When red + white = blue. (Experiments using red cabbage to dye eggs blue)

+ =

A couple of years ago, I learned that it was possible to dye eggs blue using red cabbage.¹ Typically, we have used a variety of artificial coloring options for our egg-dying needs, whether liquid food coloring or the store-bought Paas-type kits. Last year I was determined to try my hand at doing some natural dyes with vegetables. In the end, I gave up on my plans for using onion skins or artichokes. (The water from steaming artichokes is often an intense bright blue-green, but not from the particular ones I made that day). But I followed through with the cabbage.

I had forgotten how long it took to dye the eggs, but looking back at the photos, I see that it did indeed take a lot longer than the food coloring. So be warned: The eggs took a good couple of hours of soaking to get blue.

I started by cutting up some red cabbage and boiling it in some water.²

The resulting juice was quite purple, and I was doubtful that it would produce blue. It was, however, quite pretty. (6:18 p.m.)

We dunked the first egg and let it soak. 16 minutes later, a peek showed the egg looking somewhat lilac-colored. (6:34 p.m.)

At some point, I added a bit of vinegar to the cabbage juice, inspired by the instructions for dying eggs on the box of food coloring. The purple cabbage juice turned even redder, which made me even more doubtful of achieving blueness. So I poured some more cabbage juice into another glass to have one without vinegar, and dunked another egg to soak.

Here we are, almost an hour after first dunk. Getting to be the kids’ bedtime. Time to break out the chemicals. Here’s Phoebe, squeezing out some blue food coloring. (7:22 p.m.)

I don’t have a time for when the first egg (from the vinegar mixture) came out, but it did indeed come out blue eventually. Having read up a bit on red cabbage (as one is wont to do), I had learned that red cabbage juice changes color based on pH levels. Acid leads to redder colors, and adding something alkaline, and raising the pH, should make it bluer. I then tried adding baking soda to the cabbage juice with the vinegar. The change was instant and dramatic, turning from red to greenish blue.

Here we are, hours after the first dunk. (11:27 p.m.) The two glasses show “neutral” cabbage juice (left), and alkaline cabbage juice (right). In the background are the rest of the completed eggs, mostly dyed with food coloring. (I think the first cabbage dyed one is there in the photo, too. Second row, left, behind a yellow egg.)

Here are the chemically-dyed (top) and cabbagely-dyed (bottom) blue eggs arranged together. The lighter-colored leftmost cabbage-dyed egg is the one from the baking soda solution. (Blotchiness is due to condensation that happened from putting the previously-refrigerated eggs outside for the egg hunt.)

3 of one, a half half dozen of the other.

In the process, I realized why it is that it helps to add vinegar to dye eggs. Egg shells are composed primarily of calcium carbonate. Calcium carbonate is commonly used to neutralize acidity and raise the pH level: it is the main ingredient of antacids such as Tums, as well as agricultural lime. Acids can dissolve calcium carbonate. I’m guessing that adding vinegar starts to break down the egg shell, allowing the color to permeate and bond more quickly to the shell.

This would explain why the redder cabbage juice with added acidity led to a bluer shell (or got there faster) than the bluer-appearing cabbage juice with baking soda added.

Future study:
This year, I’m hoping to try the cabbage dye again, and also to experiment with beets, carrots, berries, and turmeric. I also may play around with acidity levels of the dye solutions again, as well as using brown eggs in addition to white. I wonder if pre-soaking an egg in vinegar would make it more permeable to dyes. (Did you know that you can dissolve the shell off an egg with vinegar? That’s another science experiment for us to do.)

Can you tell I’ve been wrapped up in academic writing? I need to get to bed.³

More resources on using natural food dyes for eggs can be found at various places around the web:
Natural Easter Egg Dyes on about.com, Making natural Easter egg dye, Three ways to dye eggs, Natural Easter Egg Dyes

Here are all of the photos from above, plus a few more.

This slideshow requires JavaScript.

¹ I think it was from NotSoSage, who sadly, has purged her blog archives. I’m pretty sure she also made red/purple eggs using red onion skins.
² That’s not entirely true, I started by buying a red cabbage. And there were steps leading up to that as well. I had to get up in the morning, for example. Sometimes that is the hardest step.
³ Seriously, I need to get to bed.

15 thoughts on “When red + white = blue. (Experiments using red cabbage to dye eggs blue)

  1. I love this! Everything about it! From the format of the post to the pictures to the pontificating!

    But, I do have a question: did you eat the cabbage?

    1. Thanks, Sally! I didn’t intend to write a pseudo-academic paper, but when I went back to put in some section headings, I realized that I subconsciously had structured it that way. I think my favorite part is the abstract.

      And, no, I absolutely, emphatically did *not* eat the cabbage. For one thing, I think boiled cabbage is gross. I like to eat cabbage, but only when it is still crunchy. This stuff was soggy, since I intentionally boiled the crap out of it. Also, in the end, I also added baking soda to the pan of cabbage. It turned this bright, toxic-looking turquoise. Certainly not something to be eaten. (I do regret that I didn’t get a picture of that, though.)

  2. Fascinating!! I love the format too. And as a painter, I’m interested in natural dyes — but too lazy to make them myself. ;) I still have fond memories of the pseudo-18th-century diary I made in middle school, though, whose pages my mother and I dyed with coffee. Every time I opened the diary it wafted an interesting old-coffee fragrance at me.

    1. Thanks, satsumaart!

      I’d like to play around more with natural dyes, too. Cool about your old coffee-scented diary. (On a tangent, I once used tea to stain strips of cloth for my mummy costume. I used lapsong suchong, which had quite a strong smell! I hadn’t considered coffee as a stain for that.)

    1. I’m not sure if everyone does the same thing with them, az. We have done an egg hunt on Easter with them, usually out in our front yard. I know that a lot of people just use plastic eggs for egg hunts these days, but I’m a traditionalist. At least about eggs.

      After the eggs are hidden and then found, we end up eating a lot of things with hard-boiled eggs for the next few days: egg salad, devilled eggs, and hard-boiled eggs straight up! Then we get sick of eating hard-boiled eggs.

  3. you’re so cool.

    onion skins are fun to use – slip the papery skin off the onion and wrap it around the egg. secure with rubber bands and THEN boil. they come out in a nice mottled yellowy-brown or reddish-purple.

    1. Thanks, Magpie. Your pretty darned cool, yourself!

      I will have to try onion skins some day, but I think maybe not this year. We’ll see…I’ll keep you posted!

  4. We always just used the packaged pellets and I would have been happy. My daughters, however, had to experiment with colour mixes, overdying and other delights, all of which ended up with the kids much the same colour as the eggs.
    My favourite, time permitting, is to blow the eggs, wipe them down with vinegar and decorate them with paint. The vinegar wipe allows the paint to stick.
    Wonderful post. Love the way you structured it.

  5. Vinegar is needed for the artificial dyes because they are acid dyes, the same stuff used to dye wool fiber and cloth. Acid dyes only bond to protein fibers when at a low pH. It really doesn’t have anything to do with the calcium of an eggshell. (yes you can dye animal fiber yarn or cloth with artificial easter egg dyes)

    Shifting the pH of many natural dyes will weaken the dye. Doing this same experiment with cloth, you will see a similar result. A baking soda – red cabbage dye on silk or wool will be paler than if the pH is neutral. Again, nothing to do with eggshells. :)

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s