Shelf Life of Natural Indigo and “Pasting-Up” Your Powder

Q: I purchased some indigo dye several years ago and the label on the jar says it is 100% natural indigo and to use within 12 months. The contents are in large chunks. Must I throw it out or is it still useable?

A: Natural indigo is a stable pigment and has no set shelf life. As long as it is kept cool, dry, and out of light, I believe it can be used in perpetuity... I've used pigment that is many years old with no ill effects.

The chunks themselves will actually present you with a larger problem! Indigo needs to be "pasted-up" before use. Pasting up involves hydrating the indigo and getting it evenly dispersed in a pasty suspension. If you don't properly do this, you'll end up with chunks of pigment in your vat that will either be wasted or smear onto your fabric. A nice way to begin the “pasting up” when your indigo is in dried chunks like yours, is to run your chunks through a coffee grinder (though this creates a lot of dust). From there, I put the pigment into a plastic bottle with a bunch of pebbles and add just enough water to turn it into a thick/syrupy paste and SHAKE. I don't have a set amount of time to tell you here, but just know that you can't overdo it. This will make sure that the indigo is all broken up and available to be dissolved in your vat. Pour the resulting paste into the vat and rinse the bottle and pour the rinse in as well as many times as it takes until the stones and bottle rinse clear. From there you can use any vat recipe you prefer!