A deep blue-black dye. This is the synthetic version of the natural indigo. We've included it separately here since it is listed on tubes sometimes as VAT Blue 1. However sometimes it is listed as Synthetic Indigo, PB66. Reports conflict on its lightfastness, and some say that natural indigo was less lightfast. However, it is fairly easy to mix a range of indigo colors which are lightfast, so its appeal is probably more for those who wish to paint with it for other reasons.
We were super surprised to hear about its toxicity.
