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If a stain caused by insufficient washing will show up that quickly and clearly I'm wondering whether I'm actually fussing about nothing here... What do you think?

Also, would the toner in this case need to be fresh or could it be stored for a while as a test kit?

Thanks in advance,

Frank

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No, I don't think you are fussing about nothing. After all, the only true test of a prints archival abilities is to have a look at it again in 100 years. If its' turned yellow or fadded you'll need to redo it. Not a responsibility I would like to take on.

You can store your test solution, just as you would store your working solution. BTW, it is believed that a trace amount of hypo remaining in the emulsion after wasing adds to the archival permenance of a print where complete removal of all hypo lends to its' deteration.