Film making, sort of

[Brazile]

Not a perfect match in the subforums for this topic, but it's been so long since I bestirred myself to make a new post, I probably missed an obvious choice. I've been meaning to get to this for a while, not sure what keeps me from taking the time. Anyway...

As some of you will remember, a while back (geez, 11 years ago, yikes) I took a workshop in making gelatin emulsions. It was the second workshop I took in the historic process workshops then taught at Eastman House (now George Eastman Museum) in Rochester, and the one that really grabbed me. I've been making, coating and shooting them ever since. While I won't say that I've mastered the process, I think it's fair to say that I've reached journeyman status, as last year I got the opportunity to help teach a workshop on the subject and it went very well. But that's another post (that I should have made but didn't. May well do a separate one on that, as it was an interesting experience. And maybe one on all the other processes I ended up learning in about a dozen years of different workshops.)

Anyhow, fast forward to the present. I just got home from a week of serving as a lab assistant while Mark Osterman (retired from Eastman) worked on making some batches of emulsion and working to coat them on film (rather than the glass plates I normally work with). He'd managed to collect an old Polaroid Research DIY film coating machine via RIT and an ex-Kodak perforator, and rigged a setup for slitting the master roll that came off the machine. In it's current configuration, it can only coat 6-7 ft (a couple meters) of film, but that's enough for a 36-exposure roll of 35mm or a standard roll of 120. He was getting ready for a visit from the conservation lab at SUNY Buffalo to do some demonstrations, and it was an opportunity to for me to mess around with the cool toys and help him out as an extra pair of hands and eyes as we went through the process.

For the project, we made two emulsions, the first being "MO-1880", which is a blue/UV-sensitive emulsion that corresponds to what people were making about 1880. It's slow but very clean and fine-grained. As to speed, ISO doesn't really make sense with blue-sensitive, as it's so dependent on the spectrum of light used, but it's probably reasonably close to ISO 2 or 3. Can be a bit faster in good (blue or UV heavy) light, and a lot slower otherwise. Then we take some of that base emulsion and sensitize it further to make it a bit faster. There are different techniques for this available to the DIY maker (that's yet another post) but this time we're going for a fairly simple one of adding a minute amount of sulfur, in the form of a dilute solution of sodium thiosulfate (yes, fixer) that gives it a boost in speed. If you're lucky, you can get to ISO 12 or so in good light, and more is possible with other techniques, at the risk of a bit more fog, and possibly larger grain. The grain is generally a non-issue with plates, being large format, but can be more of a problem for smaller formats. For other projects that I can't talk about yet, Mark is wanting something corresponding to common 35mm film from about 1925, so we're aiming for that, calling the result "RM-1925" (RM for Ron Mowrey, who worked with Mark and Nick Brandreth to formulate some faster emulsions before Ron sadly passed a few years ago).

Once we made the emulsion we wanted to use, we loaded up a film coating machine he'd acquired that is an amazing Rube Goldberg (or Heath Robinson if you're from the UK) kind of thing: made from an old Sears abrasive belt grinder and some custom machined parts at Polaroid Research back in the day, it was donated to Rochester Institute of Technology (RIT), and then to Mark when they stopped using it. It has a coating head made of two pieces of machined stainless steel separated by a plastic shim that sets the gap that the heated emulsion flows through. Then a length of film base is attached to the platen of the old grinder and around the rollers, then clamped down and sliced to make a continuous loop. The emulsion is loaded into a separate machine that consists of a stainless steel syringe driven by an electric motor through some gearing (to allow for multiple speeds) that drives a lead screw attached to the plunger of the syringe. The syringe is connected to the feed head via a flexible tube. Coating requires mounting the film base, splicing it cleanly, getting it centered and running true, positioning the splice just past the coating head, loading the syringe with emulsion heated to the right temperature, then installing it in the pump, connecting the hose, running the pump to start the emulsion flowing (you can see it travel through the tube), then, when it just reaches the coating head, turning on the belt drive on the coating machine and hurriedly adjusting the positioning of the coating head so the flow spans the film base correctly. Then you let it run until the whole loop is coated and stop the pump and pull back the head before it tries to lay more emulsion down on what's already been coated. Whew!

Long story short, we were able to do this, and hung the film to dry. It's usually dry in a couple hours and can be slitted and perforated. Oh, did I mention that Mark managed to cadge a small research-level perforator that was being disposed of? Well, yeah, not something that just anyone can get their hands on. We didn't get to that part while I was there, but next time I'm over I'll ask for a demonstration of that.

Anyhow, thought you guys might find it interesting. Below I've included a few snapshots from the week:

Precipitation of the silver into the salted gelatin:



The acetate film base, obtained from Ilford, for testing:



Mounting the film base on the coating machine and splicing it:



Mark, with the coated film base after the fun:

[Julio1fer]

Ultra cool!

[scott]

The acetate base off the roll looks about right for slitting to ~4x5. When y'all get the RM-1925 working, I'd be interested in testing it on 4x5 for ya...

Seriously, very cool project. Legit engineering (chemical and mechanical). Appreciate the sharing. Good job.,

[Brazile]

Hmm, yes, now that you mention it, that film base is just about right for that. What do you know about that?

The acetate base I think is a little flimsy for sheet film, though, and might be a bit annoying in a film holder. That said, he has a roll of polyester base, too...

If I ever happen to be hanging around Rochester when we have the time and he can be talked into coating a strip of polyester, it might just happen. But he has a lot going on, and I'd have to do some serious tap dancing to distract him from whatever current project he's working on, I expect. But you never know! In the meanwhile, making plates is a lot easier. You just need a plate holder or two. That, I can supply, RM-1925 and all. In fact, my next batch of emulsion is likely to be something like that, or possibly even faster. Fingers crossed!

As for the engineering: yes, it was both ingenious, and interesting in that there's very little that a determined DIY-er couldn't make. The trickiest bits: the coating head and the pump. Everything else is pretty simple erector set stuff, and a lot of the necessary parts are available for the DIY CNC crowd: rollers, step motors, lead screws, etc. The platen could be taken from something like the belt grinder body or a little bench-top jointer.

The coating head could be reproduced by a machinist who's OK with working stainless steel; it's just two slabs ground with a bevel along one edge that mate with a (plastic) shim between them to form the coating aperture, a couple of locating pins, some threaded holes to lock everything together with screws, and a through hole with a threaded mount for the hose connection.

The pump is really just a stainless steel syringe connected to a motor that pushes in the plunger. There are other ways of doing this. The gearing would be a bit fussy to reproduce, but there are other ways of metering the pumping rate, I expect, so I wouldn't bother with gearing. Just controlling the motor with a variac or similar could work fine. If you are or know an analog EE, I'm sure it could be cobbled together easily.

All that said, it's too much work for my purposes; I'm pretty happy with glass. But it's sure fun to play with. The main difficulty for the DIYer is the perforator; it would be difficult to homebrew, and unless you have connections at a film manufacturer shutting down facilities, hard to come by otherwise.

[scott]

I'm pretty sure the old Maco IR stuff was on acetate. That stuff was (and is - I still have some) a HUGE PITA. But never say never. I'll keep my fingers crossed. The MacGuyver aspect of your project is fantastic, though. My daughter has an ME degree from Lafayette, but (indictment of higher education) has no idea what engineering IRL actually is. My wife (ChE) and I keep trying to explain to her it's this kind of problem solving, but you know kids, won't learn from parents at this point.

Regarding plates, I've been watching 10x12 cams (Vageeswari, Asanuma, etc.) on eBay. Prices have DROPPED - unfortunately, though, they're all in Japan, and the sellers have watched their sales dry up with the tariffs. So, while I can get a 10x12 camera, with three bookform holders, for under three bills, shipping is over $300. That said, I kind of want to do that specifically to dive into this. Thanks a lot, pal-o-mine. I may still try to finagle that somehow, especially after seeing the Letchworth results.

[Brazile]

I will put the possibility on the list of things to try to make happen if I get the right opportunity. Like I said, you never know!

I do hear you on modern life and its lack of opportunities for kids to really solve practical engineering problems. It's just too easy to grow up without making even simple things work. I nearly did, and it's only more so now. That said, my son, after I'd basically given up on his being interested in such, suddenly got focused on building out a woodworking shop and making things. Something happens when guys get settled in their careers and the kid gets a bit more self-sufficient that makes them finally start thinking about things like this I guess. Helped him build a bench and a toolkit, and (the crucial bit) he's started working on it even when I'm not around. Maybe there will be someone to take on all these tools when I'm gone after all...

As for the 10x12...woo, I hope you can make it work! I *think* I have a box of expired 10x12 film around here somewhere I picked up for a song. If so, it's yours for the taking if you manage to land one of those bad boys; I have enough ULF projects around here to last a lifetime without yet another format. Happy to pour you some plates to play with as well, that's easy.