Egg whites should be firm but not dry when beaten. Your egg whites should keep their shape while still having a glossy sheen to them. If they are dry, the shells will crack. Avoid a high-powered mixer while beating the egg whites. Instead, during the first three minutes, keep the volume on medium. Also, do not add the sugar too gently during the first two minutes. Then, for the rest of the time, beat on medium-high. Macarons Phoenix