Egg Whites Won't Stiffen I was making Waffles the other day, and was whipping egg whites in a plastic Tupperware, but after an extremely long time, they hadn't stiffened. I looked in the special help section of my cookbook to find out why and I noticed that it says that egg whites can be beaten in glass or metal, but not plastic.

Does anyone know why this happens?
It is virtually impossible to get every last trace of grease/oil out of plastic containers.

Egg whites will not whip with even the slightest trace of oil/grease anywhere in the bowl, on the beaters, etc.

Ergo, plastic and whipped egg whites do not go together.