Shelf life of Selenium Toner working solution

Jose A Martinez said:

How?

Click to expand...

I find that if I wait until my toner is taking about 50% longer than when it was fresh and I add 7.5% of concentrate by volume, I get back very close to my original toning times. (I originally mixed at 1:9...I get close enough to that using this method.) I add a bit of water to bring the whole thing back to 2L (but it never takes much water to do that).

I've never tested the solution to find out what the actual concentration of selenium is (and I have no idea how I'd go about doing that), but this method has worked for me for quite a whlie.

It is important to filter the solution occasionally...again, I don't know why, but I do know that it is. I use unbleached coffee filters and a funnel that I reserve for use with selenium toner only.

When you start to see a lot of little black bits (silver selenide), your Se solution is starting to go. When you accumulate a lot of this precipitate, you should notice that it is taking longer for you prints to tone. This is the time to throw it out. In many soils, particulary in the arid SW US, Se is encountered relatively in high levels. When these levels get too high, it will effect plants. I think dispersing it in the soil is the best way. Typically, I find that a 1/2-gallon of working 1:20 solution will do about 40 or more 8x10 prints before it gets to this stage.

Thanks, Mongo and Hortense.