Are All Oak Galls Equal?

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”. 

 

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.  

IMG_2702
1 gram of each gall source

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. 

 

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.