|The chalk-like sediment is visible when you stir the indigo adding to the guesswork of the condition of the vat.|
It is not desirable to make a new vat every few weeks because there will be a reasonable amount of precious indigo pigment thrown away with the water as well as being a lot of work. When you stir the indigo and feel the sludge at the bottom of the vat building up, imagine what is happening down there in the deep blue. The above mentioned whitish-green cloud in the freshly stirred indigo is also an indicator that it is time to go through the hassle of cleaning up the vat and starting fresh.
Of course the vat will have usable indigo pigment in it. The trick is how to exhaust the pigment effectively and properly.
There was no denying yesterday that the ceramic vat outside the front door needed re-done. Liza dropped in a piece she was dying. It floated to the bottom and when I retrieved it it was covered in deep-sea indigo monster mucus.
There were three more kilograms of red cotton thread to over-dye with indigo sitting there. They were put in the bath tub after the humans were finished last night and this morning they were well wet enough to dye. The indigo vat in question got a good spiffy up with a topping off of water, the pH adjusted and a good hit of hydro-sulphate and a strong whirlpool stir before bed. The sediment had all settled by morning and the thread was dyed gently five times until it was obvious the pigment was nearly all soaked up.
Thank you indigo vat. I set this one up with Eri chan one cool November morning a year and a half ago. It had been very well used.
I threw in an old Snoopy blanket to suck up as much pH as possible and then hung that in the sun to dry. It will get thrown away with the regular garbage and they can burn it with the filter at the garbage dump. The exhausted dye bath was drained onto the gravel near the stream. Not strictly the most environmental thing to do but I worry that the sudden pH shock will kill the bacteria in the new state-of-the-art septic tank that was just installed.
The sludge at the bottom of the vat was scooped out and spread thin on a piece of plywood to dry in the sun. That will take a few days and then it will be scraped up and put in a plastic bag and thrown away in the regular garbage.
The work involved in keeping a indigo vat going over a long period of time is daunting whether it is a fermentation vat, a hydro-sulphate vat or a zinc vat. (Jean I think of you!) Any questions just ask.