# The Science Behind Mordanting
Preparing a fiber for dyeing is not simply washing it. It is a molecular-level chemical engineering process called mordanting. The word comes from the Latin mordere (to bite), and its function is to act as a chemical bridge between the fiber and the pigment. Without this bridge, most natural dyes would simply wash out in the first rinse.
Key Concept
The mordant has available valences that simultaneously bond to the fiber polymers and the dye molecule.
# Fiber Differentiation
Protein Fibers: Wool and Silk
These fibers are composed of amino acid chains with a naturally high affinity for metals. Heat opens the fiber scales allowing alum salts to penetrate deeply. Cream of Tartar is vital to maintain the acid pH that preserves softness.
Cellulosic Fibers: Cotton and Linen
Cellulose does not have readily available bonding sites. That is why we use the two-step protocol: first tannins that bind to the cellulose, then alum binds to those tannins. Without this pre-treatment, the color will be pale and poorly wash-resistant.
# Bath Control: WOF, Temperature and pH
For professional and repeatable results, the concept of WOF (Weight of Fabric) is the rule. Everything is measured as a percentage of the dry fiber weight. Excess mordant can saturate the fiber leaving it harsh or with metallic deposits that alter the final color.
The Thermal Ramp
Heat acts as a catalyst, accelerating the chemical reaction. However, a sudden temperature change in wool can cause scales to permanently lock together, resulting in a felted and shrunken fabric.The pH Factor
Many natural dyes are living pH indicators. pH influences the solubility of salts and the preservation of the fiber. Silk can lose its sheen if the bath is too alkaline. Adjusting pH with citric acid or calcium carbonate is fundamental.# Substances and Safety
Potassium Alum
Universal mordant, colorless and highly effective. The reference for protein fibers.
Cream of Tartar
Assistant that improves fixation and softness in animal fibers. Maintains acid pH.
Safety Protocol
Use pots exclusively for dyeing, never for food preparation.Wear gloves and a mask when handling powdered mordants.
Ensure constant ventilation to avoid vapor buildup.