Friday, February 26, 2010

Dyeing cotton with natural dyes

I'm teaching a second indigo dye workshop with the Sunshine Quilters this Spring. Natural indigo dyes wool, silk, linen and cotton equally well. But instead of indigo they want to add a mordant dye to their repetoire. The goal is blue from indigo and green using a yellow overdye. So I am needing to plunge in and learn to dye cottons with natural dyes. This is something I've avoided as it appears that it is terribly fickle and subject to many failures.

I started my quest with rereading Jim Liles book, The Art and Craft of Natural Dyeing, traditional recipes for modern use. (highly recommended if you are dyeing plant fibers)

I learned that I need to scour the cotton fabric more diligently than I do wool, to get out the cotton seed oils and sizing. Then I need to mordant first with Tannin -- 1 1/2 ounces per lb. of fabric. That's about 2 tbsp. by volume. Tannin is mordanted cold. The fabric is worked through the vat and then it is left for 12 to 24 hours to absorb. The next step is an alum mordant -- using washing soda instead of citric acid, again, colder than for wool and again a long soaking. And 8 oz. per lb. of cloth. Yikes! That's like 50% weight of goods! I started with 4 oz. if it doesn't work I'll try 8 oz. next time. Then you need to get the excess mordant off the cloth before dyeing.

After the tannin the cotton fabric has a pink hue. Some of it changed to buff after the alum soaking. I think you might want to use myrobolan rather than tannin if you're after a green in the final hue, which we are. Myrobolan is a yellow dye rich in tannin that is dyed cold. It will leave a yellow hue which may/ or may not turn green in the indigo vat.

We will be using a chemical indigo vat which tends to strip off any previous colour before laying down the indigo. Not sure if it will work like this on natural dyes, though. Experiment!

Since the project is a shibori project, I have my fabric in 9 inch strips, cut the full width of the fabric bolt. I think this will be easier to dye in the indigo vat without so much white area. My project will be a shibori sampler with several techniques demonstrated on the strip. I think the quilt guild wants to dye fabric for quilting so will probably only adopt one or two shibori techniques per piece of fabric.

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