Name: Vicki
Message: I have some Procion dye powders that have been stored in a dark, dry place for 6-7 years. Will this affect their potency? Do I need to replace them? I'm having several gals from my applique group over for a dyeing session and I don't want it to be a flop. Thanks.

To be sure that your results will be good, it would be best to buy fresh Procion MX dye.

In theory, Procion MX dye powders are supposed to be replaced after one year, because some of the dye will react with moisture in the air and will no longer be capable of bonding to cotton.

In practice, I have used some pretty old Procion MX dye on cotton, but I wouldn't want to use them for anything critical, such as a group dyeing session. It is quite possible that it has all gone bad, in which case it will not stay in the fiber you dye at all! What I have done is use an excess of dye, since a large fraction of the dye powder can be assumed to no longer work. You should be sure to get everything in the dye reaction perfect: leave the dyed items in a warm place overnight, and use the right amount of soda ash. Then, afterwards, it becomes much more important to do an initial washing in cool water, without any detergent except for Synthrapol if you have it (use no detergent at all in the first washing if you don't have Synthrapol), before doing any washing in warm or hot water. A hot first washing, before you get rid of the soda ash and any salt, would encourage the old reacted dye to associate loosely with the fiber in much the same way as the direct dye in all-purpose dye does. Once this has happened, it seems to take forever to wash out the last remnants of excess dye! An initial washing in cold water, before using the hot water needed to really get the rest of the excess dye out, helps quite a bit with this problem.

Old Procion MX dye can still be used as an acid dye with vinegar on protein fibers such as wool, pretty much forever. Procion H dye powders will probably still be good for use on any natural fiber, since they are much less reactive, but you have to steam them to fix the dye.