I received some old procion fabric dyes from a textile artist who longer needed them. Unsure of their age or how they've been stored, I'm using them hesitantly and if it's for something important, I'm testing them first.
Here is a really good example why.
I made this blue dye up as per my usual recipe and added it to soda ash soaked cotton fabric as per
The top photo is the dye solution squeezed through the fabric. I left it to batch for over 24 hours and then took the bottom photo after it was rinsed. You always get some washout and lightening but the amount that I got is nowhere near acceptable and shows me that this particular dye has well and truly lost its potency.
I searched for Multicraft Manufacturing Ltd online and I found that it was dissolved as a company in 2009, so that gives me a hint as to just how old that dye might be!
The reason I was testing this particular dye was because I had been mucking about doing random serendipitous work with the gifted dyes and noticed that none of my pieces had turned out as blue as I expected after the rinse. However, I also had a few pieces of silk organza in the mix and they are quite blue. I've read somewhere that you can use old procion dyes on silk with vinegar (protein fibres work best with acid as a fixative whereas cellulose fibres need a base) and get good results. So before I biff this jar of dye powder I'm going to run one more test on silk with vinegar.
Watch this space.