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kb3lms
07-05-2012, 11:01 AM
Chris,

No, but I had often thought about it. I think Denise said it didn't work. If you want something that peels when dry, just use regular Dura-lar or the Clear-Lay PVC film.

Update on my Dura-Lar, I got it to work yesterday. The answer to the frilling at this point is erythritol, a sugar alcohol similar to sorbitol. It is available in any grocery store - brand name is Truvia, I think. I used the Walmart house brand. I will put the details of my current solution in the other thread, here: http://www.apug.org/forums/forum205/107336-help-hardener-films-frilling.html

Compared to all the films I have tried, this NaOH treated Dura-Lar coats like a dream. I think it will be my "go to" film base. I'd say put the Dura-Lar at the top of the list.

Umut, the credit goes to you for originally pulling this information out of the historical noise. Great find!

-- Jason

holmburgers
07-09-2012, 12:21 PM
That makes sense that a humectant/plasticizer such as erythritol would help out. I've used sorbitol for my dye-imbibition coatings and it's worked very well, though frilling was never a problem.

So a (somewhat) interesting development with Dura-Lar Wet Media. I coated 2 more sheets; 1 that was washed in hot water and 1 fresh sheet. Both coatings are sticking nicely to the surface, which is somewhat perplexing. My thinking was that the wash would destroy the subbing layer and I was hoping to find that it would peel off when dry. I'll cut both sheets and see if frilling is a problem at cut edges.

But as far as my limited testing can determine, Dura-Lar Wet Media is a reasonable option for a film base. Unfortunately it's a little thin, and isn't as ideal as a 7-mil substrate, but hey, it could be useful for a lot of things nonetheless. I too recall that Denise said this base doesn't work, and so that's why I'm somewhat confused. Denise, if you're reading, I'd love to hear more about your experience with it.

If indeed my tests are telling, it begs the question what do they use for their subbing layer? Subbed melinex is definitely destroyed by washing, so I had assumed that this would be true for most other subbings. Interesting...

Mustafa Umut Sarac
07-09-2012, 02:37 PM
what do they use for their subbing layer

They use that , read that book:http://www.scribd.com/doc/16314506/Vaccum-Deposition-Charles

VACUUM DEPOSITION ONTO WEBS,FILMS,AND FOILS

Mustafa Umut Sarac
07-09-2012, 02:52 PM
Photographic polyester supports with copolymer subbing layer
Toshiaki Yamazaki et al
Patent number: 4571379
Filing date: Feb 13, 1985
Issue date: Feb 18, 1986

Mustafa Umut Sarac
07-09-2012, 02:54 PM
subbing layer is LATEX

Photo Engineer
07-09-2012, 03:48 PM
We suspect that the subbing layer on the version of Melinex that we have via Jim Browning is a latex. Teijin and ICI both hold patents for subbing layers. IIRC, they both use latex.

PE

Mustafa Umut Sarac
07-09-2012, 03:56 PM
Thank you PE,

Above patent describes to manufacture Latex in 5 hours at 85 celcius degrees.

Umut

Mustafa Umut Sarac
07-09-2012, 04:34 PM
http://www.tappi.org/content/events/07place/papers/paisley.pdf

Who wants to make his her subbing layer needs PVDC Latex. Above paper gives hints about this material.

Umut

kb3lms
07-18-2012, 07:50 PM
Everyone,

Here's a scan of a 35mm frame of the PET based film. Other than the dust, I think this turned out really well. This was exposed and processed about a week and a half ago as a single frame cut from a coated sheet. The rest of the sheet was used for 6x9 negatives. Straight out of VueScan.

54102

One thing that I will note is that the left side of the frame has begun to detach from the base. The right half has not. But, the left side is where the film was cut, the right side was not cut. I didn't see any detaching in my three 120 6x9 negatives, though.

So, I guess there are still some things to work out. :)

-- Jason

holmburgers
07-19-2012, 10:07 AM
Looks good Jason, though a bit troubling about the delamination. Then again, it can't be too easy, right? :joyful:

kb3lms
07-19-2012, 01:12 PM
No, that would never be any fun! I have glyoxal now as well as sorbitol, so some different things to try. Also picked up some Everclear, which is available in Maryland. Now all I need is some time.

Chris, is your coating on wet-media Dura-lar still holding?

holmburgers
07-19-2012, 03:21 PM
Amazingly, yes!

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!

I'd encourage you to experiment with this wet-media stuff though, so we can say with confidence that it works.

In the meantime, I'm trying to think of some ways that I can stress the coatings to really see how good they're holding. Any ideas?

kb3lms
07-19-2012, 08:48 PM
Chris,

I will get a pad of 5ml wet media dura-lar. Got in this far, might as well try one more! The NaOH treatment definitely works but if we can get rid of it, so much the better. Another thing I think that might have something to do with stripping and frilling is pH of the NaOH solution. The last sheets I prepped I tried using a 1.0M NaOH solution rather than 2.5M. After processing a few sheets, I didn't think it was doing a great job and on a hunch I checked the pH which IIRC was around 11.7. NaOH should be higher than that, I think. Possibly the terepthalic acid and ethylene glycol are lowering the pH. After the NaOH sat in its jug over the 1 1/2 weeks since going on vacation, I now note a layer of grey powder or crystals on the bottom of the jug. I'm guessing this is terepthalic acid.

WRT stressing the coatings, yes.

1) Soak in an alkaline solution such as your favorite developer and see how long it lasts. At cut edges the water seems to work in an under the gelatin is adhesion is not good. This test is mine.

2) The scotch tape test: Take an x-acto knife (or similar, but razor sharp) and a ruler and cut across the gelatin. Cut through the gelatin but not the base. Attach a piece of tape, say 2 inches long, across the cut. Carefully pull up the tape to the cut, then rip up the rest of the tape as fast as possible. The amount of emulsion that peels off tells you how well it sticks. No peeling is obviously best. This came from a Kodak patent.

3) Wet stripping test: See US Patent 2014547, Babcock ass. Kodak, 9/17/35 Page 3. There is also a dry stripping test given but PET will not tear in the same way.

If you search some of the patent literature on subbing from the mid-1930s through the mid-1950s you can find a number of different tests. Kodak patents seem to have given the best information.

-- Jason

holmburgers
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 70F 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.

kb3lms
07-20-2012, 10:46 PM
Chris,

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

kb3lms
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
Jason;

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.

PE

dwross
07-22-2012, 12:55 PM
Jason,

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!
d

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.

PE

kb3lms
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?