Are the mugs totally black when cold?
Not totally. A faint smoky image can be made out when cold.

At what temperature does the design start to light up?
About 104 degrees Fahrenheit. Just add boiling water to make a cup of tea, and the design is revealed within a few seconds as the mug heats up. It fades to black as you finish your drink and the mug cools down again.

Does anything else happen when you add hot water?
People tend to go 'Wow' when they see them for the first time. Sometimes they pour the water back out and in so they can see the colors change again.

Are they poisonous?
No, of course not. Our mugs are totally safe to drink from.

Will they last?
Yes. The mugs are as durable as any high quality household mug. Barring dropping them on the floor, they will last for years.

Can we put them in the dishwasher?
The dishwasher is not recommended. Nothing dramatic happens, but they gradually start to fade.

What about the microwave?
The microwave is fine.

How do they work?
The design is printed under a special black thermochromic coating. This coating becomes transparent when heated, revealing the design beneath. Because both the coating is black and the design background is black, it gives the impression that the design is appearing, rather than the coating disappearing.