Traditionally, pretzels are made using a lye bath. I used baking soda in this recipe because it is a more common household ingredient. Lye is Sodium Hydroxide which is caustic and needs to be handled carefully. I use lye when making soap. Lye has a pH of 13 whereas baking soda has a pH of 8. Lye will give the pretzels a darker, chewier texture which is why professional bakers use it. For the home cook or those baking with children, it is perfectly acceptable to use baking soda.