Lye-heavy soap can be harsh and drying to the skin. If you suspect that your soap is lye heavy, or are just curious about the pH levels, you can easily test your soap. Here are two ways to test the pH of your soap:
1.) The Zap Test: Take your bar of soap and touch the tip of your tongue to the edge of the soap. If you experience a slight zap feeling (similar to licking a battery), then your soap is probably lye heavy. If you don't want to lick your soap (and I can understand why you wouldn't want to) you can use pH testing strips.
2.) Using pH strips: Take your bar of soap and slice off a sliver. Run it under some water and rub it to create a lather. Dip the end of the pH testing strip into the lather and make sure the strip gets fully saturated. The other end of the strip will turn a color and match that color with a color on the pH guide. A normal bar of soap should be between 8-10 on the pH scale.
Is your soap lye heavy? Don't throw it away just yet, you can easily turn your lye-heavy soap into laundry soap! Here is a Soap Queen blog post where Anne-Marie explains how to easily turn lye-heavy soap into laundry soap.