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.
Originally Posted by octofish
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 :D
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.
I suppose O-ring gaskets would not work without a proper groove on the lid and on the tank.
Originally Posted by hoffy
Originally Posted by David Lyga
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.
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