I’d like to define some dyeing terms.
Pigment – is the actual color molecules. The challenge to dye manufacturers is that the chemistry and size of the molecules can vary dramatically from color to color so it makes it really tough to make consistent dye formulations.
Staining – is when the pigment embeds itself in the fiber without actually bonding. This is what indigo does. Indigo is not an actual dye, it is a pigment and that is why it is so prone to fading. When fibers are stained like this the pigment molecules can eventually shake loose, but may end up stuck pretty tightly and leave a tint for quite some time.
Dyeing – This is when the pigment molecules form an actual chemical bond with the fibers.
Fastness – The strength of the chemical bond between the pigment and fibers in the dye process. It’s often spoken in terms of specific things that it may be vulnerable to, for example: light fastness.
I’d like to add a few things to the dye debate.
First, first just because one thing is food safe and another is not, doesn’t mean one is safe to eat and the other is not. It mean one thing was designed by a food manufacturer and the other was not. By the MSDS sheets, WashFast dyes have fewer carcinogens than food colorings, specifically the blues. According to the UNC biology lab, the only thing that drinking any on the WashFast primary colors would do to a human would turn their mouth funny colors. This is not to say you should go around being careless with them, but they aren’t poisonous.
About the heavy metals. Washfast, Lanaset and Jacquard use a small amount of octavalent chromium in one or two of their colors. This is a completely harmless form of chromium. Hectavalent is the bad chromium. Chromium in and of itself is not bad, it’s found everywhere. It’s a key part of what makes stainless steel stainless.
I would like to say that when you are using food products to dye fibers, you are using them off label. You are using a color that wasn’t planned to hold up long term and under high heat. That it does is a happy accident. If the manufacturer reformulates, or has a bad day it will still pass the food standards, but not the wool standards though.
I have had to contact the manufacturer of my dyes twice in the last 10 years due to a color not striking right. In my experience, certain brands are more reliable than others so if a color isn’t striking right something is wrong. Both times, there had been a problem in the plant and they recalled the whole batch. My customers were saved disappointment and frustration because I could rely on the support and service of using a product on label.
I am also able to give reliable information of the expected color fastness for my dyes, either natural or chemical.
There is a wealth of research and information on natural dyeing, how to do it and what to expect. It isn’t easy, non-toxic, or something you can just jump into on a whim and expect consistent and predictable results. I have high respect for the natural dyers that do such beautiful work. They are true artists.
Those working with food coloring and drink mixes though are working without a net and no playbook.