Like alizarin, indigo is a dye that we used to have to rely on a plant to make. Now we're able to synthesize it:
Indigo used to be prepared from natural sources, like plants. Modern synthetic techniques have made it cheap and plentiful. While this might seem like not such a big deal, can you imagine a world without colorful...well, much? Everyone wearing Amish white and dishwater grey?
Nowadays, we tend to use dyes that have nothing to do with plants, like Yellow 5, Red 40, and Blue 1 (the separation of which you can see here). Dyestuff technology has advanced with synthesis and physical chemistry, and we now have dyes that are designed to be used in lasers or to detect radiation, and dyes that can sense polarity.
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By Joe Schwarcz, Author, USASEF Expo Performer, AT&T sponsored Nifty Fifty program speaker & Director, McGill University Office for Science and Society - Montreal, QC, Canada
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Try to find a jet black full length lab coat. Good luck. A real man would custom-sew it out of black velour (maybe with a painted portrait of Emil Fischer on the back).
Doing it at home requires a 100% cotton lab coat and a half pound each of jet black fiber-reactive dyes Cibacron-F (hit it hot and hard with double the salt - not iodized!) then after washing and drying Procion-MX (run that at least very warm, double the salt). Gradually add sodium carbonate solution with strong mixing after dye saturates cloth. Each stage is a grievous massive mess. Your 5-gallon polypropylene bucket will be stigmatizedalong with your patio. No wonder dyers were Untouchables at the edge of town.
http://www.dharmatrading.com/
good stuff at fair prices
Indigo is not lightfast. If you want kick-butt blue go 100% polyester lab coat and disperse dye with Foron Brilliant Blue - blue so blue it hurts to look. Foron will get you picked up by UFOs.