Testing processing chemicals?
Posted 30 November 2008 - 05:19 AM
Posted 30 November 2008 - 06:28 AM
As for the liquid, it really does depend what it is. Concentrate will last longer than working strength, fixer longer than dev. As long as fixer still smells acid, I'd be happy with it, but if the developer is anything deeper in colour that a pale brown, it's probably oxidised.
Posted 30 November 2008 - 01:09 PM
Even with all of Kodak's admonishments to maintain the quality of chemicals, we kept our chemicals in the worst conditions, left them in the tanks way, way too long and still got some really fine results back 28 years ago at Ole Miss's color reversal lab. Crazy.
Posted 01 December 2008 - 04:14 AM
Edited by James Steven Beverly, 01 December 2008 - 04:19 AM.
Posted 01 December 2008 - 09:17 PM
The Rapid style of Fixer is generaly supplied as a liquid. I belive it is hard to get ammounium thirosulphite (Sure I got a few letters wrong) to go into solution so they provide it as a liquid. When it goes bad, it has some sulpher come out of the solution so it turns yellow and and starts to smell like sulpher. Dry Plain Hypo is quite stable as a crystal s long as you keep it dry.
I think the liquid is fixer, I'll have to check. it DOES get hotter than Hell ...
. I thought you could mix up fixer and developer from dry chemicals, am I wrong?
Most developers for B&W are supplied as a powder, or a liquid. the weak link in most of them is the deveoping agent itself. (Metol, Phenendone or Hydroquinone) which can turn dark if it can get any air. 40 yaers ago the dry stuff came in a metal can you had to open with a pull tab or sometimes a can opener to keep out the air. These days they use a paper or plastic bag. With a few exceptions like "Rodinol" developers that change colour have gone bad.
I am not sure of the stability of the colour formulas, but it is probaly less than the B&W ones.
Posted 01 December 2008 - 10:12 PM
Posted 03 December 2008 - 04:14 AM
The easiest way to check fixer is to make up a small quantity and stick a bit of raw stock in it, agitate it about and see how long it takes to clear. Fixing times are usually twice the clearing time. So if you know what the fixing time is for the process you are running you can see if it is any good. Make sure the temperature is near enough as that will affect the fixing time.
Ammonium Thiosulphate ( I googled, 'cause i can't spell it either) BUT close enough
You can do a similar thing for B/W developers and stick a bit of raw stock into the developer, agitate it for about the correct development time and make sure the film has gone good and black. You do this in the light.