ILFORD HYPAM fixer is similar enough to the Multigrade fixer that capacities are the same. Mulitgrade fixer cannot be used with a hardener.(posted 8419 days ago)For film, ILFORD recommends a capacity of 19 rolls of 135-36x films per liter of working solution. It is possible to get slightly more with extended times, but this should not be carried too far, as it is impossible to tell from looking if the fixer has removed all of the argentothiosulphate compounds. A second fixer bath, as has been mentioned, will assure complete fixing even if the first bath is pushed beyond normal capacity.
For paper, we recommend a capacity of no more than 40 RC or 10 Fiber based prints per liter. This does increase to 40 Fiber based prints if following the ILFORD Archival Processing Sequence, as the second fix and the wash aid bath ensure that all residual compounds are removed.
The film chip test is by far the best way of testing the fixer. This will work with either film or paper fixer. Tests such as Edwal's Hypo Check will show if the fixer has become saturated with silver, but will not tell you if the fixer has become less effective due to other reasons.
Although it is stated on the bottles that the storage time is 7 days for the working solution, I have found that it usually keeps much longer, as long as it is kept in a closed bottle. Generally, if the capacity has not been reached, and there is no sediment in the bottle, it will probably still be usuable for several weeks with no problem. Of course, it is a good idea to check with the film chip anyway.
We do recommend keeping seperate fixers for film and paper, due to the buildup in different waste products from the two materials. In a pinch, you can use the same fixer, but overall capacity will diminish.
Although ILFORD generally recommends using fixers at 1+4 dilution for paper processing, this is done to improve speed of fixing, and therefore subsequent wash times. Capacity of the fixer is determined by the amount of silver present in solution, so a liter of 1+9 fixer has about the same capacity as a liter of 1+4, although fixing times will have to be extended.
David Carper ILFORD Technical Service