They are thicker than beaten whole eggs, and can stand for 5 - 8 minutes before starting to deflate.
Sugar stabilizes egg yolks much the same way it does with beaten egg whites.
Superfine sugar is recommended because it dissolves easily and makes a better cake or one with a very fine texture. When working with sugar and yolks, mix them together quickly and evenly. When the yolks come in contact with the sugar, a chemical reaction occurs, heat is produced and the eggs begin to scramble. They will cause lumps in the final product. Separate yolks from whites , and place them in separate bowls.