Quote Originally Posted by zsas View Post
Ian - Let's suppose one mixes 1L of Ilford PQ Universal and 1L of Liquidol. If the person made 10 prints then bottled up the working solution and then 6 weeks later decided to print again, would they have to mix another batch of Ilford PQ Universal? My experience suggests, that Liquidol would be fine, can that be said for the Ilford PQ Universal? The fact sheet for Ilford PQ Universal says mixed working solution bottled lasts 24 hours. If our OP is a small potatoes printer like me, the difference between Liquidol and the others is noteworthy in this regard. Lasting on the shelf is one metric, lasting mixed on the shelf another. If we assume that both PQ and say Liquidol might last undiluted the same amount of time (based on your experience with PQ), then the consumer might want to consider the longevity of mixed developer as a possible advantage of Liquidol....

Why is this bit something the consumer should consider? Print developer is not one shot like say film dev (eg Rodinal).
This is a complex issue because we have no standards, it's bad practice to keep reusing and storing working strength paper developers which is why all companies don't recommend it. Having said that though I know people who use PQ developers in Nova slot processors and replenish and they last weeks dilute.

One issue is print quality with any developers stored partially used and there's to many variables, there would almost certainly be shifts in tones with warm tone papers and then some papers have a degree of developer incorporation so are least affected by developer degeneration.

It's about 50 years since I made my first prints and in all those years I've never needed to store part used mixed print developer. I've used PQ developers for over 40 years without an issue and yes stored for over 2 years.