Indigo Dye with Dates

Did you know you can make an indigo vat out of those pitted dates at the grocery store?

You’ll need the 12oz pitted Medool dates, and you can get them at HEB or Costco. You’ll need some indigo powder as well, of course, and some calx (calcium hydroxide).

Other equipment you’ll need to gather:

• a scale that can measure in grams,
• a saucepan,
• something to strain the cooked dates with,
• a dust mask,
• a 5-gallon backet,
• another bucket to hold some cold water, and
• a long handled stainless-steel spoon (or a wooden one you don’t mind it turning blue).

Some pH test strips will also come in handy if you plan to keep the vat going for a few more dye sessions, or if you want to swap between dyeing cotton and wool.

This will be a small indigo vat. You can always double the measurements.

Chop up and then cook the dates. Cover the chopped dates with water in a big pot, bring to a boil, and then simmer for 30 minutes. Take it off the heat and let it sit overnight.  The next day, filter the mushy dates through a sieve and keep the juice. Compost the rest.

Take half the juice and set it aside for later maintenance of your vat. Pour the rest in a 5-gallon bucket. Fill the bucket to about ¾ full with hot water. The hottest from your tap is fine, but you can add a little bit from a tea kettle or saucepan that’s not quite boiling.

Wear a dust mask (or you’ll end up breathing in the indigo and/or the calx – both are super fine!) Weigh out:
35 g powdered natural indigo
35 g calx (calcium hydroxide)

Carefully sprinkle the indigo on the surface in the bucket.

Now you’ll need to stir your vat, but you want to do so in a way that doesn’t introduce any air into it. (Or send the indigo and calx flying.) Think of a witch stirring her cauldron – you want to stir in a kind of whirlpool motion. This video or this video should help you see the technique.

Once the indigo powder seems all wetted out (it will NOT dissolve), carefully sprinkle the calx across the top. Stir, again being carefully not to send the powder flying or introducing oxygen into the vat. Keep stirring until all the indigo and calx powder are mixed into the water.

That’s it! Wait about 5-10 minutes and stir again. Another 5-10 minutes and stir again. You’re lifting the indigo and calx powder from the bottom of the vat where it’s settled and getting it back in contact with the fructose from the dates. That’s where the reaction happens to change the indigo from an insoluble (can’t dissolve) pigment good for painting canvas, to a soluble form (a chemical reaction called reduction has happened and now the indigo is part of the liquid) that’s good for dyeing cloth.

After another 5-10 minutes, give it one good final whirlpool stir and then cover the bucket (with a towel, a plate, a piece of cardboard – or the bucket lid if you have one) lightly and let it sit overnight.

It should be ready to use after 24 hours. Be aware that sometimes it’ll take less, sometime longer (like 2-3 days). You’ll know it’s ready when there’s a bronze-y colored sheen on the top that looks like an oil slick and a frothy “flower” of indigo on top. Use a spoon and push apart some of the slick. It should stay separated. Scoop a little liquid into your spoon. It should be a clear deep amber color.

You’re ready to dye!

Have another bucket of cool water nearby. You can dip your scoured cloth (make sure it has no oils or waxes on it that might keep the indigo from penetrating) into the vat, and keep it under the surface, gently massaging the liquid into the cloth for 3-5 minutes, depending on the density of your cloth. Gently lift the cloth out and squeeze the excess liquid off near the surface of the vat and turn some of your precious liquid indigo back into a pigment.

Open up your scrunched up cloth and you can see the change from the greenish amber start to blue happen right away. Go ahead and plunge it in the bucket of cool water to rinse off any excess liquid that didn’t penetrate the cloth and any of the mashed date gunk. Squeeze the water out, and let it air out for about 10 minutes. This will let the indigo fully oxidize – i.e. turn back into a pigment in the cloth.

Repeat the dip, massage, rinse and airing three to five times. That will create enough layers on your cloth to protect it from fading. Then let your project dry overnight. It will dry a slightly lighter shade than when it’s wet.

BTW, avoid doing protein fibers like wool and silk right away since the pH of the vat is too high for these. Start with cotton and, when the pH drops to 10, you can do some wool. Alternatively, give the vat some of the reserved date juice, stir it and let it rest overnight. Keep doing that for a few days until the pH drops to 10.

Yes, you can dye yarn too. Just open up your skein and tie some figure-eight ties around the yarn in about four places. That’ll make sure the dye can easily flow around all the fibers, but while keep the yarn from tangling.

After your final dip and oxidizing, let your cloth rest in a bucket of cool water and ¼ cup of vinegar. This will neutralize any calx left on the cloth, which could lead to fade lines later, especially in folded areas.

Good luck! And if this sounds fascinating, but a little overwhelming to try yourself just yet, then come to the annual studio tour in November and see how it’s done in person.