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gmikol
05-29-2012, 08:23 PM
Just want to add a quick note to this thread regarding Dura-Lar Wet Media film. I was at the art supply store the other day, and they had a pack with a dinged-up corner that was significantly discounted. I have no use for it, really, but I grabbed it thinking of this thread. If anybody wants to try it (US only, probably, otherwise postage gets too high), I'd be glad to send out a few 11x14 sheets rolled in a tube, or cut down to 7x11 for mailing flat. I'd ask that you reimburse me for postage and shipping materials. If anybody's interested, let me know via PM.

I took a little corner of it and ran it under water. There is definitely a clear coating that got a bit slippery for a second before it rinsed off. Have no idea what it was. The highlighter markers that I had laying around (which I thought were water-based) didn't behave any differently between the wet media film and regular dura-lar, so maybe they weren't water based, or...

Anyway, just wanted to mention this. If it works, it might be a good option for those who wish to avoid the larger purchases required for the 3M film if you're making sheets.

--Greg

holmburgers
05-29-2012, 08:56 PM
Greg, funny you mention this. I emailed Grafix a week or two ago asking about the wet media film with gelatin and they were intrigued, so they sent me a couple sheets to test. Just arrived today!

I only say something to account for why I won't be raising my hand, but dang what a coincidence. :laugh:

newcan1
05-30-2012, 10:45 AM
I was wondering -- I use imagesetter imaging film in a small offset printing business that I have. Often the film gets messed up (someone forgot to proof the page, etc). If I bleach the emulsion off of the films that cannot be used to make printing plates, will the substrate that remains be suitable for coating with emulsion without further preparation?

This would mean that instead of the used film being hazardous waste, the bleached off emulsion would be, and I would have to figure how to dispose of it, but the clean substrate could be used for coating if I ever get around to making my own emulsions. And I have quite a lot of the stuff.

holmburgers
05-30-2012, 12:41 PM
Well, if you literally bleach off the emulsion, probably not. But, if you bleach out the silver, then the remaining clear gelatin will make an excellent substrate. So yes.

But most subbing layers on film are one-and-done. For instance, if you wet the Photo Formulary melinex before coating, it becomes useless. That's why I say that if you literally mean removing the emulsion from the film, then the remaining raw PET/TCA will probably not accept a coating.

newcan1
05-30-2012, 01:40 PM
OH - OK - thanks for the explanation. I had read some of the threads here but only quickly, and I had thought that the subbing process modified the surface of the plastic to accept an emulsion, in a way that would permanently affect the plastic. I did not realize it only worked once! I was talking about removing the emulsion - I thought that bleaching and fixing the existing emulsion could be a bit costly, but it is worth considering. Ferri bleach and fixer do last rather a long time.

But wouldn't adding a new emulsion make the resulting total gelatin layer(s) rather thick?

holmburgers
05-30-2012, 02:16 PM
I suppose adding a new layer would make it somewhat thick, but not necessarily too thick. Any machine coated film is going to have a rather thin coating to begin with, so it shouldn't add much more than several microns.

As for their subbing treatment, having to guess here, I would bet that they coat with an inline corona discharge unit. The pre-subbed substrates on the other hand probably receive a corona treatment, and are then treated with an ultra-thin subbing layer for coating later.

Photo Engineer
05-30-2012, 03:50 PM
Some subbing layers can work more than once. I would not vouch for quality though due to induced imperfections.

PE

newcan1
05-31-2012, 06:39 AM
If I did remove the existing emulsion with chlorine bleach, could the remaining substrate be re-subbed?

Photo Engineer
05-31-2012, 09:04 AM
Probably not at this point. It would have to be re-bombarded with a static charge. That is, if the subbing is gone.

PE

holmburgers
06-05-2012, 10:43 AM
I'm posting this just for reference; a technique for treating raw PET with potassium hydroxide to roughen its surface texture and thus create a hydrophillic subbing. Umut came across it.

Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 12, No. 2, pp. 118–120, March–April, 1976. By I. Astrina, S. V. Vlasov, R. D. Gorak, Yu. V. Moiseev and Ya. A. Serednitskii

http://www.springerlink.com/content/kgwn7n442v57u30q/

Mustafa Umut Sarac
06-05-2012, 10:55 AM
Thank you Chris to heads up.

kb3lms
06-05-2012, 01:08 PM
Thanks Chris and Umut. Looks interesting. Does anyone have access to the full article? There are also some patents that refer to the same sort of idea. Would it be likely to work with sodium hydroxide as well? The first page mentions polycarbonate as well as PET. I've got a whole roll of polycarbonate film to experiment with. I'd figured out a way to sub it but it didn't come out looking very nice and wasn't as flexible as when I started.

Then again, I haven't made much of a dent in the support Denise sent me. :-(

Photo Engineer
06-05-2012, 02:00 PM
Sodium Hydroxide would be as good as Potassium Hydroxide but you may need a bit more of the Na salt to adjust for molecular weight and for the very tiny decrease in alkalinity of the Na.

PE

holmburgers
06-05-2012, 02:18 PM
Ron, do you recall if you or Jim B. ever came upon methods for subbing PET? I remember that you mentioned researching this a bit in the past and I believe the answer was no. So, is this an epiphany, or something that perhaps you've deemed impractical?

Just curious; I'm gonna shoot Jim an email too.

Photo Engineer
06-05-2012, 02:35 PM
I really don't know what Jim tried. I don't think that he did any subbing experiments. I feel that if this were commercially feasible, then someone would have reduced it to practice, but I have never heard of it being used. Technically, it should work, but it may be impractical from some POV.

PE

holmburgers
06-05-2012, 02:39 PM
Thanks Ron; I'll report what Jim responds with.

I'm also interested in "flaming" methods of hydrophillisizing (is that a word?) PET. An inline blow-torch perhaps? Could be fun!

hrst
06-05-2012, 09:07 PM
AFAIK, flaming is quite difficult to control and is prone to deforming the material. It has been almost completely abandoned decades or half a century ago for corona treatment. I would use that effort to try your luck with corona which is very simple in theory. Still, the only real problem is sourcing the suitable transformers for low price.

Photo Engineer
06-05-2012, 10:05 PM
Have you ever thought of just running a blank sheet of Estar through a Xerographic machine? That may give it enough of a charge.

PE

hrst
06-06-2012, 09:55 AM
Haven't tried but it probably won't work, because what I found out is that it's not the charge but the quickly toggling charge that causes the surface treatment. Therefore, DC did nothing but just gave the static charge. It needs to be high-frequency AC.

kb3lms
06-08-2012, 10:19 PM
The idea of etching PET with an alkali metal hydroxide seems common enough in the patent literature and there is also mention of resin coating and, of course, corona discharge. The corona discharge method appears to be considered the state of the art for maybe the past 20 or so years, likely because it may be more controllable and easily able to be done as an in-line process step without chemicals.

Tonight, I did try a quick experiment with a 10% solution of sodium hydroxide in water, which brings the first problem: PET is hydrophobic so the solution runs right off. (duh!) What's an appropriate solvent for the NaOH? Perhaps ethanol or methanol? Would a wetting agent like photo-flo help? There were some references to ethylene glycol as a solvent as well.

-- Jason