Much of the conversation about indigo is about the need to tend it. “They Say” to stir it daily, test for Ph, keep it at a constant temperature, and on and on…
And Yet: my 30 gallon organic henna vat hibernates like a bear through the long, frigid winter in northern Wisconsin. In the fall, I add a good dose of henna liquor* and a bit extra lime, give it a loving stir, and cover it tightly. Our garage is heated on occasion, yet the temperature hovers mostly between -20 and +10F for four months.
This spring, I took the cover off, stirred, added lime, added some warmed henna the next day, and once a week stirred and checked Ph. When I wanted to use it, I added some fructose (like coffee does for me, it gives the vat a jump-start) and was rewarded with a darker blue than I had last fall!
This vat has happily performed all summer with only occasional stirring, and adding lime and/or fructose.
*henna liquor: mix henna powder in enough water to make a pea-soup-like consistency. Bring to a gentle boil, and shut off the heat. Let the mixture separate and decant off the liquid. Repeat several times, adding more water to the paste. After 3 times, dump the henna solids in your garden! Keep refrigerated until use. Warm before adding to indigo vat.