Pretzels baked without salt can be frozen for up to 1 month. Spray the frozen pretzels with water and sprinkle with salt before reheating in a 275° oven until warmed through, about 20 minutes.
Food-grade lye can be ordered from essentialdepot.com. Coarse salt and pretzel salt can be found at specialty-food stores or online at americanspice.com.
Lye Alternative: To make a lye alternative, dissolve 1/2 cup baking soda in 2 quarts of boiling water. Boil the pretzels for 30 seconds, then drain on wire racks before salting and baking.