The bark from the oak tree produces tannin which was traditionally used for tanning leather. It is a substantive dye (does not need a mordant to bind to the fibres in a fabric). When used on its own, it achieves shades of beige-grey-tan. After soaking in a dilute solution of ferrous sulphate (Iron mordant), known as saddening, it will produce dark shades of brown to black. An orange can be achieved when Titanium Oxalate is used as the after-soak.
Tannins are used in dyeing with natural occurring materials in a number of ways. As a substantive dye, they do not need the use of a mordant when used on proteins (wool, hair, feathers etc) They are also used as a key component in botanical printing as well as preparing cellulose fibres for dyeing with natural materials.
Cellulose fibres and fabric such as cotton and linen are prepared for dyeing by cycling Tannin with Alum. The Alum makes natural dye colours chemically bond and therefore washfast. However, it does not react with cellulose fibres in the same way as it does with protein fibres such as wool and silk. Tannin is used alongside the alum to pre-mordant the cellulose.
You should be aware that most tannins will leave a residue of colour and tint the colour from the natural dye, and this may be a desired effect. To avoid this and to retain the fibre’s natural colour, Aluminium Lactate can be used as an alternative mordant for cellulose.
This is a non-hazardous product. May cause irritation to eyes, skin, by inhalation or if ingested. Normal safety measures should be observed.
