Typical lazy guy problem - I didn't clean my 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
    A planet full of students is proof that coffee mould doesn't kill ;-) The kitchen sponge is apparently the most dirty thing in your house/office. I think bleach residue will do you more harm. A little bit of penicillin will not harm ;-) – TungstenX Oct 2 '15 at 18:06
  • What kind of mug is it? – hardmath Oct 3 '15 at 20:48
  • Question - how tough are you? – Caffeinated Oct 4 '15 at 16:19
  • @hardmath ceramic – Jaken Herman Oct 6 '15 at 18:55

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.

  • 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 '17 at 13:42

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