Typical lazy guy problem - I didn't clean my ceramic cup after using it and haven't used the cup in about 3 weeks. It's been sitting on a shelf in my office. I noticed today it had some little mold bumps at the bottom (must've just been a thin film of coffee left over).

I took it down to our kitchen at work and scrubbed it with soap and water and a sponge. Is it safe to drink out of it?

I read around and many say it's safe, many say unsafe. There were many suggestions to just bleach the cup. That seems like bit much to me.

Is soap and water strong enough? I washed 3 times.


2 Answers 2


I would feel confident drinking out of a ceramic mug after a good scrubbing with soap and water. Smooth (glazed) ceramic surfaces are more easily cleaned than rough ones, so perhaps the rough ones deserves extra effort.

If there is a concern about sanitizing the mug, putting water in the mug and leaving it in the microwave on high until the water boils should kill any mold. According to this 2012 Penn State Extension bulletin on important temperatures for food safety:

Processing foods in a boiling water bath will kill most bacteria, molds and yeasts.

  • 1
    Anytime you boil water in the microwave, make sure you give it a good stir before you turn on the power. A microwave can superheat still water. Superheated water can "explode" out of the container when disturbed. see animations.physics.unsw.edu.au/jw/superheating.htm
    – B540Glenn
    May 30, 2017 at 13:42
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    If the mug isn’t microwave safe, boiling water from the kettle and some resting time will work as well. Perhaps repeated once or twice. Hot enough for a prolonged time is what you aim for.
    – Stephie
    Jul 8, 2021 at 14:57

I suggest using a small amount of bleach. Servings would be around 1 teaspoon to a gallon of water - of course, you can make this mix smaller. If you can smell the bleach, you're most likely using too much; you also have to air dry the thing you use this trick on. This also works with lunch boxes and pots. Feel free to try it out!😁 P.S This has worked for me before.

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