coffee exploded

[trapper]

Yesterday getting ready to visit kids I heated coffee in microwave in FF cup.  Went over to sink to pour it into a travel mug  As I started to pour the coffee either boiled over or something causes it to explode.  Soninlaw thinks it may have been caused by an air bubble in the coffee,  My thought is that the coffee was near boiling and as the container in a microwave gets hoter than the contents pouring may have caused the coffee to boil over. any other ideas?  Minor burn on my hand but worse my FF cup is cracked and a couple chips from inside making it useless.  Have to see if Jeff has more to sell.

[TimRB]

Possibly the coffee was superheated.

http://en.wikipedia.org/wiki/Superheating

Tim

[clww]

I heat mine in my FF mug every morning, then pour it into the travel mug, too. I've never had this happen, and I hope it doesn't.
Sorry about your hand and the mug.

[Chuck White]

Could have possibly been a piece of metal in the ceramic mixture that the mug was made of!

[Jeff]

The problem is super heating. Check out the link given on the section about microwaving.

[Ianab]

Superheating is the cause. The water in the centre of the cup can actually get OVER boiling point, but it wont boil as it's not in contact with any solid surface for the bubbles to form. When you disturb it, often by adding coffee, it instantly starts to boil furiously, and spills out over your hand. 

It's a bit like opening an overheated radiator. In that case the pressure is keeping the water from actually boiling, release the pressure, the boiling point comes back to normal, and you instantly have a geyser. Not exactly the same mechanism, but the result is similar. Hot water all over your hand.  :-\

[DDDfarmer]

Cooking some corn on the cob in the microwave one day and doing the second round of corn when the measuring cup of water exploded.  Ruined a good measuring cup but the microwave was ok.  I never re-use the same water now.