At this time last year, The Art and Science of Natural Dyes (Schiffer Press) was published. Joy Boutrup, my co-author, and I submitted the completed manuscript almost two years ago. During these last 24 months I have been teaching, traveling, and continuing to work in the studio. We have heard from many of you and appreciate that dyers are actively using the book. I’ve tried to respond to the numerous questions and comments that have come my way.
I continue to learn, and plan to publish a series of posts that will reflect some of the lessons from the dye studio that have revealed themselves in the last months.
Today I want to share issues with indigo and crocking.
A couple of years ago, I took up knitting…once again. I dyed yarns in my 30 gallon indigo vat reduced with henna. This vat has been dyeing well for approximately 3 years. I came directly in contact (no joke) with the crocking issues of indigo. Crocking occurs when excess dye rubs off onto another textile or on the skin. My knitting yarns had been dyed well, neutralized, finished by boiling and yet still they crocked. Because of the handling of the yarns, knitting reveals rubbing issues that are easier to ignore with other dyeing projects.
This has started me on a long, involved exploration of indigo vats that has taken me in many directions.
Indigo does not attach to the textile in the same manner as mordant dyes, so I think that some crocking is inevitable when dyeing with indigo but I wanted to see if we could decrease the amount of crocking on my yarns.
I suspected that part of the problem was the high quantity of lime (calcium hydroxide) in the henna vat – or in any of the quick reduction vats. Joy also believed that the calcium binds to the indigo, making it more difficult to remove from the textile.
The first thing we explored was a more thorough washing of the dyed textile. Usually I finish all textile with a neutral detergent but a mild alkaline soap is particularly effective in removing excess dye. In order to be effective, the soap must be concentrated enough to foam up when heated. We soaked the indigo dyed textile in a mild “Ivory Soap” solution. We watched and saw that more of the excess indigo released from the textile in the soap solution than with a neutral detergent. The challenge when using soap is that it does not rinse out, leaving a fatty substance behind that would make mordanting and over-dyeing problematic. We used a heated Metaphos (phosphate) solution to remove the soap. But we saw no difference in the crocking after this treatment.
Next, we experimented with substituting lye (sodium hydroxide) for the lime (calcium hydroxide) in both henna and iron vats. Joy determined the amount the lye required, based on the molecular weight. We substituted 1.3 grams of lye (sodium hydroxide) for 1 gram of lime (calcium hydroxide).
We often think of lime as being benign because it can be purchased it in the grocery store as “pickling lime” but it is a very strong alkaline and we need to be careful with both of these substances.
While teaching at Penland School of Crafts last summer, Joy and I made two 5 gallon vats with the class, using lye with henna and iron as reduction agents. Initially these vats worked very well and there was an added benefit with the lye: no calcium sludge in the bottom of the vat.
The vats made with lye seemed to significantly decrease the amount of crocking but I did find the these vats more challenging to keep in reduction for long periods of time than those made with lime. The pH had to be watched more carefully, as the henna vat would go out of reduction when the pH went below 12 and required boosting with more alkaline. I do believe there is potential to make these “lye” vats work well, but my own follow-up experiments were done with small 2 liter vats and I never scaled these vats up. The truth is, I got distracted by fermentation vats, which have long been on my own list to explore.
In my next post I will share some of what I have learned about fermentation vats.
Coming up: The North Carolina Arboretum will host the third Growing Color Symposium in Asheville March 11 & 12, 2020. Presenters include Sally Fox, Sara Bellos, Donna Hardy, Rowland Ricketts, Dede Styles, and myself. Rowland and I will teach a workshop on the indigo vat and Sarah Bellos will be able to update us on Stoney Creek Colors and their indigo harvest and extraction. Donna Hardy will also do a post symposium workshop at Cloth Fiber Workshop. Do come if you can!