FEEDBACK FRIDAY: This Week in Natural Dye Questions

This week: Making a powerful indigo vat for a 5 gallon bucket

Every week, we are emailed with questions from our natural dye community asking simple and complex questions that we thought might be worth sharing. Of course, all of your burning questions are answered by natural dyer in chief, Kathy Hattori, Founder of Botanical Colors.

I’ve been working with your organic indigo to make fructose vats the last couple of years. Can I ask how much indigo you recommend to achieve a dark color blue, dyeing from a 5 gallon bucket sized vat? I’ve made what I think is a very concentrated vat (24 tablespoons of indigo, 1-2-3 method) but just can’t seem to yield a dark blue and it takes at least 8 dips of increased time periods starting with 5 minutes and building up to over an hour for the final dips just to get a medium blue color. Is this to be expected?

I’m estimating that your 24 tablespoons of indigo is about 250 grams of indigo. Is this correct? If so, that should create a very dark vat with 1-2 dips. Here’s some information to help achieve dark shades.

1. Use between 100-200 grams of indigo for a 5 gallon bucket. Vat temperature should be about 90F if possible, but a cooler vat also works.

2. Stir the indigo very well to mix in the sediment at the bottom. Create a vortex, then let settle and the vat liquid turn clear, not murky. This is important because some amount of indigo has settled to the bottom of the bucket and you want to re-introduce it into the vat liquid.

3. Observe the indigo flower: are there a lot of healthy, dark purple-blue shiny bubbles? Or are the bubbles somewhat light or medium blue or very scant?

If the bubbles are light, then add fructose or henna to the vat, stir well and let settle to reduce and balance it. If it still yields pale shades, then add more calcium, stir well and let settle. We find that it’s easier to add a little dissolved fructose, even to a henna vat to restore its balance.

If you’ve dipped a lot of fibers (4-10 lbs total or more), then you will need to add more indigo.

We just built a henna vat at Haystack Mountain School of Craft with 160 grams of indigo, 320 grams of calcium hydroxide and 480 grams of henna, and we were able to get dark colors with 2 dips. We modified the 1-2-3 recipe and used very hot water (150-160F) and also dissolved or wet out all the ingredients in separate containers. We did not use the mason jar method, mostly because our quantities were too large. We then combined the ingredients one at a time into a bucket half filled with very hot water (160F), topped off the vat with more very hot water, stirred well for 3-5 minutes, created a vortex, then let the vat settle and cool for several hours. The vat had an enormous, dark purple-blue flower, indicating a healthy vat and the color was good.