PVC development tubes for sheet film

Warning: again a total lack of originality on my part. The upshot is that apparently I don’t suffer too badly from the not invented here syndrome because I proudly stole reproduced this idea from Tim Layton whom in turn was inspired by Phil Davis and his “Beyond The Zone System” approach. The whole idea is essentially just a hollow tube with two end caps in which you put a single sheet of film, fill ‘er up with developer and agitate in whichever way you fancy. This could be a fancy water bath agitator like in the official BTZS approach, or, as in my case, simply turning the tube over and over like a regular daylight tank, or rolling it on a counter top.

If you want to get this right in a hassle-free way and just throw some money at the problem, get the actual product here. I generally don’t, because I tend to tinker, so I see if I can DIY something together. Just like Tim did, and my ‘solution’ is pretty much an exact copy of his with some bells and whistles added to it.

What I think Tim’s solution and mine have in common, and the official BTZS tubes don’t, is that my tubes don’t wobble if you roll them. The original BTZS tubes are wider in the center section and as a result, if you put them in a tray with a water jacket and then rock that tray, the tubes will wobble about a bit. This makes for perfectly random agitation of the developer inside. Nifty, but as far as I can tell so far, not really necessary. And if you prefer rolling the tubes on a counter top, it’s actually less convenient to have the original BTZS ones precisely because they wobble about.

First, a little background to why even bother with this. After all, I have a Jobo 2500 series tank that conveniently fits 6 sheets of 4×5 in a 2509N reel and I can just plop that onto my very old and filthy CPE2 and be done with it. So far, so good, you’d say. And indeed, for color it’s pretty much the best/only thing I’ve got. However, for B&W, it’s not the ultimately solution, for two notable reasons:

1: The 2509N reel, despite its black plastic flaps on the sides, does not always give me perfectly even development. More often than not, there are narrow minus-density bands along the long sides of the sheets. The rest of the frame will be perfectly fine, but I tend to lose the edges to unevenness. So far, I have not been able to solve this with the Jobo system. The problem was worse with the old 2509 (non-N) reel that did not have the black flaps.

Jobo 2509 reels: newer 2509N to the left, the older plain 2509 to the right. Note the black flaps on the 2509N which mount onto the reel where the short ends of the 4×5″ sheets are. This is supposed to improve flow patterns across the sheets, and indeed it does help quite a bit. But it’s not a guarantee yet for perfectly even development.

2: Despite being critical of reduced agitation schemes and outright dismissive of stand development, there’s an appeal to the core ideas put forth by people like Steve Sherman. I’m currently interested in optimizing adjacency effects to improve acutance of contact-printed sheet film, in particular for carbon transfer printing. I have to be honest in that I don’t expect miracles from this, but I won’t dismiss it out of hand before even trying. While the Jobo tank could be used for this, I’d prefer to have something in which I can develop a single sheet of film at a time using a somewhat sane volume of developer. Doing that in a 2500 tank would take something like 1.5 liters of developer, which seems excessive to me.

3: My 2500 tank works quite nicely for 4×5, but for 8×10 I’d have to resort to something else. I must have at least one paper drum extension for the 2500 series somewhere, but I’m not quite sure where it ended up in our new home. Also, it would still take an even more excessive amount of chemistry to do things like semi-stand or reduced agitation with a paper drum. No cigar!

Because of all of the above, I thought it would be an interesting idea to see if I could cobble together something like the BTZS tubes from hardware stuff, just like Tim Layton did. Skipping over the sawing, grinding, gluing, CAD-designing, taping, cursing, etc. etc., here’s the end result:

DIY sheet film development tubes. Materials: PVC drain tubing and screw-type end caps, 3D-printed light-proofing end caps/shrouds, lots of black duct tape, a dash of black acrylic paint, and some tin and copper foil for good measure. That should do it!

The central idea is quite straightforward: a piece of PVC drainage tubing of an appropriate size with two screw-type end caps. Ok, would be nice if that was the end of it, but it wasn’t. Because with that skeletal setup, I managed this:

Snapshot of 4×5″ negative on makeshift light table. Notice the dark band at 1/10, 1/3 and another one at 2/3. The dark circles/bubbles are a light table artifact; ignore them.

Ok, not OK. Dark bands all over the place. Turns out they aligned quite nicely to the thinner parts of the PVC construction. In other words: I had reproduced the problem that Tim Layton also observed, that drainage PVC is not light proof. Of course, he used the white stuff that’s more common in the US, and I had hoped that the heavy-duty grey stuff that’s common over here would fare better, but I guess it doesn’t. So I had to patch things up, which I did in the following way:

1: Apply bands of copper foil or (cheaper, just as good) tinfoil over the thin parts of the walls. Especially the center section of the tubes is prone to passing some light through because this is where there’s just a single layer of PVC. Even at around 3mm thickness, it’s not perfectly opaque. Some duct tape goes over the metal foil for protection. The black duct tape also adds some additional light shielding so it won’t hurt.

2: I designed and printed some snugly-fitting shrouds over the end caps. I mainly did this because at least part of the problem appeared to be the threads on the PVC tube being slightly thinner than the smooth tube itself. Since it’s a screw thread, paint etc. will scrape off (I applied some and indeed, it does flake off with use, as expected) and/or interfere with the screw action. I decided having a shroud fitting fairly tightly over the tube would cast a very deep shadow on the exposed part of the threads, reducing the problem. Fortunately, this proves to be quite effective so far. I put it together in Fusion 360 based on some measurements of the PVC end caps and printed it using black opaque PETG filament. (Man, those things took long to print!)

End cap shrouds for the development tubes. The vertical slots in the larger shroud fit snugly over the protrusions of the PVC screw type end cap. The narrow section of the shroud fits right over the exposed part of the threads when the tube is closed. The wider section at the top is to make it easier to fit the cap in the dark. The disc fits over the end of the cap and is glued in place for additional light proofing and, alright, insofar as possible with this contraption, aesthetics.

The end result looks like the first image above; here’s some more pics from different angles:

8×10 tube with end caps and shrouds. Notice the rubber rings in the caps (they’re factory-supplied) which make for a nearly perfect seal. There’s a few drops coming out during development, but nothing problematic.
Inside of the 8×10 tube; it took some grinding and polishing with 800 grit sandpaper to get everything smooth enough not to scratch the back side of the film. Emulsion goes inside, of course, so it never touches the walls.
End cap close up; the grey PVC is the store-bought part, the black rubber ring inside the lid comes with it. The black outer shroud is the printed part. Notice how the protrusions on the PVC lid fit snugly into the printed shroud; quite happy with how that turned out. It’s a perfect friction fit requiring no glue to keep in place, and it withstands the lateral force of screwing the lid this way!
I damaged the duct tape a bit on the 4×5 tube; it now shows the copper tape underneath that offers perfect light proofing.
Inserting film is straightforward; roll it up, squeeze together a bit and slide it right in. Then push it all the way to the bottom.
The film fits snugly inside the 4×5″ tube; notice the few mm’s of clearance between the long edges of the film. Turns out 40mm diameter PVC pipe is a perfect fit!

Does it work? Yes, yes it does! As evidenced by a comparison picture of the earlier mess-up:

Unevenness problems on the left due to light fogging through the bare PVC. To the right, the improved tube version with additional light proofing. The higher density diagonal cast in the upper right section and the vertical gradient are in fact the actual lighting of the background. Development on this negative is perfectly good enough for my purposes; other negatives including 8×10’s show no density problems in skies etc.

Here’s the 8×10 version in action:

Rolling the 8×10″ tube on the counter. I usually put a towel beneath it to reduce the noise of rolling a heavy and hard plastic tube against a hard countertop. Sounds a bit like a streetcar making its way across the room! Because I designed the tubes symmetrically, they roll very easily.
Film inside the tube after development and stop, just before the fixer went in. It usually shifts a little bit inside the tube, but as long as the filling volume is sufficient, this does not cause any trouble.
Extraction of the film is the same as insertion. Care is needed because the film scratches easily when wet, especially Fomapan 100 which I used here.
I do the final wash in a tray. I generally use plastic storage boxes because I like the high walls that prevent splattering all over the place. Because the film tends to stick to the tube wall in some places, anti-halation dyes on the backside of the film don’t always rinse out well with the film inside the tube. A wash in a tray fixes this.

The 8×10″example above was shot on Fomapan 100, exposed at around E.I. 50-80 or so (allowing for reciprocity failure), developed in Pyrocat HD 7.5ml + 7.5ml + 1000ml for 45 minutes with a few seconds of agitation by rolling the tube on the countertop every 5 minutes for the entire duration of development. This yields a fairly beefy negative that’s just nice for printing on 1.5% pigment concentration carbon tissue. I’ll probably increase development further in the future because this is about the lowest contrast negative that prints easily; a little more density won’t hurt.

What’s next? I’m playing with the thought of making a roller base with a little motor so I can do continuous agitation development while keeping my hands free. As said before, I doubt the reduced agitation approach makes all that much visible difference in my negatives; so far, nothing really stands out, but I have yet to do some proper side-by-side testing with identical negatives. However, I foresee that I will go back to continuous agitation at some point, and then it would be nice to have a handsfree option to process sheet film one by one. And if all else fails, I can go back to trays, as I did before, because what worked back in the 1800s still works just fine today. As long as you don’t mind standing around in the dark rocking a tray, and I have to admit that does get tedious sometimes.

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