Protecting Your Indigo-Dyed Pieces From Fading: Proper Scouring and Soy Milk Treatment

Q: Are there ways to protect my indigo-dyed fabrics from fading? It seems like some of my indigo-dyed fabrics have faded from being dried in the sun - is that possible?

I've heard that soy can be used to help fix the indigo pigment. Can you let me know how to do this?

A: Fading can happen on indigo dyed pieces for a number of reasons: incomplete or insufficient scouring of fabric prior to dyeing, under-reduced vat conditions resulting in weakly adhered dye to fiber, ultraviolet light as well as ozone exposure. As a general matter, if you are drying your pieces outside keep them in the shade whenever possible. Indigo is very susceptible to fading when it is exposed to UV light while wet.

For long lasting blues, first, make sure your fabric is totally scoured prior to dyeing : boil it in soda ash for at least 4 hours, then rinse thoroughly. Cotton (and other natural cellulose fibers) are often sheathed in waxes and pectins which are not ideal bonding sites for indigo because they can (and eventually will) separate from the cellulose fibers themselves, taking any indigo attached to them. Properly scoured fabric is free of these compounds and you’ll find that those fabrics dye more easily, evenly and the colors hold up best.

And yes, soy milk treatments can add a layer of protection against crocking (fading from rubbing) and UV exposure by (to my knowledge) adding a protein “glazing” to the piece.

When I do soy milk treatments, I make the soy milk from scratch. I soak the beans for 24 hours, blend in the excess water, strain off the solids, and use the liquid. I suggest making your own soy milk as well. Purchased soy milk has gone through a number of processes to make it shelf stable and it contains other ingredients. I don’t have enough experience to say for sure that purchased soy milk would not work as well as homemade soy milk, but I do know that it smells and feels different than fresh soy milk.

To treat your piece, dip it into the milk to wet it and then wring the piece out and allow it to dry flat. You will want to rotate the piece periodically as it dries otherwise the fabric has a tendency to stick to whatever surface it is on.