View Full Version : A Better Mousetrap - DIY Developing Tubes (Part 1)

25-Aug-2012, 20:59
As I'm always looking for solutions to non-existent problems, so I figured I'd spend a couple of hours in the shop to see if I could cobble up a couple of daylight developing tubes.

I came up with two prototypes. One with a screw on end cap, the other with a push on cap.

The tubes are basically the same:

5-3/4-inch length of 1-1/2-inch ABS pipe.
Push on end cap with hole drilled in the center for a rubber stopper.
Two disks made form 2mm nylon plastic with 1/2-inch fill/drain holes. (Sanded to minimize any reflections)
3-mm spacer cut from the 1-1/2 in ABS pipe

Push on end cap (painted black)


1-1/2" ABS threaded end cap and adapter

The disks are stacked (separated by the 3mm spacer) at one end, with the fill/drain holes on opposite sides creating the light trap. The ABS cap is glued over the two disks, sealing them in place.

Once the film loaded in the dark and the tube sealed, chemistry is added/drained at the stopper end.

Total cost:
$7.50 for the threaded cap assembly prototype
$5.00 for the push on cap assembly prototype

Both work equally fine.

25-Aug-2012, 21:00
Final assemblies.

Peter De Smidt
25-Aug-2012, 21:56
Nice work!

25-Aug-2012, 22:36
Good job.

I have planning on doing something similar, but with 2 1/2" ABS or better yet a schedule 80 PVC. This would be to develop 4X5 and 5X7 film.

I have not been able to find the threaded ABS caps like you used. That is one reason I was looking to use schedule 80 PVC. I could just purchase a 5 or 6" inch threaded nipple.

How much chemicals are you using to develop a sheet? Are you using a rotating base or spinning them in water like a BTZS tube?


25-Aug-2012, 22:47
I had the same problem. So in the end, I made my own threaded cap. It's a modified coupling that I glued a disk into and sealed with a bead of silicone. However if you're in the states, Grainger sells a suitable cap online.

BTW, 1-1/2 inch uses less chemistry, about 2-ozs per sheet, spun in water like the BTZS.

25-Aug-2012, 22:50
The BTZS tubes are welding rod tubes.

Why reinvent the tube?

25-Aug-2012, 22:51
I have no idea where to procure welding rod tubes, without the rods? Plus, rod tubes do not lend themelves well to light traps.

25-Aug-2012, 22:58
Ebay or Amazon.

Search welding rod 'cannister'. They are blue or yellow, not black. So lose style points there.

Rod Guard is a trade name.

25-Aug-2012, 23:01
I wonder if they're translucent and need to be coated to keep the light out.

25-Aug-2012, 23:10
I was wrong

They do make them black.


I don't know if they are light tight or not. Never used them. Seemed like too much work to me.

25-Aug-2012, 23:12
I think I may try to use a rod guard and see if I can build a light trap into the cap. Plenty of depth to accommodate the required disks. It then comes down to suitable adhesives.

26-Aug-2012, 08:54

Why build a light trap?

Just use an extra cap to hold the developer until you're ready to develop, as in the BTZS method. Or just preload the cap with developer and keep the tube end up until you start agitation.

26-Aug-2012, 11:21
The only advantage, and it's pretty specific to my situation, is that I don't have a darkroom. I have to load film in a small closet which I share with my wardrobe. So, I prefer to keep the chemistry out of the closet. The light trap also ensures that after film loading, all other steps are light-tight.

The disadvantage of the light-trap is that it takes about 10-seconds to pour the chemicals in. If I use more than 1 tube, I need to take the accumulated time into consideration.

26-Aug-2012, 15:29
The BTZS tubes are welding rod tubes.

Why reinvent the tube?


The only reason that I don't use the welding rod/electrode tubes, is that they are too long for 4X5 film. If I didn't have BTZS tubes for my 8X10 film, I would purchase some. I have used the 8X10 BTZS tubes to develop 5X7 and 4X5, but it seems like an overkill.

I saw some welding rod/electrode tubes at Harbor Freight. They were red plastic with a handle. The handle could easily be cut off. What is nice about the welding rod tubes, is that they are water tight, but just too long.


26-Aug-2012, 16:07
Took this test shot this morning (Ilford-Delta 100). Developed it upon my return home (Kodak D76 chemistry). Scanned on my Epson V750 with no post-scanning alterations. Tube seems to be working fine. Sorry about the small jpg.

26-Aug-2012, 17:04
Nice job. So these are 1 negative per tube? I'd love a sort of home-made jobo tank where I could do 10 5x7s at once. Not sure that one is going to happen, but that's my dream.

26-Aug-2012, 17:13
Yup, 1 negative per tube.