Don Felipe personally walks his fields and selects agave plants for their maturity and quality. The harvested agave is slowly steamed in brick ovens and crushed with a stone wheel. It is then fermented in wood tanks and distilled to exactly 80 proof so that water is never added to dilute the tequila. El Tesoro is aged in American oak bourbon barrels which are placed in Don Felipe's humidity controlled cellars. There they sleep, the flavor and color developing naturally with time, until he selects them from blending and bottling.