A few words about indigo.
The most common question or concern that arises when people use naturally dyed yarns is the first time use of natural indigo dyed yarn. As knitting begins fingers turn blue as the yarn is worked on the needles. The logical conclusion is that perhaps the yarn was improperly dyed and all the color is coming off. With natural indigo this is not the case.
A few years ago I was in need of a new pair of jeans. I always purchased jeans at the Gap store because I knew my size and it simply involved popping in, grabbing a pair of jeans off the shelf and going. My preferred method of mall shopping. I wore the jeans and when I took them off the first time, I immediately noticed a blue tint to my legs. For half a second I thought I may be dying (HA) but as an indigo dyer quickly realized what it was. Synthetic indigo is still indigo. I am not certain what the process is in creating it, but after a quick shower removed the tint, I thought that I much preferred to be blue stained by natural indigo rather than synthetic. Why does this happen though?
The indigo pigment molecule is non soluble in water in its natural state. It must be altered so that it may be dissolved in water. A fish is suspended in water and salt dissolves in water, so essentially we want that fish to turn to salt and dissolve. We can either extract the molecule from the fresh leaves or use already ground indigo powder. In either case we must alter the material. The blue powder as is may be rubbed on to the skin or rubbed in to clothing, but it will wash out. At this stage it is not a dye. We must create the conditions for the blue indigo powder to become soluble in water for it to bond with the fiber or cellulose molecules.
This process involves creating a vat with the appropriate conditions for the indigo to transform. A magic potion!
There are many ways to create a vat, there are many, many historical recipes and differing degrees of tinkering and pampering involved. All of the vats need for two things to happen- increased Ph and decreased oxygen. The increased Ph or alkalinity must be at a Ph of about 10. The oxygen decrease in the vat an be achieved in many ways, depending on what type of vat you are creating. In the organic 123 vat, fruit is used to create the low oxygen environment. These conditions alter the indigo molecule in to Leuco-Indigo, which is dissolved in water. The color of the vat changes from blue to a rather dismal yellowy-green. This is a visual indicator that the vat is ready for use.
After dyeing with indigo, items are rinsed in a vinegar (acid) solution to restore neutral Ph. Rinsing removes much of the excess indigo from the yarn or garment but handling after drying will remove the rest. This is what causes blue fingers.