Wednesday, November 16, 2011

Indigo-go or Stand Back, I'm Doing Science!

The first class I took at Kid 'N Ewe was dyeing with indigo. I had no idea that it would appeal to my love of chemistry. This post is a bit heavy on the science, so if you are truly science averse you should move along, for those willing to stick it out I promise pretty pictures along the way.

The major issue with indigo dyeing is that indigo is not water soluble. So you have to mess with it’s chemistry in order to use it. First you take the indigo powder and suspend it in warm water. This is referred to as indigo paste, but, while I understand it’s a defined term so there’s no reason to argue with it*, I think it’s too liquidy to call a paste. Then you take some hot water and add an alkali and a reducing agent** to the mix to create “indigo white.”

Do not boil indigo!
That's Christine from spinning straw into gold, teaching us not to boil indigo. The temperature needs to be hot but not boiling (around 120 degrees Fahrenheit, do not exceed 140) for the reaction to be happy. After allowing time to pass for the reaction to take place, you end up with something that looks like this:
Green/brown? I thought indigo was blue.
The stuff on the top is called “the flower” which is essentially unreduced indigo. (This is where I get to say one of my favorite chemistry jokes: If you’re not part of the solution, you’re part of the precipitate. I didn’t make it up; I wish I had.) If we were going to be very careful about what we were doing we’d scoop the flower off so that the unreduced indigo doesn’t cause crocking.***

We tried both organic and chemical dyeing. The reducer for the chemical was hydrosulfite, the alkali was lye; in the organic vat the reducer was fructose and the alkali was pickling lime. I love the idea of using organic sources (knowing how to do something in a post-apocalyptic world/learning how something was done pre-industrial age is fun), but you can get predictable results if you know exactly what you have in a solution.

In order from left to right: organic made the day before, organic that day, chemical the day before, chemical that day.
 As you can see the indigo "white" can range in color from green to amber. Pour your solution of indigo white into a vat that’s been prepped with a bit of the alkali and reducer. We decided to use the organic one Christine had made the day before, and the chemical we made in class.

Not pond water.

I know it is green; I swear it dyes things blue. Let it sit for fifteen minutes to four hours. There seems to be a lot of waiting for stuff to react in indigo dyeing. If you are in a hurry, although I’ve not tried them yet, I think Kool-Aid or acid dyes are probably going to be your best bet.

Then you put on your dish washing gloves, or borrow them off someone else if you didn't bring your own, and dunk whatever it is you are going to be dyeing. If you are using the organic vat you want to hold it above the bottom of the vat (there’s icky stuff at the bottom) but completely in the solution so that the dye permeates equally.  In the chemical vat you can drop your item off and have a cupa, as long as your cupa takes less than two minutes. The vat is rather alkali and if you left it in there for long it would end up destroyed.

When you take your dyed thing out, it’s kind of an ugly green color. As you open it up and expose it to the air you can watch the blue spread across as the extra hydrogen atoms in the indigo white react with the oxygen in the air returning it to indigo. It's really cool to watch.

Hang your items to try for 10 to 15 minutes then repeat the dunking until you attain the blue you are looking for, or until class is over. You must dunk your items at least twice in order for it to be chemically stable.

The lighter ones were dyed with the organic dye.
 We attempted to dye silk and wool fibers and found that the silk takes dye like fish takes water, while wool is not a fan.

They were all dunked once, but look at the range of colors.
You have to be sure that your vats aren’t too alkali (you are looking for a PH of 8 to 10) or you’ll end up stripping the dye as you are adding it. Kind of like when you try to add a second coat to your nails while the first coat of nail polish is still wet.

We put our finished pieces in plastic baggies full of water for transport. Once I got to my sister’s place, I poured some white vinegar in to neutralize the base and then hung it to dry.

 I was planning on giving this scarf away at Christmas, but I’m having a hard time giving it up. I think this class was the one I most enjoyed, but I’m probably not going to set up an indigo vat at home. Well, not yet.

*I dislike terms that are misleading. Atom means “cannot be broken” so how do you have sub-atomic partials? I know atom is now the word used for “the smallest particle of something that is still that thing.” But if you are going to use that explanation then what is the difference between a molecule and an atom? The molecule of indigo is the smallest part of indigo that is still indigo. I think they just got all excited and named things atoms too quickly. Okay, rant on poor naming conventions over.

**Reducer in organic chemistry means something adds hydrogen atoms to a molecule. In the case of indigo two hydrogen atoms are added to make indigo white. See above rant.

***Crocking is where the color rubs off of something dyed. The way to fix crocking for indigo is to place the item in a water bath with a little bit of alkali and a little bit of reducer mixed in. That way the unreduced indigo gets reduced and attaches itself.


Erin said...

Really dug this one. Very interesting and I'd love to do indigo dyeing some time. Also, that scarf is pretty amazing.

MaryAnne said...

I had no idea indigo dye changed from green to blue like that. Now I want to try - some day...

The scarf is awesome!