i've never used anything but kodak rapid fix, and i've always been somewhat disappointed that it gets exausted--according to the hypo-check solution i use to test for silver saturation--way before my developer or stop bath gets exausted. do any of the other types and/or brands of fixer last longer?

-- brad daly (bwdaly@hiwaay.net), March 12, 2000

Answers

It is best to use a two bath fix. You mix the fixer to film strength (follow the directions for using it for film). Then use two trays.

You fix in the first tray for 30 seconds. Then the second tray for 30 seconds. When the fixer in the first tray becomes exhausted, then move the second tray to the first position, and the put a tray of new fixer for the second.

Fixer mainly becomes exhausted due to excessive silver build up, not chemcial exhaustion. You could possibly use an electrolytic silver recovery unit in your fixer to remove the silver as it is removed from the prints. But I can't see that it is worth the trouble.

If cost is a problem, just buy cheaper fixer, like Sprint.

-- Terry Carraway (TCarraway@compuserve.com), March 12, 2000.

I could well be wrong, but I think that recovering silver from the fixer won't itself restore its usefulness (because the inactivity is due to the presence of the halogen, or something). But maybe the silver recovery also removes the halogen?

Anyhow, if your fixer stops working before your developer, you could just use more fixer. Certainly, two-bath would be even better.

-- Alan Gibson (Alan@snibgo.com), March 15, 2000.

Alan,

I will have to try this.

The fixer test kits test for silver buildup in the fixer. Next time I exhaust some fixer, I will silver recover it, and see if it works.

-- Terry Carraway (TCarraway@compuserve.com), March 16, 2000.

Terry, this is an area I have some familiarity with. Alan is correct; in some way iodide ion in solution drastically slows down the rate of fixation (clearing of film, etc.). At least some (many?) modern films seem to contain a fair amount of silver iodide. So although you could electroplate out a lot of the silver and get it down to acceptable levels, the fixing time will likely still increase and limit the usefulness of the idea.

Paper, by comparison, typically is real low on AgI, so the idea ought to work here. It's probably still not economical for a home darkroom, though.

-- Bill C (bcarriel@cpicorp.com), March 16, 2000.

Bill,

Thanks for the info. I will still try the experiment. Porter's (www.porters.com) has a silver recovery setup for $35. It is an electrolytic silver recovery process.

It should be interesting.

-- Terry Carraway (TCarraway@compuserve.com), March 17, 2000.

I just got the Porter's Silver Magnet in. The directions do talk about using the device to increase the fixer life.

As Bill pointed out, you have to be careful of going too far with the silver recovery to the point of removing other ions. The directions talk about the color of the recovered material changing from white to dark as you go to far, as well as the fixer itself turning dark.

It looks like this may be a way to increase fixer life. Whether it is worth the trouble or not is something else.

-- Terry Carraway (TCarraway@compuserve.com), March 22, 2000.