Caring For Your Porcelain Cup
Daniel Jessep's cups are made from vitrified porcelain, which means as far as pottery cups go they don't get much stronger... but obviously not unbreakable! Vitrified means turned into glass, and essentially in the firing to +1200°C, the clay does come out as strong as, or even stronger, than glass. You can tell a vitrified cup by holding the bottom of the cup in one hand and lightly flicking the rim of a cup with your fingernail. You should get a satisfying "ping".
Washing
The porcelain cups and silicone lids are dishwasher safe but please still handle with care. Treat them like you would your favourite cup ;-)
Heating
Porcelain, like glass, is prone to thermal shock which means the cups don't like going from one extreme temperature to another. E.g. Freezing cold to boiling hot. Pouring boiling water into the cup at room temperature is obviously fine, but not pulling a cup out of the freezer and pouring boiling water into it.
The silicone lids can handle a temperature range between -40°C to 230°C.