Bob D659 does, indeed, bring up a valid point in that the development process does release gas. But, so does carbonated soda. That is why there had to be a truly leak proof container made for soda. Enough did not 'complain' that the same should have been done for 'mere' darkroom nuts.
And, Ken Nadvornick, there is a valid point here about the desirability of using a material such a stainless steel that AIDS in conducting temperature (ie, water bath). But, still, there are some who would like a truly leak free tank.
And Gerald C Koch, I am not saying that you are wrong with your SS tank with plastic top being entirely leak free, but I would like to put it dry upon a towel, without your water bath, and see it stay dry. I have my doubts but it might be as you say. In a water bath you would never notice a leak. And you could not prove this by merely putting food coloring in water to see if any color came out into the water bath. As I just confirmed Bob D659: there is a pressure build up that 'forces' leaks in the development process. - David Lyga
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.
It occurs to me that very few in the beverage bottling industry see much need for a bottle that is both light tight and enables rapid dumping and filling of liquids.
So I'm not sure that is a great source of comparison.
They also need to open and close only about 5-6 times. And, they only have one cap. A developing tank has two.
Originally Posted by MattKing
I would like to see a stainless tank with deep screw top threads, on both lids. Kinda like my martini shaker...:)
Here's another brand sold by B&H:
Originally Posted by paladin1420
I don't know if this is really the same as the Samigon posted earlier.
The price is $2 higher, so it must be better. :)
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.
Originally Posted by bobwysiwyg
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.
Originally Posted by Ken Nadvornick
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.