First of all, I know that my well water is acidic. It measures about pH 6.0 here in the mountains of North Carolina. The water is ideal for most dyeing. There is no iron or other minerals that might dull the colors. The acidity is another issue.
Most of the yellow dyes in my garden, or those that I might gather locally, are flavonoids. That means that they require a mordant in order to attach to the textile. No mordant means no yellow. It’s that simple. Some of the dyes may also contain some tannin or other colorants but the yellow is what we’re talking about here.
Last summer Joy Boutrup and I taught a class together at Penland School of Crafts, located near my home in western North Carolina. A student in the class was especially interested in gathering local plants for use as a dye source. She struggled to get the locally gathered dyes to attach to her textiles, especially onto mordanted cotton.
Joy had the answer-of course!
When the dye meets the mordant in a textile, an insoluble lake is formed. This lake is formed most readily in neutral or slightly alkaline conditions.
An alum mordant makes a very strong bond with wool but there is no chemical bond between cellulose and the mordant. Instead, the mordant is deposited as an insoluble compound on the textile.
An additional issue is that many of our local plants are acidic. When the plants are boiled in our already acidic water, the pH of the dyebath becomes so low that the dye may struggle to attach to the mordant in the fiber. In fact, the mordant in the cotton can be damaged or even removed if the bath is acidic enough. This is exactly the reason why we don’t add an acid to a cochineal bath when dyeing cellulose. The mordant would be damaged and little dye attaches.
The remedy: Add a small amount of chalk (calcium carbonate) to the dye bath to neutralize the acid that is present. This will do no damage to the dye or the textile. Chalk is not an alkaline but will neutralize an acid that is present. Within reason, there is no possibility of having too much chalk and any excess will simply precipitate in the bath and rinse out of the fabric
Since my own broom (Genista tinctoria) is currently in need of a serious trim, I began a series of flavonoid dye tests with that and then compared other dyes from my garden and environs.
I used all fresh plants at 300% w.o.f. and dyed both wool and cotton. The wool was mordanted in alum. The cotton was mordanted using tannin plus alum and soda ash. After making the dye decoction, I divided the dye bath in two equal portions and added both wool and cotton to each bath. Chalk was added to only one of the baths.
The results were quite surprising (but also very consistent) and made me realize that I have likely not been achieving the maximum amount of color from some of my local dyes.
The plants I gathered and used were
-
- Broom (Genista tinctoria)
- Wild grape leaves
- Apple leaves
- Dyer’s Chamomile (Anthemis tinctoria). I used the flowers and after gathering a basket of the small flowers I tested the dye content in the entire plant.
- Staghorn sumac (Rhus typhena) . We often think of sumac as a good source of tannin but the leaves, according to Dominique Cardon, are also rich in flavonoids.
- Weld (Reseda luteola). This is my “go-to” yellow dye. I almost always use dried plants and I rarely add chalk with weld on cotton but frequently add it to a wool bath.
After boiling the plant material I recorded the pH of the decoction. The pH was measured again after the addition of chalk. Each dye bath was approximately 4 liters and I added about 1 TBS of chalk.
The chalk will alter the appearance of the bath from transparent to cloudy and nearly opaque.
| plant | pH after boiling | pH after addition of chalk |
| Dyer’s broom
(Genista tinctoria) |
5 | 6 |
| Wild grape leaves | 4 | 6 |
| Apple leaves | 5 | 6.5 |
| Dyer’s chamomile (Anthemis tinctoria) (flowers) | 4.5 | 6.5 |
| Dyer’s chamomile (Anthemis tinctoria) (whole plant) | 4.5 | 6.5 |
| Staghorn sumac (Rhus typhena) | 4 | 6 |
| Weld (fresh plant) (Reseda luteola) | 5.5 | 6.5 |
| Weld (dried plant) | 5.5 | 6.5 |
The samples below are wool. Individual samples on the left had chalk added to the bath. Those on the right did not.
In every case, I achieved deeper and brighter yellows colors when the chalk was added to the fresh plant baths. The only exception was dried weld, which was used at 50% w.o.f. When dyeing with the fresh weld plants, deeper yellow hues resulted with the addition of chalk. When I used dried weld plants, the chalk made very little difference. I asked Joy about this and she indicated that is was possible that some of the acids disappear in the drying process. It will require more tests and explorations to confirm this.
The cellulose samples are especially notable. The high acidity of some baths made without the chalk was enough to damage the mordant significantly. The grape leaves and the sumac, which were the most acidic, destroyed the mordant in the cellulose and only the tannins that are present in the leaf were able to attach and color the fabric.
If your water is not acidic, or has calcium in it, then these tests may not be relevant but the addition of chalk will never harm the fiber or the dye and may release more color.
I recently found the following note that I had made during a class with Michel Garcia several years ago referring to grape leaves:
“If they are too sour they will dissolve part of the mordant.” M. Garcia
My own notes continue to say:
After boiling the grape leaves the solution of a pH 4 – too acidic – it will remove the mordants. Sumac will cause the same effect. Boiling breaks the bonds of the tannins and gallic acid is released. Add chalk to the bath to decrease the acidity of the dye bath – you cannot be in excess of chalk.
Sometimes we’re just not ready to absorb information the first time we hear it. This is exactly why I continue to question, keep notes, and actively test and observe.
It’s summertime! Enjoy your yellow flavonoids!
Note: I purchase my chalk from a potter’s supply store. It is inexpensive and can be purchased in quantity. Potters refer to it a “whiting” and rarely refer to it as chalk or calcium carbonate. Do check the MSDS though, just to be sure.
Upcoming: On July 13 I am presenting a Zoom webinar, entitled Colors from the Garden, as part of the John C. Campbell Folks School’s Appalachian Traditions Series. You can sign up here:
Natural Dye: Experiments and Results 