I find natural dyes to be amazing. I have experimented with dying eggs with natural dye for a few years.

One of the fun dyes to use is from red cabbage. Red cabbage is a natural litmus, which means it changes color based on PH (acidity or base). The color of the eggs can range from blue to green.

For this I am going to test how PH affect the color of the eggs.

Supplies

red cabbage
large knife
pot
water
vinegar
baking soda
glasses or bowls
oil (I use olive oil)
paper towel
and of course eggs. For this test pre boiled eggs.

Step 1: Preparing the Dye

To prepare the dye, you will need a head of red cabbage.

Chop up the cabbage into coarse pieces. You won't need the whole cabbage, but you can also use the dye for science experiments or make green eggs and ham (reacts with the egg whites). Once the cabbage is chopped, add it to a pot, add water to the top of the cabbage and simmer until the cabbage is soft and the water has a deep color. At this point drain off the dye.

Step 2: Dying the Eggs

To hold the dye, I used 5 plastic cups and a bowl, each cup had a 1/2 cup of dye and an egg. To the bowl, I added about 4 tablespoons of vinegar. To cups I added either vinegar (an acid) or baking soda ( a base), to see how they affected the color. What I added to the cups from right to left was 1 tablespoon of vinegar (far left), 1 teaspoon of vinegar, 1/2 teaspoon of vinegar, 1 teaspoon of baking soda and the last one on the right was only dye as a control.

The cups with vinegar turned pink, while the cup with the baking soda turned darker blue. I let the eggs soak overnight in the refrigerator.

In the morning the dye in the cups turned a more bluish (less red) according to the amount of vinegar used. This is partially due to the calcium carbonate (CaCO3) which makes up the eggshell, because it is a base.

Step 3: The Results

In the first picture, the eggs were removed from the dye, the ones in vinegar turned a robin egg blue. Were the one with baking soda and the control took on almost no color change.

The more vinegar, the darker the color. However, too much vinegar can cause spots on the eggs where the vinegar dissolved the calcium carbonate and formed CO2 gas.

In the second picture, the eggs were finished off with a light coating of olive oil on a paper towel. This gives the eggs a nice sheen and helps preserve the eggs.

Step 4: Other Colors of Eggs

Some other colors you can get:

Pink - avocados, beets
Blue - red cabbage, blueberries, grape juice
Yellow - turmeric, carrot tops, dandelion flowers, yellow onion (not skins), goldenrod flowers.
Orange - turmeric
Red - yellow onion skins
Green - red cabbage and turmeric, red cabbage with little vinegar, spinach (without vinegar)
Brown - fiddlehead (fern), leaves, acorns, hickory nuts, coffee, tea, ...
Gray - black cherry juice

Step 5: Other Videos

Blue - red cabbage,
Dark Blue/Purple - Blueberries
Yellow - turmeric, carrot tops
Red - yellow onion skins
Gray - black cherry juice

Step 6: Thank-you

If this was interesting, I have more instructables coming and a growing playlist of dying eggs with other natural dyes. Also, look for upcoming naturally dyed t-shirts.