Put Away The Soap. Here's How You Should Clean Your Molcajete
A molcajete is a Latin American-style pestle and mortar that dates back to the Aztecs and is still widely used today. It's traditionally made from porous volcanic rock and stands on three legs. It's more rustic than its granite or marble counterparts and, as such, needs to be cared for differently. Like with cast iron vessels, soap should not be used on a molcajete due to its porous nature.
Molcajetes are like cast iron in other ways, too. They develop seasoning over time and should be prepared with rice or rock salt before they are first used. Used with the heavy tejolote (pestle), this material smooths out the rough edges and keeps that grit from joining any food you may grind later. Just as the molcajete absorbs the flavors of whatever food is processed inside its bowl, it will also absorb the flavor and aroma of soap.
The taste of the soap can then transfer to whatever food is made in the molcajete. To avoid this use only warm water and a brush to clean it. Then allow it to air dry completely before storing or else mold could develop on its surface. If the molcajete develops a foul odor, simply grind white rice or rock salt inside to scrub out the smell.
How a molcajete works
A molcajete works because the weight of the tejolote does well at grinding food like peppers, avocados, and spices into a fine powder against the rough stone surface of the mortar. Pressing and twisting the tejolote against the mortar releases the essential oils out of what is being ground. These flavors and aromas seep into the pores, which develops the seasoning that is unique to this style of mortar.
There are many advantages of a molcajete, like being in close control of the grinding process, which then determines the consistency of the food and its seasoning. It's also easier to extract all the flavors from whatever you're processing. Those flavors then soak into the pores of the molcajete and are released when it is used again.
Grinding spices is a popular use for a molcajete. It's also often used to make salsa, guacamole, and pesto and can be used as a serving dish or warmer, as it retains heat well. No matter how the molcajete is used, forget about the soap when it's time to clean it, and just stick with warm water.