How do you process Fiber base or Barite double weight enlarging paper ?

[Pere Casals]

Just to clarify about the extended life in a 2 bath system...

Cheers, DJ

I agree... but.

1L of rapid fixer can do 2 m2 of FB paper, but this depends on if the prints have more white or more black. Prints that have a lot of white exhaust a lot fixer. Completely black prints leave the fixer near intact.

So at the end one makes a guess about fixer freshness. With 2 bath system it happens prints always will receive fresh fixer, so you can use fixer with more prints with full confidence. With 1 bath you dump fixer earlier because at one point you are not sure about result.

Ilford says "extremely efficient", and this is what 2 bath is.

Of course single bath is OK, but if prints are "very white" when you have processed 1.7 m2 you can have doubts about optimal result.

[N Dhananjay]

Yes, the rate of fixer exhaustion is directly proportional to the amount of fixing done (i.e., the amount of high values in the print). I advocate using something like Hypo Check to check the state of the fixer every 25 prints or so. Cheers, DJ

[Oren Grad]

I can hardly drain a 16x20 print in 30 seconds; draining it twice from two fixing baths is one minute. I'm at the limit of time for achieving a shorter wash and haven't even included the fixing time!

Good point! I usually print on 5x7 or 8x10, occasionally on 11x14; very very occasionally on 16x20, and that size so far only RC. That certainly affects the relative difficulty of various process sequences in my darkroom.

[Pere Casals]

Yes, the rate of fixer exhaustion is directly proportional to the amount of fixing done (i.e., the amount of high values in the print). I advocate using something like Hypo Check to check the state of the fixer every 25 prints or so. Cheers, DJ

I was cheking film fixer by measuring the time it takes to clear an undeveloped film strip, perhaps also this method could also be used with paper fixer, this is using a 1cm of a 35mm film end...


This test was used to get a fixer time for film, just use 2x the time the undeveloped film need to clear.

With paper, perhaps we can extend paper fixing time acording to the time increase it takes the film to clear with used paper fixer.

Fixer is cheap, but not generating too much waste IMHO it's also important.

Also I'd like to learn by using that Hypo Check, and scientifically mesuring fix/results. IMHO it is something one have to do at least once to learn well when it is important or not.

[Doremus Scudder]

The problem with fixer tests like Hypo-Check or using film clearing time for print fixer is that they are not nearly sensitive enough to register the small amounts of dissolved silver that is the limit for optimal-permanence processing in single-bath fixing. Film fixer can safely contain 10g/l of silver "without serious effect" according to Ilford. That's 20 times their recommended dissolved silver for processing prints for archivally. Assuming that the film-clearing test's "twice the clearing time" shows this level of silver saturation, then it shows you when your fixer is already 20x too exhausted... Hypo-Check is similar; not sensitive enough to show 0.5g/l of dissolved silver (Ilford's recommendation for optimal permanence). The AG-Fix test strips are the only convenient and readily available test medium I've seen for fixing baths that even register down to 0.5g/l of dissolved silver, and that's at the low threshold of the test.

Note that Grant Haist's recommendations for amounts of dissolved silver in a conventional sodium-thiosulfate-based fixing bath for archival processing are even more stringent: 0.05 g/l for the final bath, which translates to only 5 8x10s per gallon for the single-bath method! (see here: https://groups.google.com/forum/?hl=...s/sjs8YfzVX8kJ for Haist's recommendations as quoted by M. Gudzinowicz.)

Bottom line: If you want optimum permanence, use lots of fixer sparingly and use the two-bath method.

Best,

Doremus

[Pere Casals]

The problem with fixer tests...

Thanks for that rigorous information...

So I understand that we can conclude that with 1 bath perfect job is only made when fixer is really fresh, and from then one has to consider what is "without serious effect" for the long term.

2 Baths is not as convenient for large prints, but it's the perfect job...

[Gudmundur Ingolfsson]

Thanks once more for a lot of information and wise discussion on the subject.