Developing Tank [Construction and Adventure]

Lloyd Erlick.
July 26, 1996

A very strong, durable, practically impact-proof developing tank can be made by the darkroom handyman from ABS plastic pipe.

ABS is acrylic-butadiene-styrene, the plastic used to make drain-waste-vent plumbing pipe. The pipe under your toilet is very likely made of ABS, and has probably taken way more shit than you will ever hand your developing tank!

To build a developing tank, use 4 inch pipe. The slightly larger developing spirals that adjust from 35 mm to 120 format fit comfortably inside this pipe. I have been using the Jobo version of this type of spiral for many years, and they fit perfectly, as do the Paterson spirals. Stainless steel reels are slightly smaller, but they fit equally conveniently. The 120 size stainless steel reels are too large; if you can afford a bunch of these you're probably not interested in gluing up plastic for a home-brew tank anyway!

Four inch plumbing pipe is four inches inside diameter. The wall of the pipe is quite thick, not a factor in our calculations, but definitely a major factor in durability. This type of pipe will not flex in your hands, and it will not crack under the sort of impacts it is likely to suffer in normal use. Just be sure never to let your hand become the impact-absorber between the tank and the edge of your sink, or you'll find out how rock-solid it is!

The cheapest way to buy ABS pipe is in ten foot whole-piece lengths. In July 1996 I paid C$ 35.00 for one, although shopping around plumbing and building material suppliers may yield a better price. There is also the possibility of finding a scrap at a building site, or in the garbage. Photographers should never overlook the possibilities of dumpsters and garbage in general, especially in the printing industry districts of large cities.

A description of parts and materials is at the end of this article.

Working with this type of plastic is easy. It cuts very well with a common hack saw. The end of the pipe need not be cut at a perfect right angle, because the couplings are quite deep. A perfect right angle cut is easy to do, however: wrap a piece of paper [a sheet of newsprint is good] around the pipe, and line up its edges. The lined up edge will indicate a perfect circumference of the pipe. Make a series of marks and follow them slowly and carefully with the hack saw. It's easier to do than write about! The cuts are always rough, with lots of plastic burr. Ordinary sandpaper, coarse grit, is all you need to take care of this. Wear work gloves!

I have found a 13 or 14 inch length of pipe works well. The coupling and other fittings add length, which turns into depth when we start calling it a developing tank. The resulting volume is a bit over a US gallon, just right for half a gallon of D76 stock diluted 1:1. Four spirals, each holding two rolls of 120 film, fit comfortably on their holder. D76 is rated at a capacity of 16 rolls per gallon of stock. Thus a tank that holds eight rolls and a gallon of D76 at 1:1 dilution is fine. Most developers will have dilutions and capacities not far from convenience in this type of tank.

For 35 mm film, eight spirals can be used. The depth of the tank is adequate; in fact, one is tempted to put in even more. Whenever I've done that, developer exhaustion effects have been completely absent. I wonder if film and developer manufacturers rate their capacities for film that is uniformly exposed to maximum density?

A single tank is adequate, but it demands handling and pouring solutions in the dark when the lid is removed. I just work in the dark, with seven tanks arranged in sequence in my sink. I use a separate tank for each of: plain water presoak, developer, first rinse, second rinse, fix, rinse, and hypo clearing agent. The tall, narrow shape of these tanks makes it easy to completely submerge the spirals with the minimum, but adequate, amount of water or chemistry. Of course, when the fix step is finished the lights can come on, but since that tank has a closure, I turn the lights on at the start if fixing. This gives me time to get my tap water flowing at proper wash temperature, and to dump one of my rinse tanks and get it refilled for rinse after hypo clearing agent. I also use the time to dump and rinse all the used tanks, not forgetting all the while to keep the fix agitating. Mr. Kodak reminds us to use continuous agitation in the fix! I prefer not to lift and invert these tanks; they're too heavy. I lay them down in the sink gently, roll them around, lift the bottom up, turn them back right end up. Don't worry about letting them stand for a moment or two. The liquid inside is swirling around pretty well. Just don't let your mind wander!

This system has advantages for me. First and foremost, it makes for a half hour of peace and calm in the dark. I can sit watching the timer, lifting and lowering the film, thinking my own thoughts. No heavy weights in liquid form are wrestled in darkness. The timing in each solution can be exact: the pouring time of a gallon of liquid is eliminated. Agitation is effortless: no lifting, no mid-air inversions. The fix tank and hypo clearing agent tank have screw cap closures so I can store these solutions in their tanks. They are never poured back and forth. A piece of tape on the outside of the tank is all I need to keep a usage tally for each solution. The rinse tanks have no closure [cheaper!] and are superior to random shape containers or buckets for this purpose because:

They fit in the styrofoam picnic basket I set all my tanks into! It comes complete with water filling and aquarium heater adjusted to 21 degrees Celsius. All my solutions and tanks can be temperature stabilized more or less permanently, or at least overnight. The styro basket has enough room for developer stock bottle and distilled water container. The aquarium heater draws only forty watts, so it's way cheaper than keeping my whole darkroom at 21C in the winter. And it's made to be used around water. (I never expose it to chemistry.) These picnic baskets are so cheap I use a second one as a cover.

Because I was a little over-enthusiastic when I went out to buy materials for my tanks, I ended up with a wonderful luxury item: an extra tank. I have found it is a perfect holding container when I load rolls of film onto their developing spirals. I keep this tank dry permanently, and the lid carefully at hand when loading film in case I'm interrupted. A bonus discovery: leaving the film loaded on spirals, sealed in this tank, has no ill effect for at least forty-eight hours. That's the longest I've ever left it before developing.

Parts and Materials:

Besides the pipe, certain fittings will be necessary.

Couplings - to join other parts to the plain pipe.

Screw-cap fitting - sometimes called a cleanout fitting. It has internal threads and joins to the pipe with a coupling. It allows a full-diameter screw cap to attach to the pipe.

End cap - the hard-to-find essential part! I'll have to go on at length a bit here. There are various ways to make the 'bottom' of the tank. Usually one has to hunt through the parts bins at the hardware/plumbing supply to find some sort of closure for the pipe. The end cap is sometimes called a 'pressure test cap' and is made to block the end of the pipe. Be sure to get one made of ABS; sometimes they are made of flexible polyethylene, which is not as strong as we require, and the glue does not adhere well. Sometimes you will be able to find a 'flange' with a flat surface to close the pipe. The rotating part of the flange can easily be cut off later.

Glue - use the glue sold for the purpose at the place you get the ABS parts. It is usually color-coded yellow, and the can should state 'yellow.' In any case, make sure it is made for ABS pipe. A small can goes a surprising distance, and is fairly cheap. Use it outdoors if possible: the volatiles are disgusting! Adequate ventilation is essential; plumbing contractors send their assistants into confined spaces under toilets to work with it.

Cleaner - sold to clean the plastic before gluing it up. It is not necessary, so don't buy it, even though it's presented as an essential. It is raw, pure volatile solvents, and you should give up photography before breathing this stuff. Just make sure the plastic parts are free of grease and dust before gluing.

Sandpaper [coarse] - the plain kind is adequate, but waterproof, or 'sandcloth' or Emery paper are more durable. If you plan to make several tanks, get the sandcloth used by plumbers.

Copyright Lloyd Erlick. All rights reserved.