using fixer multiple times on 8x10, how?

[Daniel_Buck]

My standard way to mix my fixer (TF-4) is to mix up the ammount that I needed for my 4x5 processing, which is 1200ml that would be re-use multiple times (in batches of 6 negatives each time).

Now that I'm throwing rotary processing 8x10 into the mix, it only calls for around 300ml of solution with the way I'm processing them. What would be the best way to re-use my solution for both formats when I'm only using a part of my entire mixture for the 8x10 developing? Would I use the 300ml for 8x10, then mix it back into the remaining 900ml, and mark off a single sheet of 8x10 of usage? And then go back and use the entire (some of it partially used) 1200ml when it comes time to develop a batch of 4x5 sheets?

My guess is that this will be ok, since the more depleted fixer will be mixed back into the less depleted, it'll even out just as if I used the entire batch of fixer on a single 8x10 sheet. Is this correct? Or is this not wise?

[ic-racer]

Don't know what the right answer for you would be, however, I now do all my rotary as one-shot. I few years ago I was printing some negatives from the 80s. Back then, as a poor graduate student, I re-used fixer. Some rolls from the 80s now demonstrate severe degradation of the image. My processing records from the 80s kept track of how many rolls went through each gallon of fixer, and I was under the recommended limit (though, I suspect my storage times were way beyond any recommended limit). The rolls processed with the oldest fixer show the most severe degredation. So, in my case it took 20 years for improper fixing to become evident.

[matthew blais]

Dump the 300 ml into a container and use 100ml of that (or whatever) with some fresh each time.

But, overall I use fresh for each batch. Small price to pay for longevity.

[Ron Marshall]

I process in a Jobo using TF-4, mixed fresh from the concentrate, as you do. I mix 500 ml at a time and put all 500 ml in. When first mixed I do a clearing test (measure the time required, with constant gentle agitation, for a tiny piece of unexposed film to clear). I periodically run a clearing test, when the clearing time has doubled I dump the fixer, and mix another 500 ml.

[Daniel_Buck]

Dump the 300 ml into a container and use 100ml of that (or whatever) with some fresh each time.

But, overall I use fresh for each batch. Small price to pay for longevity.

I'm starting to wonder, if I can get my 4x5 tank to work on my roller, I'll be able to use much less solution for the 4x5 tank (I'm inverting now, so it needs alot of solution). Then I could use fresh 300ml for each batch (each batch would give me 4 uses of fresh 300ml) which would put me close to the limit for 1200ml of initial solution. Formulary suggested no more than about 20 4x5 sheets per liter, but I try to keep it no more than either 16 4x5s (a few batches) or 4 8x10s, or a combo of the two.

[Nick_3536]

Aren't you doing two bath fixing? Safer and actually cheaper.