The world of tannins is still surrounded by certain level of mystery. Their chemistry behaviours are yet to be fully understood.
The importance of this type of compounds derives from its usage both as an excellent mordant for cellulose fibres, and a source of colour. These have been known to human as early as the early humans and most traditions around the world have use there local tannin rich resources. They are easily available making their use sustainable in today´s world.
There are many types of tannins and can be divided in three main families:
Gallic tannins
They are clear tannins that do not add much colour to the fabric. The Oak galls and bark, and Sumac leaves and galls are excellent sources of gallic tannin.
Ellagic tannins
These contain a lot of flavonoids that will add a yellow colour to the fabric. Some traditional ones like Myrobalan, Pomegranate peel, and Henna.
Catechic tannins
This family will add brown or reddish hues to the fabric. These tannins are quite common like Black tea, Cutch, Quebracho and Chestnut bark.
Cork Tree Acorn Cups left to soak
Contrary to what feels logical, the tannins on tree bark are mostly found on the inner side, not the outside. Thus, chop the bark into small pieces, or shave it to expose as much inner bark as possible to extract the tannins. Leave to soak for even a week before heating for one of two hours, and let cool and rest for a few days afterwards.
Colours
As we read before, tannins colour can vary from almost no colour at all, to yellows, reds, and browns. However, they all share a common characteristic, any contact with Iron and the colour will almost immediately shift from lighter to darker greys and blacks. With ranges of brown, green or reddish under tones. These are durable, wash and lightfast.
Protective and Antibacterial Properties
Tannins add other benefits to textiles beyond colour. Tannins are large molecules that can improve cellulose fibres cross-linking. That is, they help fill micropores within the fibres thus improving the resistance to abrasion.
Tannins are also powerful antioxidants, and so they protect fibres against environmental factors such exposition to ultraviolet light.
The Persimmon tree, also known as Kaki with its delicious winter fruits, is packed with a specific type of tannin. In Korea and Japan it has been used for centuries for its many properties. It makes clothing almost waterproof, antibacterial, and the colour does in fact intensify and darkens with exposure to sunshine, unlike almost any other dye that I know of.
