The stages of beaten egg whites are foamy, soft peak, firm peak and over beaten, according to About.com. Room temperature whites beat more effectively than cold whites, and the entire yolk must be removed for successful beating.
At the foamy stage of beating, the whites are mostly still in liquid form, possibly with some bubbles on the surface. At the soft-peak stage, the mixture is fully white, and it holds its shape in the bowl. The whites are at the soft-peak stage when the beaters are lifted and the mixture forms a soft peak. The firm-peak stage is achieved when the beaters are lifted and the whites form a firm peak. Egg whites that are beaten past this stage become over beaten and are not recommended for use in recipes, according to About.com.