Subbing siliconized (Bo)PET (mylar / Estar) film for gelatin adhesion

[koraks]

A long shot, but worth it, given the broad knowledge base of Photrio...

I've got this roll of BoPET film that I'd like to put to good use. AFAIK BoPET = mylar = Estar =Melinex etc., but the roll I've got is silicone coated on both sides. I understand it is intended for things like archival storage (separator sheets) and release film for adhesive tapes etc.

The one application that stands out to me would be as a temporary support for carbon tissue, which is basically gelatin with a little pigment and some sugar. Now, the problem is that the absolute beauty of this material is that basically nothing sticks to it. It's about as hydrophobic as our cat (which is *very* hydrophobic indeed), which of course doesn't help when trying to get gelatin to become intimate with it.

So my question is: is it feasible to sub this film at home so that a rather thick gelatin layer (1mm wet height) will stick to it?

I've tried the obvious experiments with a 1% solution of gum with a hardener, but it just beads on the surface. Essentially any kind of aqueous solution will do this, so that rules out quite a few options. Basically the things I've done (successfully) to make gelatin stick to glass won't work with this stuff. I can imagine somehow mechanically roughening the surface (a.k.a. grinding the beejesus out of it), but I discarded this avenue because it's going to be ridiculously time consuming / labor intensive.

I've very briefly gone through some patent information, which turns up all sorts of rather Byzantine procedures devised by Kodak, Fuji & Friends, which are undoubtedly very effective (after all, Estar!) but also prohibitively industrial in nature.

Throw some witchcraft at me if you've got any!

 

[CMB]

Try TSP (TriSodium Phosphate) to etch the coating/PET

 

[DREW WILEY]

I obviously responded already on a different forum. But you don't want a cure worse than the disease. I don't know about EU rules, but TSP has been banned in most of the US for more than two decades due to its severe tendency to produce algal blooms in wastewater. Often EU enviro rules are even more stringent. What is sold being here as "T.S.P" is not in fact trisodium phosphate, but a common metasilicate substitute, basically a liquid abrasive which tends to leave its own residue. If your try that, it's going to involve an awful lot of effort and rinse water, and probably prove useless anyway. Silicone treatments are engineered to be especially tenacious. Any little bit of it left behind (and most of it will be) is going to break a bond. Silicones are inherently classified as "bond-breakers".

 

[CMB]

I have been using this stuff to prepare (etch) PET to use as a temporary support in place of albumen coating and it seems to work well: https://savogran.com/pdfs/TSP_PD.pdf

 

[DREW WILEY]

Where do you legally get that in California? - especially in the vicinity of a Marine Sanctuary? Check the fine print to see if it contains phosphate or not. In any event, it's unlikely its going to successfully remove a silicone over-layer.

I realize that you have a great deal of experience in true pigment printing; but have you ever messed with this specific material?

 

[CMB]

Well yes, I now use it (as I said) to prepare PET for use as a temporary support for a carbon transfer print. I believe I get it at Home Depot.

But I have no idea how it will act/react to a silicon coating.

 

[DREW WILEY]

OK. You did in effect answer, No, you've apparently never used this product in relation to attempting to remove a silicone coating; and, yes, it is predictably Home Depot which sells this phosphate product in complete disregard for either the law or local codes; but that kind of cavalier attitude is characteristic of them.

Otherwise, Glad to see you're still active and contributing to the learning curve of yet another generation.

 

[AgX]

-) PET to be coated at the industry is neither subbed nor etched, but corana-activated (radicals-forming)

-) this can be done by the amateur

-) preparing a siliconized surface seems impractical to me, in any case uneconomic

 

[nmp]

TSP can be bought at the hardware store - it is used to clean decks or something. Even Walmart has it.

Robot or human?

Secondly, koraks is not dealing with PET. Silicone coating on both sides supersedes it so what works for PET does not / will not work here.

:Niranjan.

 

[DREW WILEY]

I don't know a single legit company that sells real trisodium phosphate in a bottled deck cleaner anymore - it's all metasilicate "TSP substitute" - and I've distributed more national brands of deck cleaners and coatings the sum of all of you could even mention the names of, perhaps the biggest selection in the country during certain decades overall; even been involved in the development of some of them. If seeing alleged TSP in a hardware store, look at the fine print or MSDS sheet to see what the actual ingredient is. Can't imagine it would be legal in Maryland either, since that State also has a significant coastal footprint, but don't really know the specifics in that case. WalMart? Just like Cheapo Depot - complete disregard for all kinds of laws.

 

[nmp]

I don't know a single legit company that sells real trisodium phosphate in a bottled deck cleaner anymore - it's all metasilicate "TSP substitute" - and I've distributed more national brands of deck cleaners and coatings the sum of all of you could even mention the names of, perhaps the biggest selection in the country during certain decades overall; even been involved in the development of some of them. If seeing alleged TSP in a hardware store, look at the fine print or MSDS sheet to see what the actual ingredient is. Can't imagine it would be legal in Maryland either, since that State also has a significant coastal footprint, but don't really know the specifics in that case. WalMart? Just like Cheapo Depot - complete disregard for all kinds of laws.

Never knew this. Looks like some are so-called TSP-substitutes and some just have some washing soda additive to bring down the phosphorus to the level allowed. There ssems to be 18 states that have banned and MD is one of them. I am guessing they are selling the alternatives here, not the real thing - as you first suggested. I bought some time ago to use as a bleach for cyanotypes. Now I don't know, may be I was just using sodium carbonate and some TSP - not 100% TSP.

:Niranjan.

 

[koraks]

Guys, thanks for the thoughts, suggestions and discussions; I truly appreciate all of them. I might try TSP, but given Drew's arguments it will at most be to see if/how it works but not to process any significant amounts of the material.

There's a good chance that this roll of material will see use in another function, but given the fact that it's taking up space, I thought I'd try and put it to use before I get sick of moving it around because it's in the way. If it has a function, it's easier for me to tolerate its presence.

Of course, what doesn't help is the fact that the documentation of this material is not specific to the exact nature of the coating; it just says "siliconized on both sides" (literal translation). I'll see if I can locate a proper datasheet, who knows this would help some.