and store just like glycin
I keep mine in the freezer, in a well sealed jar. Mine came as lightly purple coloured flakes, and so far they have not changed by keeping them frozen.
and yes, it stains. I use mine in a replenished Harveys 777 developer. Combined with the silver in the seasoned solution, it either stains you up front, or after you have been out in a lit environment, and then try to wash up in some soap. The alkanine soap, combined with residual ppd and glycin lets the silver blacken on your skin quite well. Then it si just a matter of waiting for the stained skin to waer away for the stain to fade.
The first round of this tought me that the nitrile gloves I have should be on my hands, and not hanging on the edge of the sink when using this stuff.