Dyeing Protein Fibers in a Natural Indigo Vat

Q: I’ve heard I cannot dye protein fibers like wool or silk in an iron vat, is that true?

A: You CAN use the iron vat for protein fibers, but when I do, I make sure that I do two things:

First, I make sure that the fibers NEVER touch the sediment at the bottom of the vat. The sediment contains a lot of iron which will bond to the protein fiber and cause the indigo to look dull and flat.

Second, I make sure that I rinse my pieces in acidic liquids immediately following each dip. Water with a little citric acid powder (half teaspoon per gallon) or a quarter cup of vinegar for about 4 gallons of water, works well. Ferrous vats have a high pH and animal fibers prefer a low pH. The high pH of the vat will break the protein chain and the fibers will feel scratchy or lose their luster if they are allowed to dry after coming out of the vat without being rinsed in an acidic bath first. I also soak protein fiber pieces in a mild vinegar solution overnight after dyeing and prior to washing. I’ve also heard, though never done this myself, that a little hide glue added to the vat will help keep the fibers in good shape.

If dyed properly, a ferrous vat will create beautiful blues on protein fibers. The ideal vat style for protein fibers is the traditional fermentation vat which is fed by decomposing plant matter, wheat bran and oxygen (from stirring) but is very challenging to execute on your own without guidance or experience. You can also look into a fructose vat or thiox vat for other options. Maiwa has a great PDF on different vat recipes here: https://naturaldyes.ca/indigo-pdf.