What makes pretzels brown in the manufacturing process?

Pretzels are dipped in a water/base solution. You can use baking powder but it does not work nearly as well as the real deal which is sodium hydroxide. If purchasing sodium hydroxide I would ensure to get food grade and only use what a recipe calls for. Natrumlauge is the German Word for sodium hydroxide. You can dip rolls into it and make pretzel rolls or laugebrotchen as they are called in German. Cheers!