View Full Version : Can you overfix with TF4?

25-Jun-2006, 20:31
I'd like to use Formulary's TF4 alkaline fix in an old Phototherm Sidecick to develop FP4+ 4x5 sheets. The Sidekick is set to fix the film for seven minutes. Given the constant agitation that the machine this will probably be about twice the time that's recommended. Now, I know their are dangers inherent to overfixing with a acid fix, but I wonder what risk I take by overfixing with an alkaline fix. Does anyone have any experience with this?

David A. Goldfarb
25-Jun-2006, 21:03
There isn't much risk of overfixing with TF-4, but 7 minutes is way more than you need for FP-4+. With constant agitation you might only need 1-2 minutes.

25-Jun-2006, 21:22
True, but it will cost me $100 to get another "process" added to my Phototherm. Other than the seven minutes of fixing, the process they have seems fine. It uses a water wash for stop, which is recommended when you use constant agitation and the wash is fine.

Formular says that you should never overfix, but then they advertises TF-4 as being safe in the event you overfix, so ... .

I wonder if I just diluted the TF-4 if that would be better.

John Berry
26-Jun-2006, 00:51
When developing by inspection I have had some negs in for that long and couldn't tell any difference from the ones that I do at my normal 3 min.

John Bowen
26-Jun-2006, 04:09
Formulary recommends a longer fix (say 6 minutes) in order to clear out the "pink" dye with Kodak Tmax400 with TF-4.

Henry Ambrose
26-Jun-2006, 05:39
I routinely fix for 5-6 minutes using TF4. I've not had any problems as all. I don't think 7 minutes will be a problem for you. Not even close to a problem.

Jim MacKenzie
26-Jun-2006, 07:52
Overfixing is a problem, but alkaline fixes cause less harm than acid ones and seven minutes is not so ridiculously long that it should be a problem.

You might want to extend the wash to be sure you have all the fixing byproducts out of the film, though.

Donald Qualls
26-Jun-2006, 08:47
Even with an acid rapid fixer, you'd have to measure the negative very carefully with a densitometer to see the loss of shadow detail from fixing for as much as a half hour. Alkaline fixers have almost no bleaching action. And since only gelatin is absorbing the fixer when fixing film, you really don't need to extend your wash -- gelatin saturates quickly, and needs no additional washing for a longer fix once saturated.

28-Jun-2006, 06:02
Thanks everyone. Saves me $100 :)