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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.

PE

kb3lms
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.

PE

streondj
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?

holmburgers
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...)

streondj
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.
http://comminfo.rutgers.edu/~lesk/spring06/lis556/life-expect.pdf
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 :-).

holmburgers
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.

Polder
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

kb3lms
06-19-2013, 11:43 PM
Henk,

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

Polder
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.

kb3lms
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,
Jason

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

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.

PE

kb3lms
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

Photo Engineer
12-31-2013, 07:28 PM
Jason, that latter formula should work.

Denaturing gelatin is the process by which the tangled strands of gelatin change shape and can no longer dissolve in any liquid. It is too ionic for organic solvents and too non-polar for water. It forms a gooey whitish mass. I've done it many times by accident.

Sometimes, all you have to do is reheat the mess and when it gets hot enough (30C - 40C) it will redissolve.

You might try that. And watch out for the nitrocellulose. That is nasty stuff.

PE

DannL.
12-31-2013, 09:53 PM
Interesting conversation, indeed, and probably way out of my league. But . . . I've coated a number of 2mm glass plates now, 4x5 through 8x10 and subbed with a thin layer of Minwax Polyurethane (spayed on). I've tray processed these plates and have had no lifting whatsoever. If that is of any value.

Prior to learning about the Minwax, I couldn't keep the emulsion on the plates beyond the developer tray.

Photo Engineer
12-31-2013, 10:19 PM
In the GEH workshop, the students coat directly on glass and have no adhesion problems. They don't even need hardener.

However, coating on film is different. Film repels water much more vigorously than glass does.

PE

Andrew O'Neill
01-01-2014, 12:20 AM
I wonder if Pictorico would work. It would probably coat well, but major issue would probably be curling since it's quite thin.

Photo Engineer
01-01-2014, 01:13 PM
Pictorico is intended for digital printing. As such, it has a mordant on the surface which can react with many chemicals. My tests so far have given me heavy brown stains in the Dmin region of all coatings made on any form of digital print material (paper or film).

PE

Andrew O'Neill
01-01-2014, 03:02 PM
Thank you, PE.

DannL.
01-01-2014, 11:27 PM
So, I took a sheet of 124CSS-VC Copier Transparency Sheet to see if it would accept a thin layer of Minwax Polyurathane. And it did. With that I expect it would accept the emulsion that I've been using. The sheets "may" accept an emulsion without subbing. Not something I plan on testing. One problem I noticed though . . . these sheets are magnets for dust. Handling them created a potential within the sheet.