To avoid bitterness, a cuia (Gourd) is usually Cured or "broken in" before using.  For pure yerba mate (with no additives like sugar), fill the gourd with fresh yerba mate and add boiling water. Let stand for a day. Rinse the gourd and repeat for two or three days.  

For "sweet" mate, wet the gourd with boiling water, add two or three teaspoons of sugar and a small piece of burning coal. Cover the gourd mouth and shake vigorously to burn (caramelize) the sugar on the sides of the gourd. Empty the gourd and proceed as instructed above.

Gourds are divided in two categories: curable and incurable. Incurable mates are those made of non-porous materials (glass, metal, china, etc.). Incurable mates lose all "memory" of the taste when they are washed. For best flavor a curable Gourd should be used. 

 Cleaning the Gourds: The gourd should be hand washed only using hot or boiling water and NO soap or detergent. Do not put the gourd in the dishwasher. Keep the gourd dry between uses, placing a paper towel or napkin in the gourd after use will help absorb excess moisture.