Tanks: they leak and they lose temperature. WHY?

bobwysiwyg said:

I use the much maligned Combiplan with no leaks. I have say though, initially I did until I figured out the issue. You press the lid on thinking it is tight and secure, dribbles persisted. Because the lid is softer rubber it "grabs" a bit and doesn't really secure, water tight unless you apply a good deal of pressure all the way around. I do it by pressing the tank bottom to my chest, then working my fingers around the rim firmly press the lid against the rim of the tank. No leaks since and I do inversion agitation.

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I do the same but I press the tank on a table and I press with my weight on it. I really press hard checking all the rim is well pressed. The "click" is not enough as experience shows.

That work but a thermic flask design would probably be better for inversion use. I use open tanks (Jobo with "lift") so I don't think I would have a substantial advantage in using such a design.

I would advice against trying with a thermic flask as developing produces gases and thermic flasks don't have a vent they could, who knows, "explode".

The problem with JOBO tanks popping the lid off can be cured by using a red hot needle to piece the top cap. This allows the release of the gas pressure caused by mixing the developer and blix. If you use the inversion technique it is a simple matter of putting a small strip of adhesive tape over the hole, or even simpler, use your index finger. With the cap intact, I have never had a jobo tank leak. I also have a quite old 120/35mm Jobo tank with a screw top and the red top is of a different design but this has the hole already made.

I also have tanks made by Durst (Centre loading plastic) and unnamed stainless and non of these leak , - I must be unique, but when they are in use, they stand in a bath of warm water. So if there was a leak it may go un-noticed, but mine don't anyway.

eddie said (concerning soda bottles): "They also need to open and close only about 5-6 times."

I take issue with that inferred lack of durability. I regularly use these same bottles for storing developer, stop, and fixer and have used the same bottles for YEARS. The caps never wear out and the tightness of fit remains intact. - David Lyga

I use SS tanks for the reason of being able to use Hewes reels, because they are unbelievably good. A pleasant side effect was/is what you're describing - thermal transfer from surrounding water bath to temper processing solutions to perfection. I use very little water by simply dipping my thermometer into the water bath, and pour in small amounts of warm water as the temperature drops more than a half degree below my 70 degree processing temp. Works swimmingly well.

And, with the plastic lid my stainless steel tanks do not leak.

Ken Nadvornick said:

Single-walled stainless steel tanks are preferred precisely because of that thermally conductive property. That very characteristic is what makes precision temperature control in a tightly maintained water bath possible. Very low thermal inertia. Contained liquids respond very quickly to changes in external water bath temperatures.

In my own case I maintain water bath temperatures using a Hass Intellifaucet K250. Marvelous temperature control possible using this precision tool. In the winter I often set the Intellifaucet to, say, 68.4F to counteract the slight loss of solution temperatures resulting from the colder darkroom ambient air temperature. Single-walled stainless is what makes this possible.

What needs to be insulated is not the stainless steel processing tank (or tanks). It's the container holding the water bath in which they sit. That's the common reference point that you don't want to drift. I would never use plastic processing tanks. Too difficult to precisely adjust. Especially for color.

This particular behavior isn't a bug. It's a feature.

Ken

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One note about the Jobo tank lids; for C41 processing where one expects some expansion from the tank the red lids are designed to be pushed, or popped, inwards before being put on the tank. The gas produced during processing then pops the centre of the lid back out again whether using rotation or inversion agitation.

For the Paterson System-4 tanks with the one-piece "Tupperware" style lid I just fart the lid, in the same way that one does during putting it on initially, except in between the inversions. In that way the pressure is prevented from building up, note that nitrile gloves are a good idea for this as there can be splashes depending on the pressure released.

octofish said:

Not sure that a well insulated tank would be that useful. Unless you temper it very accurately - which is a pain to do - you will get a temperature change when you put chems in anyway. Tempering will be impossible from the outside (it's not even all that feasible using a normal plastic tank - takes too long), which pretty much means you need to prewet whether you want to or not.

The other option is estimating the expected temperature change, which is necessarily uncertain. You can always measure inside the tank with a thermometer to work out where you are, but then if you are wrong, how do you get the tank temperature to where it needs to be, if the tank is well insulated? A water bath will be ineffective.

Also I believe some proceses (fixing?) result in a bit of a temperature change by their nature, in which case you're stuck where you end up as a result of that. Could be wrong about that though.

Of course, this is all if you care about that level of precision. If you don't, then a plastic tank is pretty much good enough anyway.

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I think that an insulated tank would be so that you would pour in developer at 39C and expect it to stay above 38C long enough to process a roll of film. One of the issues, the developing tanks we know and love, were designed for B&W film, where you usually used room temperature, measured the temperature of the chems, and used a time that matched. If you were to design a tank today for colour use, it would be designed quite differently.

1) It would be able to maintain temperature for the duration of the process.
2) It would not leak, for a steel tank with a steel lid, this is actually easy, put a neoprene ring in the lid, so that when the lid and top of the tank meet, the neoprene fills any voids.
3) Would have a plastic top cap, on a spring over the filler hole. When filling and emptying the tank, you hold the cap open, otherwise the spring holds it closed. If pressure builds, the pressure pushes the cap up, and releases the pressure. We add a small weighted latch, so that when the tank is not sitting flat, the cap is held closed. You can still use inversion agitation, during the 5-10 seconds your agitating the tank, pressure isn't going to build enough, that during the 50 seconds it's sitting flat, it can't be released. Of course when pressure is released, you might burp a little chemical, but you can wipe that off with some paper towel.

The fixing process, could change the temperature slightly, fixing, is not that critical temperature wise, it's development where temperatures are critical.

So, after developing some film last night and then cleaning up the fix stains on the laundry floor this morning, I too have been wondering about leaky patterson tanks.

So, this morning, I am going to try 3 wraps of teflon thread tape on the threads and see how that goes.

The other though (& I am kind of suprised that one has mentioned it) is to use a standard industrial variety O ring in the lid of the tank. Surely, that will help with sealing, or am I missing something?

I think this may be the reason that some of us are surprised that so many have problems with Paterson tanks. The screw top versions (System III) were replaced far more than 25 years ago with the tupperware-lid style (System-IV). The sealing washers on the ancient tanks stand very little chance of still being pliable enough to work, if indeed they are still present - it was a grey, slide-in sort of ring if I remember rightly.

My advice would be to find the newer tank version, but don't forget to keep the reel(s) from the old one as a spare because they are the same size. The new reels have mouldings to grip the central-core of the light trap so if the old reels slide around use an elastic band, or an original plastic clip from the old tank, to keep them in place.

Buy replacement tanks? You jest

Actually, I have some relatively new tanks that are like the old Patterson ones. I also have a lot of older tanks that were given to me. I am sure its not going to be that difficult to stop the leaks. (its only been recently that they have leaked more then usual).

My thread tape trick worked fine. Yes, I got a bit of leakage from the top cover during the stop and fix stage, but that was more residual fluid from the pour out then from agitation.

hoffy said:

The other though (& I am kind of suprised that one has mentioned it) is to use a standard industrial variety O ring in the lid of the tank. Surely, that will help with sealing, or am I missing something?

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I suppose O-ring gaskets would not work without a proper groove on the lid and on the tank.

David Lyga said:

Coca-Cola can make a leak proof bottle for about 2 cents. So can multitudes of other manufacturers. Why cannot there be a film tank that absolutely, really and truly does not leak even one drop?

And one that holds temperature like a Thermos?

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Let's see:
Stainless steel tanks with steel lid: leaks. Why? No gasket. Not much, but it does. No big deal.
Stainless steel tank with rubber lid: No leak.
Patterson tank, plastic/rubber lid: No leak.
Jobo tanks, using plastic/rubber lid: No leak.
Jobo tanks, using cog lids: No leaks when attached to lift unit.

Heat:
Tanks go into tempered water bath. No problems.

If you want to develop your film in a Coca-Cola bottle, remember to keep the lights off. If you want to develop your film in an insulated jug, which is just fine IMHO, you'll need to switch off the lights when changing chemicals.

And remember, the Combiplan is far superior to the Yankee tank, which isn't sealable at all.

A bit of a daft question really. Coke cans don't leak because they are for a one off task. Just try try-sealing one!!!!

The only Dev tank I ever had leak was an ancient one 40-50 yrs ago where the only agitation was by a rotary process with a rod through the top and when it was upright. All my current tanks I use, ( 4 x Jobo [35mm & 120] 2 x Durst 35mm and 1 stainless 35mm) never leak provided the lids are put on properly. All it takes is a bit of care.

As for losing temperiture, ANYTHING will cool down if left in a cooler place than where it was when it was first heated up