A question came up recently in one of my classes that I don't know the answer to but would like to!
The question is "Does thiourea dioxide buildup in indigo vat over time to an extent that the vat needs to be disposed of and the vat remade? Or does the thiourea dioxide exhaust over time?"
As long as the vat is dyeing well and ingredients properly balanced my vat seems fine (over 2 years now). I have of course added water, indigo and all other chems as needed but I have heard that one needs to dump it every now and then (when?). I like to know the chemistry behind such statements but often these things are said/posted without such info whether or not they are true.
Nice to know I can come here and ask the question when I am lacking in the chemical understanding of it all.