Why a mortar and pestle, and not a grinder

Electric grinders heat the herb. The mortar does not. For botanicals where the oils matter, the heat is the loss.

We grind herbs in a stone mortar at the bench rather than in an electric grinder. The reason is heat. Electric grinders generate friction, friction generates heat, and heat drives off the volatile aromatic oils that make botanical herbs interesting in the first place.

The stone mortar is slow, hand-powered, and produces uneven particle sizes which sounds like a flaw but is actually a feature. Brewing extracts at different rates from different particle sizes, so uneven grind produces a more complex cup than uniform powder.

We use a 6 inch granite mortar, weighty enough that it does not slide on the bench. The pestle is unfinished hardwood. The whole thing cost forty dollars in 2019 and has paid for itself by orders of magnitude in product quality. If you are starting a tea house, this is the first tool to buy and the last tool to upgrade.