Tannin

I recently took on a small weaving commission that required the use of black wool yarn. For a brief moment I contemplated purchasing the wool in the required color and then decided that I could dye it. I was surprised at how easy it was to achieve a rich, deep black color on the wool using only indigo and madder.

Commissioned weaving using wool yarns dye with indigo blue, madder red, black from indigo and madder

It inspired me to continue my current series of color studies, woven in cotton and linen, with an in-depth exploration of black dyes.

Initially, I wanted to achieve all the black hues without the use of an iron mordant. My years of mixing hues with primary colors gave me the confidence to believe that I could mix a good black for cellulose using 3 primary colors: blue, red, and yellow. The key was going to be finding the correct proportions.

The first step was to build up a deep layer of indigo blue (usually 8-10 dips in the vat) followed by a mordant, and finally red and yellow dyes. That red could be madder or cochineal but I chose to use only madder, since that is what I am growing in the garden. My preferred yellow is weld. Each different combination results in a subtle variation. Some “blacks” are more purple, while others are a bit more green, or brown. I began using black walnut and cutch as a substitute for the madder and weld and sometimes added madder or weld to those. Each is a distinct hue, and definitely in the “black” family. I am confident of the lightfastness of these hues because of the primary dyes that have been used.

Dark indigo alone, on far left + combination of cutch and madder resulted in a neutral black

close up of “black” hues in the series on cotton and linen fabrics

These multiple shades of black, put me in mind of the paintings in The Rothko Chapel in Houston, which is the site of a series of large large “black” canvases by the artist, Mark Rothko. These black canvases are painted with layers of crimson, alizarin, and black.

But no exploration of black would be complete without some experiments using tannin and iron. Instead of building up layers of primary colors, I soaked the textile in a gall nut tannin bath, followed by a short immersion in an iron bath. I wanted to use as little iron as possible, but still achieve a very dark shade. I decided that 3% weight of fiber would be the limit of the amount of iron I would use.

Most often, I use ferrous acetate instead of ferrous sulfate because it is less damaging to the fiber. Cellulose fibers are are somewhat tolerant of ferrous sulfate so I did experiments with both. That is where I was most surprised! Without exception, the ferrous acetate resulted in deeper colors than the same amount of ferrous sulfate.

Why? I wasn’t sure. So I consulted my colleague, Joy Boutrup, who always knows these things.

“I think the reason for the grey instead of black with iron sulfate is due to the higher acidity of the sulfate. The acetate is much less acidic. The tannin complex cannot form to the same degree as with acetate.”

The pH of my ferrous sulfate solution was 4. The ferrous acetate was pH 6. (My tap water is from a well and is a slightly acidic pH6.)

The grey and blacks achieved with the tannin and iron are quite one-dimensional compared with those that result from a mix of colors and not nearly as interesting, Yet they are likely a more economical approach to achieving black; the multiple indigo dips, mordanting, and over-dyeing takes considerably more time and materials than an immersion in a tannin and an iron bath.

Always observing always learning, here in the mountains of North Carolina…

The short answer is “no” but here is the longer answer.

I’ve used Aleppo galls (either ground or extract) for years as my preferred tannin. They were recommended to me as being high in tannin and are readily available. Gall is a source of colorless, gallic tannin. I’ve done many tests comparing the Aleppo gall to tannins, such as sumac (from local leaves), myrobalan, tea, and many others but I had never compared different varieties of oak galls.

First of all, what is an oak gall? They are sometimes called “oak apples” and are small, round growths of plant tissue produced by the oak tree in response to the infestation and larvae of a wasp. There are many different species of wasps as well as oak trees. As a result, the galls from each of these is different. The Aleppo gall nut (Quercus infectoria) is hard and dense but can be ground to produce fine particles.

A friend from Missouri gave me a jar of her local gall nuts. She lives in a forest of white oak (Quercus alba) and gathers the galls when they fall to the ground. These galls have a smoother surface than the Aleppo but are just as hard and dense.

Recently I was in New England and was able to gather galls from the scarlet oak variety (Quercus cocinea). These are larger, very light in weight, and seemingly hollow. As a child, we referred to them as “puff balls”.

White oak galls from Missouri

Scarlet oak galls from New England

Scarlet oak galls

I wanted to know something about the tannin quantity of these various galls and if they could be used interchangeably for dyeing applications. They were applied to cotton fabric prior to mordant and dye. I used each of the tannins at 10% weight of fiber, which is the standard amount I use of gall nut extract.

The whole galls were ground with a small spice grinder, and further crushed using a mortar and pestle. Those from the White and Aleppo oaks broke down into fine granules, while the Scarlet oak variety was impossible to grind as fine, as the insides were truly “puffy” and “spongy”. Each of the ground gall varieties and the extract were put into warm water, using separate beakers for each, along with the cotton cloth. They sat at room temperature for 1 hour before the mordant was applied.

white oak gall, ground

scarlet oak gall, ground

Aleppo oak gall, ground

Aleppo extract (from Maiwa)

Left to right: white oak, scarlet oak, ground aleppo, Aleppo extract

I took a portion of the samples with the tannin application and put them into a weak iron bath. When tannin and iron combine a dark grey or black will result. The shade of grey is an indication of the amount of tannin present. The Aleppo gall nuts, in either the ground or extract form, resulted in much deeper shades of grey than either the white or the red oak varieties. The large pieces from the scarlet oak resulted in a very uneven application of tannin. When the iron was applied, the surface was very splotchy and irregular.

Scan 3 — TOP: Tannin only. Although the galls appear to have colorants, an insignificant amount of color attached to the textile. MIDDLE: with weak iron applicaton. BOTTOM: sample shows the uneven application of the scarlet oak gall.

The rest of the samples were then mordanted and subsequently dyed with both weld and madder. The amount of tannin has a direct effect on the amount of mordant that can attach to the textile, and the depth of dye color obtained is a direct reflection of the amount of mordant present. Based on the iron applications, I was surprised at the depth of the color obtained with all of the gall varieties. Although the dye color obtained from the white and scarlet oaks is lighter than the Aleppo, there is still significant color attached.

Scan — Comparison of various galls with madder and weld dye. Left to right: White oak gall, Scarlet oak gall, Aleppo oak gall, Aleppo extract

When using tannin prior to mordanting, it is likely that increasing the amount of gall from the white or scarlet oaks would increase the amount of mordant that attaches and thus the depth of dye color.

Locally harvested galls, when available, are an opportunity to use the local resources and achieve acceptable results.

The Art and The Science of Natural Dyes by Catharine Ellis and Joy Boutrup, available in late fall, is now available for pre-order.

Natural Dye: Experiments and Results

A blog by Catharine Ellis

Black: An Improvisation

Are All Oak Galls Equal?