FEEDBACK FRIDAY: Indigo Painting + Indigo Vats

Indigo Ink SetThis week: Indigo painting and temperamental indigo vats

Every week, we are emailed with questions from our natural dye community that are worth sharing. Of course, all of your burning questions are answered by natural dyer in chief, Kathy Hattori, Founder of Botanical Colors. This week we look at Indigo painting and temperamental indigo vats.

I am trying to paint cotton fabric with the indigo dye ink I purchased. I thickened with Gum Arabica and all looked great, but it washed out after drying. I tried spreading soy milk first, let dry and then painted. It didn’t help. What do I need to do? I would like to use these cotton squares I am painting (drawing) for quilting with my dyed indigo fabric.

The indigo ink is an ink, meaning that the color pigment can only bond with the fiber on the surface as the dye molecules are not soluble to bond into the fiber like with an alum mordant. Its intended use is as a drawing ink on paper. If you are thickening with Gum Arabic, that is fine, but then you need some type of bonding mechanism. A bonding agent like soy milk should work and you might need to add some soy milk into the ink itself to assist the bond. However, once you have done this, I don’t think you should wash it right away as it is not a very strong bond.

You can make the soy milk bond stronger by curing or air-drying the piece for several weeks (keep away from direct sunlight). This helps the soy bond strengthen. I have not tested this, so can’t tell you if it will work like you are expecting or not, but I have painted with indigo pigment using soy milk on the fabric and in the ink and it worked well. I hope this is helpful to you.

I am trying to create my first indigo vat. I started with 3 heaping tablespoons of Stony Creek indigo and repeated this process three times and could not get it to work. I thought that I may not have been measuring correctly, because the indigo heaped up a lot on the spoon but the fructose slid off into a more even tablespoonful.

Then I restarted the whole process with much more precise measuring: I used 100 grams of Stony Creek indigo and 200 grams of calcium hydroxide and 300 grams of fructose in a 5-gallon bucket. The pH was 13 and very few bubbles were formed, and there was no reduction after leaving it overnight. I tested the pH which was still 13. After that, I added 2 exact tbsp of fructose which made a few more bubbles. After an hour, I added 2 more tbsp of fructose being very careful and adding a little at a time. I then added 2 more tbsp after 3 hours and left it overnight. My question is what happens if I put too much fructose in it? Should I put more in each time? Can I kill the vat with too much fructose? Oh, and I heated the stainless steel pot of water up to 120 degrees and stirred well but gently each time I added something to it.

You are on the right track. The 1-2-3 indigo vat reacts a little differently to each vat maker. Please don’t throw anything away – you can use all of this in your indigo vat.

Follow these steps:

1. Reduction is going to look like the following: oil slick on the surface of the container and some bubbles. Adding fructose usually generates more oil slick and bubbles because it’s the reducing agent. The liquid should look green, or sometimes like a light brown beer color. If you can’t tell by peering into the bucket, carefully dip your spoon in the liquid and look at it in the bowl of the spoon. If it’s dark blue, it hasn’t reduced. If it’s greenish or olive-colored or brown beer colored, it’s ready. If it’s still dark blue, then you can add a lot of fructose (like 250 grams or more), especially since your pH is 13, so you know you don’t need to adjust the amount of calcium hydroxide.

2. If you put too much fructose in, your solution will be over-reduced and it would appear very yellow – like urine. I have never seen a 1-2-3 vat get to this condition, so I would not worry about it. If that should ever happen, then stir the vat well to incorporate all the sediment at the bottom, and start whisking it to incorporate air into the vat, and the fructose over-reduction will start to balance and the solution will turn greener or browner. If it goes blue, then that’s too much air and you would need to reduce again.

3. Stony Creek is a grittier variety of indigo, so I’ve found that it incorporates more slowly than our other varieties. You may need to wait longer to see the reaction as the granules of the indigo are larger and a bit more “impermeable.” It also dyes grayer than our other indigo varieties, but it is a very pretty blue.