Procion MX overdyeing fabric - results part 1 - getting all sciency(ish)

Dyeing with Procion MX is so stable and successful because it is a fiber reactive dye, which means there is a chemical reaction between the fabric and the dye which creates a very strong bond. Unlike paint, that sits on the surface of the fabric, the dye forms a covalent bond with the fabric. If you want a good scientific explanation relating to Procion MX, go here. 

Overdyed fabric

If you want a quick word picture here it is (I can imagine my daughter, the chemist, rolling her eyes..): picture the fabric with lots and lots of cute little hands, fingers waving in the air. Make sure your mental picture is cute, or it starts to look like a horror movie - zombie fabric is coming to get you, run! Now imagine your dye stock also has lots and lots of cute little hands, fingers waving in the liquid.

When the dye stock meets the fabric, the hands reach out to one another and the fingers intertwine, making bonds between the fabric and the dye. The number of hands (technically dye sites) on the fabric depends on the type of fabric you have chosen. The number of hands in the dye stock depends on the strength you have mixed, i.e. the ratio of dye powder to water. While you can bump up the ratio of dye to water, after a certain point you are just wasting dye because the number of dye sites on the fabric is the limiting factor. After all the dye sites are filled, there is no way additional dye can react with the fiber and it will just wash out and down the drain.
 

Overdyed fabric

This is important for overdyeing. If all the hands on the fabric are already holding corresponding dye stock hands, the overdye color will have no impact. However, if you have used a diluted dye stock for your first dye, there will still be fabric hands without dye partners and they will reach out and grab the dye hands of the second dye stock.

Diluted base colors overdyed

 Now I have to step away from my analogy for a moment to point out that dye is transparent. Unlike paint, which covers your first color, dye will not completely mask your first color. Moreover, the base color will influence the second color.

Neutral overdye

It sometimes gets confusing when people talk about overdyeing. Some people use overdyeing to mean dyeing a value gradient from light to dark, or dyeing a mixture of two colors from pure color A through increasing amounts of color B till the last color is just pure color B. However, what I am doing here is dyeing and washing out a base color, then dyeing a second color over the first base color.

Next post: analyzing the results of my experiments.