US 4076772 describes a method of coating gelatin on PMMA (= "plexi"): "A poly(methyl methacrylate) sheet is coated with nitrocellulose, the nitrocellulose is denitrated, and a gelatin solution is applied (...)."
Originally Posted by daveandiputra
Ammonium sulfide is used for denitration.
That's a very interesting.
Originally Posted by dwross
As an aside, photopolymers (hydrophilic or hydrophobic) based on free radical polymerization, may actually provide improved adherence to a great many kinds of substrates. Free radical formation seems to be the principal reason why corona treatment "works".
For the moment I've only been playing around with setting and hardening gelatin, played with the idea of gelatin on it's own, but it tears way too easily.
Making crude cellulose acetate, and dissolving and setting and evaporating it is fairly simple process, you can make whatever thickness you want, but you can't exactly make a roll that way, but you could build a very large trough, or long trough with a sheet of window glass. You can make even better acetates with the addition of acetic anhydride.
Eventually I would like to try my hand at coat with an array of fine spray nozzles over a moving transport through a simple machine, but I don't know yet.
That's interesting, the idea of using gelatin or some other colloid as the base (I think collodion's been used in the past too).
The idea of casting one's own base is zany but wonderful. I'm glad someone's thinking about it.
I wonder if there's some modern polymer that you could "cast" in a similar way to cellulose acetate, with better properties.
Mark Osterman teaches and demonstrates the making of film support in one of his workshops. It is not all that hard.
IIRC, that demo was with nitrocelluose film support.
I have a demo of TAC (CTA) being made and hand coated.
I didn't know Mark did that, is it indeed nitrocellulose? It makes sense he'd prefer something flammable... :laugh:
Ron, do you recall if Jim had investigated this 3M support for his non-staining base?
Would love to know how to make cellulose triacetate!
IDK which type of support Mark made. You might ask him. Same for Jim Browning. He tried a number of supports before he settled on the one he did.
I just wanted to ask you a bit more about the 3M films. This is really a great epiphany; and I think that although you mentioned them on the Light Farm that this is the first place where they're mentioend by specific product name(?).
How would you compare the subbing to DuPont 583 (PF melinex)? Both will be destroyed with pre-wetting of any kind but DuPonts is very resistant to abrasion and even oily fingers (trust me, I tested it... after eating fried chicken... ;)). How about the 3M stuff?
Also, what size did you get it in if you don't mind me asking? Is it in a roll, or sheets, how long and how wide? Did that company offer any kind of custom slitting or size options? I'm just rather curious about all these bits of minutiae.
Thanks again for bringing this to everyon'e attention; I'm quite excited by it.
edit: Here is a list of potential suppliers.
Actually, I think that poor scratch resistance of subbed films (both 3M and Dupont) are the material's Achilles heel. The Dupont film that The Formulary sells has minute scratches. They're almost impossible to avoid. I'm getting much better at handling film, but (so far) it's a guarantee I'll end up with a scratch somewhere in any given batch of finished film -- usually from the final cutting-to-format stage. I'm pretty religious about wearing cotton gloves, so I can't speak to grease resistance. I can tell you that you don't want to sneeze on the stuff :whistling:.
The good news is that the scratches are essentially microscopic. (More info: http://www.thelightfarm.com/cgi-bin/...tent=28Nov2011 )
One issue that I'm still working out is that the 3M film doesn't seem to hold dry emulsion as well as the Dupont if the coating temperature is too high. I've got the right temp for my emulsion figured out, but I'm not motivated to test, test, test all parameters, just to obsessively blog, so I'm hoping others will join the Light Farm 'research team' and share their findings. (A girl can always hope.)
The 3M vendors I talked with all would do custom cuts for a price. I never asked about sheets. I think the film is only available in rolls. I was able -- and quite happy-- to take remnant end pieces in various widths -- for both the thin and thick films. I got a great deal that way. My only requirement was that no one roll weighed more than 50 pounds or was wider than 36 inches.
You're right about hydrophilic subbed PET being a game-changer. Seriously, there is now absolutely nothing standing in the way of really, really good diy film, plates, and paper (except of course, the exact same things 'standing in the way' of all non-instant, non-digital photography -- enough time and space to create.)