I would like to know whether you should keep used, made-up toner between toning sessions. It makes sense economically and environmentally, but I have no idea whether it would actually do more harm than good form the print's point of view :confused:
Mark,
I keep it for a long time after mixing it to a 1+15 dilution and don't see any change. I don't tone all my pictures so the amount of use is somewhat limited but for keeping it will last a long time. >6 month
I use the Kodak product, and keep the made up solution until it ceases to work. The period seems to depend on use rather than length of time, generally it is many months.