Three methods exist for incorporating sugar into the egg foam: French, Swiss, and Italian. The least stable of the meringues but most popular and easiest to make is the common or French meringue. Here, sugar is whipped into room-temperature egg whites, at about 70°F (21°C), without the use of heat. To make Swiss meringue, the whites and sugar are first whipped with a balloon whisk in a bowl set over a hot-water bath (bain-marie) and warmed to 110° to 120°F (40° to 50°C) to dissolve the sugar; the mixture is then beaten until cool on medium-high speed in a stand mixer. Italian meringue, the strongest of the three, starts with egg whites at room temperature. After whipping the whites to soft peaks, a hot sugar syrup is added and the mixture is beaten until cool. All three meringues should contain cream of tartar or lemon juice for stability and added volume, and should be whipped until thick, smooth, and glossy.