Capacity of TF5 Fixer Question

[An Le-qun]

I have processed ten 5x7 sheets of film in 3:1 TF5 fixer--three parts distilled water (375ml), one part TF5 liquid (125ml). I have tested the clearing time before each sheet after the second one, and it's still less than 30 seconds after 9 sheets. In fact it seems to clear as rapidly as it did after the second.

I doubt that TF5 has unlimited fixing capacity, but I'm wondering how far I should trust the "twice the clearing time" conventional wisdom (I have been leaving the film in the fixer for thrice the clearing time for the last three sheets, just out of fear!).

Do any of you have advice on how far to trust this particular brand? Again, out of fear, I would probably dump the stuff if the clearing time got to be 40 seconds...but that would be flying blind, also.

 

[ROL]

Just follow the directions for capacity on the label. I stopped using TF5 in favor of old TF4 because of the formation of precipitate and odd odor in the working solution, after only a short duration. TF4, which I believe has the same capacity of TF5, allows for 1400 to 1600 sq. inches per working solution. I calculated this as 70 sheets of 5X7 per half gallon of working solution. I rarely use half that number before mixing fresh, just to be safe.

 

[Photo Engineer]

TF4 and TF5 should have roughly the same capacity. TF4 is alkaline and has the odor of ammonia. TF5 is neutral and should have very little odor unless one does not use a running water rinse after the developer or a stop bath. In this case, the fix can take on the odor of an acid or a base.

PE