Dark indigo

29 August 2006

I received this email:

hi! i followed your instructions for an indigo vat and it reduced perfectly to a yellow color and i was able to dye my shirt evenly with no trouble.
however, i wanted a REALLY deep shade of blue and found that I had to dip the shirt about 15 times to get the color I needed! and even then it wasnt as dark as I wanted. in between each dip i let it hang outside and air out for about 20 to 30 minutes, and eventually I started rinsing it after each dip to try to build up the shade.
if i were to double the indigo in the recipe along with the lye and thiourea dioxide (but keep the water the same) would this allow me to get a deeper shade with minimal dips?
i understand that the chemicals would make the solution more harsh to the fabric and irritating to the skin – but I am only dying 100% cotton fibers and i will wear gloves.
have you ever tried this?

Indigo is not an easy dye to work with and I congratulate on getting a dark indigo color. Try more indigo in the pot!
Darker indigo colors are very prone to crocking. Going slow and building up the layers slowly, up to 30, are used to get a non-crocking deep, dark indigo color. The indigo in the dye pot needs to be replenished as it is used up.
Not every one cares about the crocking and in that case a dark color can be achieved in 3-5 dips. It is always a compromise, fast vs. crocking. Here are directions for a large fast dark vat.
There are many ways to make an indigo vat, and this one has salt. The Japanese advocate, 30 dips and 24hrs. airing between dips (even so they have an abundance of dark indigo dyed textiles). Another source of info on an indigo vat is ProChem.
Finally I wash the indigo dyed piece in the machine with Synthrapol . Then I neutralize the alkali with an acid, tannic is my preferred one as it tends to darken the color. I boil up a pot of tea and keep the goods in it for a while, hot. This tells me if I’ve done a good job of washing also, if the tea turns blue it needs more washing. There are other post-treatments, with things like hide glue to reduce the crocking but I have less experience with them.
I use gloves because I don’t want blue nails , a common occurance in traditional indigo dyers.
I hope this helps.


One Response to “Dark indigo”

  1. Peggy Gaillard Says:

    I brought back a bag of powdered indigo from Egypt. They use it to whiten their clothes. I would like to do the same. Any hints on how much to use? Peggy


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