Mordants make fabric colour fast by impregnating it with a compound – usually a salt – that will also readily attach itself to the dye as well. Many compounds will function as mordants. We use two traditional, naturally occurring salts, aluminum sulfate and sodium sulfate.
When dyeing with natural dyes the intent is to use a mordant that avoids toxicity. Aluminum Sulfate is used as a flocculant in water purification. Sodium Sulfate is often found as a precipitant on the shore of alkali lakes.
Most people do not realize that hair colouring uses strong and toxic salts in order to make synthetic, laboratory-derived dyes adhere. All-natural is always best…
Aluminum Sulfate –
Aluminum sulfate, Al2(SO4)3, is a salt, a type of alum, that is commonly used for water purification (flocculating), mordanting, and soil remediation (pH). It is readily available through agricultural supply stores, although before purchasing it from sources that use it for anything other than fabric its content should be thoroughly reviewed as some impure forms contain iron (Fe) which will gravely and negatively affect the dyeing outcome. Its MSDS lists its primary risk – exposure to large amounts – as an irritant upon ingestion or inhalation.
Sodium Sulfate –
Sodium sulfate, Na2SO4, is another naturally occurring salt. Originally known as Glauber’s salt, it was used as a laxative in the 1700’s. Today it is commonly used as a bulking agent in detergents, a part of the pulping process in paper production, and as a mordant in the fabric industry. A very pure form of it is mined in Saskatchewan where it occurs on the surface at Chaplin Lake which is a Western Hemisphere Shorebird Reserve Network. Its MSDS lists its primary risk – exposure to large amounts -as an irritant upon ingestion or inhalation.