Very hot water, especially boiling water, can contribute to cracks in a natural-gourd or wooden mate cup. [Luv Mate’s care guide](https://www.luvmate.shop/blogs/news/ultimate-guide-how-to-cure-wood-or-gourd-mate-cup) warns about pouring hot water into dry wood. The usual brewing temperature is around 70 to 80°C (158 to 176°F), according to [Taragüi’s brewing instructions](https://www.taragui.com/en/post/how-to-prepare-a-good-mate).

Heat doesn’t explain why your first cup leaked during a cold-water soak. That suggests an existing crack, a thin or damaged area, or another defect. Excessive heat, pre-existing damage, or stress as the material absorbed water could explain the other two failures. The timing alone doesn’t tell us which caused them.

A day-long soak wasn’t an obviously unreasonable mistake. Leaving yerba and water in the cup for about 24 hours is a conventional curing method, though the instructions generally call for hot water. Wooden cups may need different preparation, so follow the instructions for the particular wood and maker. [Taragüi’s curing guide](https://www.taragui.com/en/post/how-to-cure-and-clean-mate) describes the process.

For replacement cups:

- Use warm water for the initial wetting and avoid boiling water.
- If the cup is calabash, gently scrape out softened loose pulp without gouging the shell.
- Empty the cup after use and let it dry somewhere with good airflow.

If you used water around 70 to 80°C, I’d suspect the cups’ condition or quality before concluding that you caused all three failures. Curing won’t reliably repair a crack that goes through the cup and leaks.