Gourds used in making mate cups are a natural product and contain dried pulp. The curing process helps clean the gourd--and inhibit mold growth. To cure your gourd:

• Rinse it with plain warm water and remove any loose pieces of the dried gourd with a spoon. Do not remove the inner hard "stem" from the flower end of the interior of the gourd or this could result in a greater likelihood of leaking.
• Drain.
• Add fresh or spent yerba tea with more warm water and let sit for an entire day.
• Repeat these steps again, drain the yerba fluid, let dry completely, it helps to put a paper towel to help absorb the moisture.
• Your cup should be ready to go after one day of curing, yet some can go for two or three consecutive days.
• Your gourd then will be infused with flavor and ready to use.