[Chemistry4me (OP)]

I was just making some macaroni & cheese in the microwave, and I had to pause the microwave half way through for about 2 minutes to go do something. When I came back and resumed the cooking, I found that the viewing window was all fogged up with condensation. So I opened the microwave, wiped the viewing window clear and then resumed the cooking, after that, the window did not have condensation (at least, not nearly as much as before) on it, even when the sauce was bubbling away. Why is this? Is it because when the microwave is on, it can remove the air inside and when it stops it cannot?  []

[lyner]

Was it not just because the window had warmed up for the second half of your observation?

[Don_1]

While the microwave oven is on, the water in th food evaporates and remains evaporated, but as soon as the microwave is turned off, the evaporated water can condense.

[Chemistry4me (OP)]

Hmm... I do like the sound of Don_1's suggestion, but whether it is correct...

[Madidus_Scientia]

I reckon you answered your own question, when the microwave is going there's an exhaust fan, but while it was stopped the steam condensed onto the glass.

[Chemistry4me (OP)]

Really? You think so eh?
I suppose it could depend on the quality of one's microwave. But still, I like Don_1's idea.