Food-Grade Lye

• Two types of lye are available for purchase. If you are using lye to make edible foods, only use a "food-grade" product. Food-grade lye has lower levels of impurities, while the lye you buy at a hardware store is likely to contain high levels of heavy metals such as mercury. Food-grade lye isn't something you'll find in the average supermarket; however, you may have to look online or at specialty stores to buy it.

What Is Lye?

• Lye is also known as sodium hydroxide or potassium hydroxide. The chemical is an alkaline, and alkalines are opposite the pH scale from acids. Lye corrodes surfaces it comes into contact with, which is why industrial-strength lye is a drain cleaner and why it will burn your skin.

Using Lye

• When you use food-grade lye to make baked goods, don't use it in its concentrated form. Using a very weak 3 percent solution for baking is common, says Noelle Carter, writing for the "Los Angeles Times." Dissolve 2 tablespoons of lye in 1 quart of water to create a 3 percent solution, or as directed in the recipe you're using. Dip the shaped dough into the solution or use a brush to coat the surface of the pretzel or bagel with the diluted lye. You'll see the dough start to yellow when it comes into contact with the lye solution. The alkali in the lye is neutralized during baking, which makes the pretzel or bagel safe to eat.

Lye Safety

• You need to be very careful when working with lye in the kitchen. If sodium hydroxide comes in contact with your skin, it can cause irritation and burns. Protect your skin from lye by wearing gloves and a heavy apron. Also wear safety goggles to protect your eyes. Lye can irritate your airways, too, so wear a mask when working with it. The chemical will reaction with aluminum, so only use non-reactive bakeware, such as glass or stainless steel, when working with it.