Indigo Vat Dyeing Day
I waited all weekend for the good weather and finally Monday was a nice sunny morning perfect for beginning my indigo vat.
I began by making a discharge bath and removing colour from half my woven shibori sample. Once the day warmed up I began the indigo vat. The instructions in Jenny Dean’s book and from fibrecrafts.com are what I followed, having made up a stock solution last week.
I used tap hot water for the vat (a stainless steel pot), tested the temp. and the Ph and added soda ash, the temp. was good at around 45C. The tap water goes through a softener and the ph is between 6 & 7 and so I added 2 tsp. of soda ash to 8 litres of water which brought it up to ph 11 which is about right I think from all the various sources I have been reading. I added a teaspoon of thiourea dioxide, let it sit a few minutes and lowered my jar of stock into the vat and let the solution run out leaving the layer of undissolved indigo at the bottom. At least that is what I think it must be and I did dissolve it later to add to the vat as it runs out of indigo.
Then I waited – readings suggest anywhere from 10 min. to 45 min. I waited about 20 min. The colour looked right, a sort of clear green though it was darker looking than photos in the book. I thought this might be partly the depth and size of the vat. The photo in Dean’s book is in a clear glass bowl. I tested the sample and as I pulled it out it began to turn blue! It really is exciting to see it happen. I let it oxidize for 10 min. (probably too short, but i was impatient to keep going!) and dipped again. I continued to dip into the indigo, plunge into a clear water rinse and let it rest about 20 min. between dippings.
I could see quite quickly with just a few dippings that it would take quite a bit to get the blue I wanted on the orange half of the sample. The discharged half was turning a bluer blue, so I put the tied shibori scarf into the discharge bath. It came out a yellowish colour, especially in the tied section.
Perhaps the bath wasn’t large enough for the amount of dye, but by weight it should have been fine. The sample was a little lighter, but not by much so I proceeded to put the scarf into the indigo vat after rinsing and neutralizing. I am not sure if I could have gone directly from the discharge bath into the indigo vat, but chose not to. It was suggested to me that the indigo vat would act as a discharge bath because of the thiourea dioxide being used as a reducing agent, but this didn’t happen on my sample piece. I would think that the TD in the indigo vat was used up in the indigo reduction process and also there wouldn’t have been the same concentration as a discharge bath.
Lots of untieing to do now, this photo shows the un-dishcharged side of the sample. I will begin with the sample piece and if I like the intensity of the indigo I will continue with the scarf. If not, I will dip the scarf until I get the effect I like.
I also continued with dyeing the scarf I had tried last summer in my indigo fermentation vat. My conclusion is that in my first attempt I didn’t grind the indigo finely enough, I didn’t have enough indigo in the pot, the Ph might not have been correct and that the temperature of the bath was probably not high enough.