Broken microwave glass can be dangerous for any number of reasons. Broken glass can lead to cuts, to escaping gas and to an inefficient microwave. Unrepaired glass will also lead to more breaks, as the stress of heating and cooling will cause cracks. Fortunately, it is relatively easy to glue broken microwave glass back together.
Spread the newspaper over your working area. If you are able to remove the microwave glass, find an out of the way spot that is not in direct sunlight. If you must repair the glass on the microwave, spread the newspaper underneath where you are working.
Put your gloves on. Remove glass from microwave if possible and place the pieces on the newspaper. Assemble them approximately how they fit together. Tear off a 2 inch by 2 inch piece of sandpaper and lightly sand the edges where you will be gluing pieces. Wet a piece of newspaper and then lightly dampen one side of each piece that you will be gluing.
Fold an index card in half and then in half again in the other direction so you have something a quarter the size of the original index card. Apply an ample amount of glue to the card, and then use the card to put the glue on all the dry edges. If you are applying the glue to glass on the microwave, use the card to apply the glue over the cracks that need healing.
Press the broken pieces together firmly. Hold them there for 3 minutes. When you have released them, feel free to mop up any errant glue with another index card. Just make sure that you do not break apart the pieces you have just glued together. Let the newly glued pieces sit for 12 hours before you use the microwave again.
If you get any glue on your fingers or skin, wash it off with warm water or rubbing alcohol. To get rid of any bumps of glue, sand them down with sandpaper.
If you swallow or get glue in your eye, immediately contact Poison Control.