Udated December 8,, 2020.
Suppose you are like most stitchers; you probably don’t think much about how your threads get dyed. And we shouldn’t really; it’s kind of like knowing how a car engine works — nice but not essential for the task at hand.
But you will find some terms used over and over. Today I’m going to clear up some of the confusion by defining and explaining some terms.
To dye, you will need thread, water, dye, mordant, and fixative. Changes in each of these will affect the result.
Threads (or fabric) to dye comes in two forms: Neutral goods (also called ready-to-dye or RTD) and already dyed goods. Already dyed goods are the kind of threads we normally use. RTD goods are the natural color of the fiber source. For example, the natural color of wool is off-white. RTD wool will always be this color. If you ever see a pure white wool, you’ll know it has been dyed or processed to become that color.
Water is usually just the water from the tap. Because the mineral content of water differs from place to place, this may affect the dye’s chemicals. If a thread company moves from one location to another, the water will change. Because this affects the dyes, it may take a while to recreate some of the colors.
Mordants are put into water, and the thread is soaked in them before dyeing. While the primary purpose of a mordant is to help the dye penetrate the thread, different mordants can also affect the final color, sometimes significantly. You can see in the picture above how different mordants affect the end result.
While there are many types of dye, they break down into two classes: natural and chemical. Natural dyes come from plants, minerals, and animals. These have almost entirely been replaced by chemical dyes, which were invented in the Mid-nineteenth Century. All dyes work by causing the color to penetrate the fibers of the thread or fabric. There are different dyes for different kinds of fibers because different fibers take up dye to different degrees. A dye is different from paint or ink because of this penetration.
After the thread is dyed, the dye needs to be made permanent. This is done by using a fixative. Depending on your dye, the fixative can be as simple as ironing it (heat is a common fixative). Another common fixative is vinegar.
Once the thread is dyed and the dye is fixed, it is rinsed to remove excess dye. The dyed material is rinsed until the water is clear, usually under running water. It can take repeated rinsings to remove all the dye.
Sometimes you can do the rinsing yourself; if the thread is marked “colorfast,” Colorfast means wetting the thread will not completely alter the color but only rid the thread of excess dye. If the thread is not marked colorfast, the dye may run and enough dye may be removed to alter the color (this has happened to me).
That is the basic process that creates all colored thread. If the process is done in small batches, using mostly non-mechanical means, we call the thread hand-dyed. Often, but not always, hand-dyed threads show some variation in shade or, less often, color.
Overdyed threads take already dyed thread and dye another color over it. If you use a blue dye on RTD thread, the result is blue. If you overdye blue on a gray thread, the result is a muted blue. If you dyed the same blue on a yellow thread, the result would be green.
Space-dying is the technical term for painting threads with dye. The thread is stretched out and would around pegs or poles. It can be wet or dry (each gives a different effect). Dyes are painted onto the thread in a specific order. However, the space between colors, the length of color, and just about anything else can differ throughout one dyelot (one batch of one thread dyed at one time).
Many of the threads we call “overdyes” are hand-dyed or space-dyed.
Ombre is yet another dyeing technique used but that you won’t see on tags. Ombre threads are put into the dyebath (dye + water) then gradually pulled out of the bath so that there is a gradation of color throughout. Do remember that while a thread could be dyed in this fashion, it might be skeined to look as if it was not. This is because the skein’s circumference is different from the circumference of the threads as they were dyed.
Although you may not see much of this information on your thread tag, knowing the terms for dyeing will make you better able to identify and use different threads.