A couple of questions about chemistry shelf life
I've just had my third session in my new bathroom darkroom and now I've got everything working I'm thinking about how much I can reuse certain chemistry.
I am using Ilford PQ universal as developer and Ilford rapid fixer. I use 2 litres of both and store it in 5 litre chemical containers. I've reused the developer a couple of times with no problem but have only ever used the fixer as on shot 1+9 (only stored todays mix)
I read somewhere about how many sheets of 8x10s you can get out of PQ Universal and it is a lot more than I'm producing, but is the fact that it's in contact with so much air in the container going to oxidise it and exhaust it quickly? After a couple of uses should I discard half and top up with new chemistry or just keep track of how many sheets I process?
And for the fixer should I continue to one shot it, or can I reuse it? I'm going through it quite quickly
Anyway at least today was the first day I got a couple of prints I'm not ashamed of
With regard to the fixer, if you look on pages 2 and 3 of the data sheet for it (http://www.ilfordphoto.com/Webfiles/...7111531653.pdf ) you will see capacity figures for use with and without replenishment.
For a bathroom darkroom, it rarely makes sense to use replenishment, but if you have any long, multiple print sessions it may make more sense.
If you are printing on fibre based paper, two bath fixing is strongly recommended.
I would be cautious about using 5 litre containers for 2 litres of chemicals. Your containers should have as little air in them as practical.
And in case I have misunderstood, please confirm that you are waiting until just before you use the developer and fixer before you mix up just enough for your use. You should only use as much of the concentrate as you need and leave the rest in the bottle.
EDIT: I don't use Ilford PQ Universal, but expect that much of what I say about fixer applies to it as well. I would certainly recommend reviewing Ilford's data sheet for it.
“Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”
Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2
When you use chemicals only occasionally, you might not get the full capacity if you re-use it. I don't use developers except as one-shot. When I mix up a batch of developer, in US measure, I mix a gallon and divide it into four quart bottles. So each bottle keeps "forever" until I open it. Then I figure it's got a few weeks before I have to use it or lose it.
Thanks for the answers everyone. Yes I'm mixing just before I use but there has been one week that I have stored developer for 7 days and used it again without problems, never reused fixer but stored it today just in case.
Originally Posted by MattKing
I think inlight of this thread I might try to find some smaller containers so I can fill to the brim with developer and see how that works.
Developer mixed to working strength will not keep long. Your enemy is oxidation, and you are making matters even worse by storing your developer in a partially-filled bottle. My recommendation: Mix you developer to working strength from the concentrate just before your printing session. Mix just enough for your printing session. Discard it after the session, or, if your session was fairly small, store the developer in a full bottle and see if it works the next day. I often get an extra day out of my PQ developer (not Ilford). That said, the working solution will rarely last more than a couple of days. Toss it and mix new if the activity seems low. Developer is relatively cheap; a lot cheaper than a few sheets of paper these days, so when in doubt, mix new.
Originally Posted by Saturnine_Zero
Your fixer will last a lot longer. Do READ THE DIRECTIONS and the data sheet linked to above. All the information you need is there. Take the time to figure it out once and write everything down. Then you'll be good to go.
If you print on RC paper, you can use the single-bath method and Ilford's capacity recommendations. Two-bath fixing, however, will get more out of your fixer (you'll have to store your fix in two bottles though). Ilford gives not only capacities based on throughput, but fixer lifespan for various containers (e.g., full bottle, partly full bottle, open tray, etc.). These are in the directions... You can store fixer for quite a while in a full, tightly-stoppered bottle and reuse it as needed till print capacity has been reached. Other storage methods have shorter fixer lifespans, but may be enough depending on how much you print. When I'm printing, I just leave two fixing baths in open trays. I always reach capacity before the 7-day lifespan is reached.
If you print on fiber-base paper, do use the two-bath method described in the data sheet. I use throughput as a capacity guide at a bit less than the Ilford recommendation (just to be on the safe side). As you grow as a printer, you may become more interested in print permanence. Two-bath fixing and testing with a residual silver test to make sure your particular work-flow is doing its job is the final step in achieving and gaining confidence in your processing. There's lots of info here on the forum; search and read, read, read.
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Thanks for your answer. I guess I was trying too hard to avoid waste. At 1+9, 5 litres of concentrate will last me 6 months if I mix just what I need before printing and one shot it. Not such a great dollar cost. Although I haven't looked into how oxidation effects the concentrate itself.
Originally Posted by Doremus Scudder
I don't want to give the impression I haven't read the data sheets, I always read everything. It just takes a few reads to actually remember anything and have only ever seen people refer to using fixer as one shot when developing film. So I'll take notes before next time!