BPO: Mordants

Service Description

What is a mordant? Mordants and tannins are two different things, but sometimes used for the same purpose: improving light-, wash- and rub fastness of fabrics, paper or hides. Tannins are always plant derived, so we call the process tanning. Mordants are mineral salt that come from the crust of the earth. Nowadays most are man-made. They behave like a kind of glue or connector between fibers and pigments and tannins that are present in the leaves. We could consider it a fixative. ​We call the use of mordants before dyeing or printing: mordanting. Using mordants after a dye or print process to change colors is called post-mordanting. The only exception for the terminology is so-called chrome tanned hides, where a solution of chemicals, acids and salt is used to 'tan' a leather hide, to make it softer. ​In natural dyeing and botanical printing we use mordants for; Improving light-fastness of the pigments on the surface we are printing on. Unmordanted fabrics will fade in direct sunlight, this is less relevant if you are using tannin-rich leaves. Improving wash- and rub-fastness of the pigment on the surface we are printing on. The pigments could easily wash out or rub off, unless we use a mordant to connect the colour to the surface. We can use mordants to change the color shade of plant pigments. Different mordants will create different shades, as we will see below. ​Handling mordants Mordants should always be handled with care. Wear a mask while handling fine powders and wear gloves. Do not work outside when there are winds. Work in well ventilated areas. When working inside, open a window and use a vent. My method for mordants is to always measure the mordants according to the weight of the fabrics in relatively low percentages, as to avoid pollution through waste waters. Store mordants in closed containers, clearly marked, out of reach for children and pets Discarding mordants Most leftover mordant baths can be discarded by flushing them in the sewer system with plenty of water, or in a soakaway under trees and bushes in your garden.Most plants love a little alum or ferrous sulfate. I can assure you the percentages left of mordants in the water after you finish your mordanting process are benign. Check your local ordinances when in doubt. Do not dispose of leftover mordant baths in a septic tank. ​Re-using mordant baths You *can* re-use mordant baths, but you will not know how much of mordant salt is left there to be effective.