Egg Engraving

    Kids, let's use some chemistry to engrave your name on a hard boiled egg. It's actually a process of reverse-engraving, because we'll make all of the shell disappear EXCEPT for your name

    Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

    First, your adult partner will have to hard boil some eggs for you (only one is needed for the experiment, but you can always eat the extras). With a china marking pencil or a wax crayon, print your initials or your first name, large and fairly thick, on the shell of a hard boiled egg. Now put the egg in a glass large enough to hold it and add enough fresh white vinegar to cover it. Tiny bubbles should form on the egg which show that the acid in the vinegar is reacting with the shell. The shell under the waxy letters is protected from this acid action. In an hour or two, when the bubbling stops, replace the now neutralized vinegar with a fresh supply. After another two hours wash off the egg under running water. Rub your fingers over the letters and they should stand out in relief.

    You can even try to GENTLY remove the wax coating with a soft brush and scouring powder under running water. An average eggshell is .094 inches thick. It's made of 3.5% protein, 1.5% water, and 95% calcium carbonate mineral. It is this CaCO3 mineral that reacts with the acetic acid in vinegar. If half of the shell has dissolved during the four hours, then it has only about an .05 inch-thickness left. So Be Careful!

    If you are interested, the very first ChemShorts column (published way back in January 1992) was called "The Naked Egg" and tells you how to completely dissolve an eggshell. Click here to see this ChemShort


    Kathleen Carrado Gregar, PhD, Argonne National Labs 
    [email protected]
    November 1999


    Reference: "Mr. Wizard's Supermarket Science" by Don Herbert, Random House: NY, 1980, page 41.