If you have kids – or even if you don’t – you’ve probably used an Easter egg dyeing kit a few times. But have you ever wondered why you have to add the vinegar to the dyeing solution? Today we’re talking about the science behind dyeing Easter eggs and a fun experiment you can do at home with your kids.
Science behind the coloring of Easter eggs:
- Adding vinegar to water makes it more acidic
- A pH of 4 - about a teaspoon of vinegar per half-cup of water - consistently yields a smooth, pretty color
Egg shells are porous – and the acidity breaks down the shell of the egg ever so slightly, so that the colored liquid can permeate the shell – essentially allowing the vinegar to go through the shell, carrying the color with it.
If it’s too alkaline (a higher pH), the eggs won’t dye as well; the color won’t penetrate the shell.
If it’s too acidic (a lower pH), the acid dissolves the eggshell too much, and reacts with calcium in shell to produce bubbling that it will leave blank spots on the surface of the egg where the dye wasn't able to attach.
Source: Darryl Holliday, assistant professor of food science at The University of Holy Cross
What you’ll need:
- 5 hard-boiled eggs
- White vinegar
- Lemon juice
- Cream of tartar
- La Croix sparkling water (any flavor) – tested at pH of 3.68
- Measuring cups and spoons
- Mixing spoon
- Cups for dyeing solution
- pH test strips (optional; available at drug stores)
Prepare the 5 egg dye solutions using the following measurements:
- Vinegar: 2 teaspoons vinegar + 1 cup water
- Lemon juice: 2 teaspoons lemon juice + 1 cup water
- Cream of tarter: 1/4 teaspoon cream of tartar + 1 cup water (room temp water; stir well to dissolve)
- Water-only: 1 cup water with nothing added acid a
- La Croix: 1 cup La Croix Sparkling Water
Test the pH of each solution with pH strips.
Add Easter egg kit dye tablet or 10 drops natural food coloring to each solution and stir. Place one egg in each solution and allow to sit for 10 minutes. Remove eggs from solution and observe the color saturation produced.
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