How long till paper catches on fire in microwave?

Question

How long would it take for a sheet of paper to catch on in an average microwave? Also, how long would it take for an average label, or sticker?

Answer 1

Food can be cooked on paper in a microwave because the waves go through the paper.
A microwave works by causing the molecules in the food(primarily water) to vibrate faster and the definition for temperature is how fast the molecules are vibrating.

If just paper is put in a microwave the micowave will spark due to the waves reflecting back at the magnetron and can cause damage.
A label on a glass beaker should not be a problem if the beaker has liquid in it.