Textile Notes: Dyes

All colors will agree in the dark.

– Francis Bacon

Photo source: own photo

Have you ever thought about the chemistry behind textile dyeing? Well, it is pretty easy to understand! You have a chemical solution, and there is color substances in this solution. Those substances move from the solution to the fibers of your fabric. Voila!

Of course there is more complicated processes and other things to consider. However the basic idea relies on this transfer.

Actually there are different types of coloration in textiles: Dissolve dyeing, Pigment coloration, Printing and some other new technologies. However this post only covers the dyeing.

Colorant = The substance that colors something (here, something is your textile material).

There is 2 different classifications when it comes to colorants: one is based on the method of application, which depends on your fabric; and the other is based on the chemical structure.  We will look at the first classification in this post:

Direct Dyes: This type is mainly for Cellulosic materials (such as COTTON). There are some cases that people use direct dyes for proteins because of the similarities between the chemical structure of this dye and the chemical structure of the dye used for protein fibers. It is easy to use and cheap. 

You will add dye directly to the bath.

But do not forget to add salt. OK, why we are adding salt? First of all, it is NOT to fix the dye! However, it helps dye molecules to move onto fiber and to bond better. In other words, it increases the dye absorption.

The pH of the dye batch should be Neutral(around 7) and temperature should be 95-100°C.

The result will not be so bright. So we usually do NOT use it for light colors but for heavy shades.

Reactive Dyes: This type is for both Cellulosic and Protein fibers. Dye molecules chemically react with fiber; so this means they provide good to excellent wash fastness. Think about it: the dye molecules and fibers are bonded chemically, this means the connection is strong and will not be broken easily by washing.

They provide BRIGHT colors. Why? Because reactive dye molecules are small. Thus; more molecules can bond with the fibers and result light shade.

Again, if you want heavy shades, you need to add salt.

Vat Dyes: The day class with ALL THE BEST properties. It provides better saturation, better color and wash fastness and it easily handles Chlorine bleach. However, it is really expensive and the dyeing process requires chemicals and some chemical processes.

Dyeing temperatures and pH conditions vary. Dyeing processes depend on the material.

This dye class is excellent for the light-medium shades.

Sulfur Dyes: This dye class resembles Vat dyes but it is cheaper. It has pretty good light, wash and color fastness. It is often sued for Black Jeans. This is mainly because of the wash fastness. Even you wash a black jean dyed with Sulfur dye, it will still be black and she shade will not be changed (the light black will be light black, the dark shade will remain as well).

However there are some problems after dyeing such as dull, metallic appearances, probably caused by oxidation. This brings us an issue: shelf time. The retailer will want to sell those materials quickly.

Also, sulfur dye has very low bleach fastness, so you need to be extra cautious when you as your material.

Disperse Dyes: This type of dye is mainly for acetate and polyester based materials. The disperse dye molecules are not in the dyeing solution like direct dyes, the dye is a dispersion instead. They need a chemical, called “dispersant agent” to form a stable dye bath.

Since it is widely used for polyester fibers, high temperature is required(around 100°C).

Acid Dyes: This type of dye is for Protein fibers and Nylons. We have to use an “acid” during the dyeing process (this is why the dye gets its name). Acid helps fibers to generate “dye sites“, where the dye molecules will have a chance to bond.

However, using acid is the number 1 problem, since the amount of acid might be crucial for the environment or for people who conduct the dyeing procedure.

Again we will get higher depth of shade if we add salt.

Basic Dyes: In contrast to acid dyes, basic dyes do not get their name because of the alkalis used during dyeing process. Actually, we do not use alkali for this dyeing procedure. However, it is about the “charges” that dye molecules carry. As we know, molecules carry positive (+) and negative (-) charges; and basic dyes are the only dyes carry (+) charges.

This dye class gives the MOST BRIGHT colors and they are the MOST SATURATED dyes. However, they have very poor colorfastness. Because their positively charged structure is not as stable as the other dye structures.

It will not need chemicals other than salt and it is cheap.

Dyeing Cheat Sheet

Cellulosic Fibers : Direct, Reactive, Vat, Sulfur

Protein Fibers:       Acid, Reactive

Polyester Fibers:   Disperse

Acetate:                    Disperse

Nylon:                       Acid

Acrylic:                     Basic

Did You Know: If you use Glue (to bind), you can dye any of these materials with Pigment Dye.


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