This afternoon I made the vat according to Garcia (his proportions, my quantities):
1 teaspoon of indigo - I used Pure Tinctoria powdered extract
2 teaspooons of calcium hydroxide
3 teaspoons of fructose
The teaspoons were level and the vat is a large Kilner Jar.
The pH was 11, as recommended by Garcia
Within 10 minutes the vat had gone from grey through green to yellow
By 25 minutes, there was blue foam forming on the top and a coppery scum developing - much like my rising levels of excitement!
After 30 minutes the foam had turned dark blue
Left: Vat at 25 mins, Right at 45 mins containing cotton
At 45 minutes, the vat should be ready, according to the instructions. The pH was still 11 and remained at that level throughout the dye session.
I put in a cotton wool ball and a piece of cotton in the vat which now had the sherry colour that one expects from woad
The first dip, airing
Third dip for cotton and second for linen
All in all, very successful and the vat is by no means exhausted, so I will go on until one of us gives up! What I'm not sure about is how to revive such a vat - there's no problem with reviving more usual vats. I warm them up, correct the alkalinity and put some reducing agent in and they come round. This will need some experimentation, I think