Understanding natural tannins and the best ones for dyeing

In the realm of natural dyes, there exists a fascinating and ancient class of compounds that hold the power to infuse colours into textiles and materials – they’re called tannins. 

Derived from the bountiful embrace of Nature itself, tannins are a group of polyphenolic compounds found abundantly in various plants and botanical sources. These remarkable substances have been utilised by several cultures across the globe for centuries, and their transformative potential harnessed to create a vibrant spectrum of hues that defy the passage of time. 

And just as nature weaves intricate patterns through seasons, tannins interlace with fibres to gift us with colours of beauty and significance. 

So let’s get into exploring the best tannins for dyeing!

What is a natural tannin?

During the Paleolithic period (around 40,000 years ago), people started making moccasin-like wraparound footwear out of softened animal skins, or rawhide. This seemingly simple advancement gave humankind a major leg up in long-distance travel and marked the beginning of leather-making. 

When formerly nomadic tribes established agricultural settlements, animal husbandry provided a steady and easily accessible source of food and rawhide. This allowed our ancient ancestors to develop a process that made hides more durable and less susceptible to decomposition. This process evolved into the craft known as tanning

Tannins are very astringent phenolic biomolecules that can be found in many plants as a defence mechanism against predators. It’s also believed that they help regulate growth.

They also often occur as excretions in the bark and other parts of a plant (especially leaves, fruits, and galls)!

Fun fact: Did you know that tannins and their astringent effect are responsible for making our mouth dry and pucker when we eat unripe fruit or drink red wine or tea? How cool!

What does tannin do to fabric?

Well, simply put, tannins can be used to both prepare fabric and dye fabric. 

They can also be divided into 3 categories: 

  1. Gallic tannins: They are clear and don’t add much colour to the fabric (oak galls, oak bark, tara and sumac)
  2. Ellagic tannins: They tend to add a yellow colour to the fabric (pomegranate peels, henna and myrobalan) 
  3. Catechic tannins: They tend to add brown and/or reddish colour to the fabric (black tea, cutch, quebracho and chestnut)

Tannins are excellent dyestuffs, but they are also important for preparing cellulose fibres in a way that helps soak up colours better. They assist during the mordanting stage of cellulose fibres. Alum, for example, doesn’t bond very well with cellulose fibres. However, tannin bonds well with cellulose, and once treated with tannin, alum will combine with the tannin-fibre complex.

In fact, one of the mordanting techniques for cellulose fibres involves treating the fibres with a tannin solution first and then mordanting.

How do you make tannin mordant? 

According to Mother Earth News, when it comes to discovering tannins for dyeing, two of the most popular sources for making a tannin mordant are oak galls and sumac leaves. You can use either oak galls or sumac leaves of the same fibre weight. 

You’ll need:

113 g of plant fibre

1 teaspoon of powdered oak galls (available to buy in most dye suppliers)

What you need to do:

  • Soak your fibre overnight in cool water.
  • Place the oak gall powder in a stainless steel pot with 16 to 23 L of water, and stir to dissolve. Bring the solution to a simmer at 182 degrees Celsius, and let it simmer for 30 to 60 minutes.
  • Remove the pot from the heat. Allow the tannin bath to cool down from hot to warm.
  • Lift the wet fibre out of where it has been soaking, and submerge it in the tannin bath. Let it steep for 8 to 24 hours.
  • Remove the fibre from the tannin bath. Rinse the fibre in lukewarm to cool water and hang to dry.

What comes first, mordant or tannin?

In natural dyeing, the sequence of using a mordant and tannin can vary based on the dyeing method and the outcome you desire. However, as a general guideline, the sequence typically involves using tannin first and then mordant.

Here’s the usual sequence:

  1. Tannin Treatment: The process usually begins with treating the fabric or fibre with tannin. This step helps create a surface that is receptive to the dye molecules, improving colourfastness and enhancing colour uptake. The tannins form a bond with the fibres, creating a foundation for the dye to adhere to. After the tannin treatment, the fabric is usually lightly rinsed and dried.
  2. Mordanting: Once the fabric has been tannin-treated, it’s common to proceed with mordanting. Mordants are substances that further enhance the fixation of the dye onto the fibres. They can alter the colour, increase lightfastness, and improve the ‘washfastness’ of the dyed material. Common mordants include alum, iron, and copper. The fabric is immersed in a mordant solution and then rinsed before dyeing.
  3. Dyeing: After both the tannin treatment and mordanting, the fabric is then ready for dyeing. The dyeing process involves immersing the fabric in a solution containing natural dyes. The tannin-treated and mordanted fibres are better prepared to absorb and retain the dye molecules, resulting in richer and more stable colours.

Also, as a quick heads up: always keep in mind that there can be variations in this process based on the type of fabric, the specific dye materials being used, and the intended results. Some dye recipes might call for a slightly different sequence, such as simultaneous tannin and mordant baths or using a combined tannin-mordant solution. Additionally, certain dyes and fibres might have specific requirements that influence the order of treatment.

The best natural tannins for dyeing 

If you are looking for dyestuff with high concentrations of tannins to omit the mordanting part of the natural dyeing process, have a look at using the following:

  • Tree barks in general (willow, quebracho, sumac, maple, wattle, eucalyptus, red mangrove, aspen, witch hazel, chestnut)
  • Oak (bark, leaves, galls)
  • Avocado pits
  • Coffee, black tea

Explore the art of natural dyeing with me

There is nothing greater than experiencing the art of natural dyeing and understanding how to use natural tannins. My online workshops and courses go over everything crafters, designers, and artists need to know about applying colour to natural fibres in a safe, long-lasting way.