Kodak Vision3 film is not really intended for still photography, but that doesn’t stop many photographers from using it. Companies like CineStill offer this film without the remjet layer, but I personally prefer the remjet-backed original. That of course does leave the challenge of dealing with the remjet when processing this film. Fortunately, this is pretty easy and it does not require any specialized chemistry or equipment.
So what’s this remjet stuff , and why is it on cinefilm to begin with? After all, it’s not on regular still camera film (C41, E6 or B&W) – what’s up with that? Well, cinefilm is used in a more demanding environment, especially mechanically, than still film.
Cinefilm generally runs through the camera at 24 frames per second. Depending on the taking format, this works out as something close to 0.4 m/s. This is a decent speed and it creates the risk of scratches and static buildup and discharge as the film runs along components inside the camera. This means that some form of mechanical protection of the backside of the film is desirable, and remjet offers this. Coincidentally, it’s also quite slippery, so it reduces friction between the camera’s pressure plate and the film as it travels through te camera.
Moreover, since remjet is electrically conductive, it also prevents electric discharge, which could show up as intricate lightning patterns on film. ‘Fun’ fact: this actually plagues 35mm film confectioning from time to time; notably, some recent batches of Fomapan 35mm film come pre-exposed with such patterns from the factory!
Another important function of the remjet layer is to prevent halation. This is what happens when strong light hits the film and bounces around against e.g. the film and the pressure plate of the camera. It tends to show up as red-colored auras around strong lights – if you’ve ever shot CineStill film, you’re probably familiar with it.
So, what actually is this stuff? Apparently, film manufacturers took inspiration from the pharmaceutical industry and decided to use cellulose acetate phtalate (CAP), a polymer that happens to be quite resistant to acidic environments. It’s therefore used for drugs that are designed to survive the acidity of the stomach. For remjet, a large amount of carbon black (soot, basically) is mixed in with the CAP, and this is together deposited as a layer on the back of the motion picture film.
Remjet-backed film is easily recognizable because of the jet black backside that’s somewhat oily/greasy in appearance. The remjet layer also appears a little more matte than the bare film base.
Superia 200 C41 film without remjet to the left, remjet-backed Vision3 250D to the right.
Removal of the remjet layer in labs that process motion picture film is done through a combination of chemical softening of the CAP, powerful water jets spraying off as much of the stuff as possible and finally mechanical removal with a sponge roller. All this happens prior to development, so when the film is still light sensitive.
In a home lab setting, it is of course not very practical to set up something like this. Fortunately, if we just process the odd roll once in a while, we don’t have the kind of productivity and speed requirements a proper lab has, so we can cut quite a few corners. So let’s break it down to the essentials.
The removal of remjet essentially consists of two steps: (1) softening the CAP polymer, and (2) removing the softened remjet material from the film.
For the softening (1), the official Kodak approach is a ‘pre-bath’ based on borax, sodium sulfate and sodium hydroxide which is designed to hit pH9.25. At this pH level, the CAP material softens, but it doesn’t actually drift away from the film. This is apparently done to prevent remjet floating around and settling on the emulsion side of the layer, where it’s far more difficult to remove.
The following step, removal (2), is essential. It’s important to note that remjet is not designed to be removed by only chemical means: physical removal is really necessary. The Kodak way is a combination of water jets and a sponge or ‘rotary buffer’: basically soft roll-mounted brushes rotating at high speed along the film, whipping the remjet material away from the film surface.
What can we do in our home lab to mimic these steps? Turns out that the ECN2 (or C41, if you want to cross-process) developer itself actually works very well as a softening bath. Yes, it works at a higher pH and as a result, some of the remjet actually washes off during developer. I personally use my developer one shot, so I don’t worry about it, and there doesn’t seem to be any noticeable deposition of the remjet material onto the emulsion surface. So in my own workflow, I simply skip the pre-bath remjet softening step and just have the developer fulfill this function.
It also turns out that a subsequent acidic stop bath doesn’t harden the remjet; while it stabilizes it so that no further remjet is dissolving or dislodging into the processing chemistry, the remjet stuff itself remains very soft and easy to remove. The upshot of this is also that the bleach and fixer do not get contaminated with remjet, unless you very vigorously shake the processing tank (for which there is no need).
So I leave on most of the remjet until processing is done, and I even wash out most of the magenta sensitizing dyes with warm water before proceeding to the actual remjet removal step. And this step is really very simple.
I fill a decently sized tub with water with a little handsoap added to it. I then take the reel with the processed film from the tank, put it into the tub with soapy water and as I pull the film off of the reel, I remove the remjet from the backside of the film with either my fingers or (preferably) a soft brush. Due to the soap in the water, the remjet remains very soft and removes easily.
The one thing to look out for is to only unroll the film in small sections (one frame at a time) and completely remove the remjet before proceeding. If I let the film with the remjet still on it unwind into the tub, it’ll roll back up on itself and the remjet that’s still on the backside of the film will imprint on the emulsion side. This tends to show up on prints or scans as white smears and specks, often with the sprocket hole pattern clearly visible:
If this happens, not to worry. One nice thing about these Vision3 films is that the emulsion is pretty well hardened and robust. This means that if some remjet ends up on the emulsion side of the film, it can be soaked in soapy water and the remjet can then be removed by gently rubbing the film (yes, the emulsion side!) between thumb and index finger. Be sure to wash hands properly beforehand so that no sand etc. is on your hands, as this will scratch the emulsion. With clean and soft hands and a gentle touch, there will be no damage to the emulsion when cleaning it this way.
This can even be done if the film has already been dried, cut and stored away. Just put it back into a tub of soapy water and rub off the offending remjet remnants. I prefer to use lukewarm water for this purpose because it helps to soften the remjet – and also because it’s a lot nicer to work in a bath of warm water, especially in winter!
After removing the remjet with soapy water, I take the film and wash it under a running tap until all traces of soap are removed. I do this by holding the film on both ends and see-sawing it underneath the running tap, alternating between both sides of the film (emulsion-side and backside). I then hang up to dry from a clothes line with a weight at the bottom, and gently wipe off water from the backside with a clean cloth or a piece of paper tissue to prevent drying marks.
With a bit of practice, it’s fairly easy to get perfectly clean, flat and beautiful negatives this way. While it may sound like some work, it only takes about 5-10 minutes per roll, so it doesn’t add all that much time on top of regular color processing.