If you are about to put that mug in the microwave, you might want to think about it. Here's why:
•A mature clay is stronger and better suited for every day use with food and liquids because it has a water-tight structure.
•The maturity is important because if you microwave a pot that’s not fired to maturity, it gets too hot to touch. That happens because immature clay has small pockets of air left in the clay body, which over time will capture water droplets that heat up in a microwave.
•Clays used for pottery are formulated at different temperatures, and the most common “high fire” clays are “cone 10” and “cone 6.”
So this is a good question to ask a potter as they show you their wares and you consider which one is right for what you need. If the clay is not mature - you're in for a bumpy ride...