"Illusion is the first of all pleasures."

This post we're going to continue with our science lesson and debunk a myth about a common type of paint.

If I were to ask Laura*, the little four year old that I babysit on occasion what she thought of egg tempera paint she would most likely shake her head and laugh, before giving us her opinion on the matter:

"No silly! Then everything would be yellow!"

It's true. Many people stray away from egg tempera paint for various reasons; but most of the time because they assume that the egg yolk, being yellow, will cause the paint to take on a yellowish hue, no matter the color. This is an urban legend and actually the paint that takes on a yellowish hue when dry is not egg tempera, but the alternative that many turn to in order to avoid it; oil paint. In order to understand this we must take a closer look at the chemistry of eggs for a moment.

An emulsion is a suspension of liquid within another and a characteristic of them is to display more color when wet then dry. This means that the ‘yellow’ of the yolk is bright when wet and will disappear through the paint making process as it dries. Any remaining ‘yellow’, will then be bleached out by the light. Once the substance is clear and to the right consistency, it can then be mixed with a pigment to create the desired shade. Oil paint, however, tends to yellow with age, and unless the proper amount of oil is used on each layer of the painting, it has a very good chance of cracking and splitting. One advantage to oil paint is that it can be stored and used over a period of time while egg tempera must be made before each painting session.

That's all for now folks, hopefully you understood my little chemical babble. If you'd like to learn more about egg tempera paint, check out:

http://www.paintmaking.com/eggs.htm

*name has been changed