acetic Acid. What does denaturing the gelatin mean?

Pre-subbed is definitely the way to go. The wet-media Grafix PET is great stuff, no frilling and no stripping but a bit on the pricey side.

Not too long ago I obtained a 400 foot roll of clear 35mm triacetate film leader. It was manufactured by Kodak and is also pre-subbed. I suppose it is really just uncoated film base. Maybe it didn't meet their quality specs for use in a coated product so they sold it as leader.

I will still probably get some pure Acetone. I do wonder about the denaturant in the acetone I have, though.

Glafkides gives a simpler formula on page 467 for nitrate subbing consisting of:

Gelatin 1.2g
Acetic Acid (glacial) 2g
Water 5ml
Methanol 92ml

Glafkides doesn't give a specific formula for subbing triacetate.

Anyway, thanks and Happy New Year!

-- Jason