When separating eggs, it’s important that none of the yolks mix with the whites. Yolks contain fat, and even a tiny amount of fat will ruin an egg white’s ability to trap and hold air.
Eggs separate best when they’re cold, right out of the refrigerator.
Before you begin, set three bowls or containers on the counter in front of you. Crack an egg and separate the white into one bowl, put the yolk in the second bowl, and then pour the cleanly separated white into the third. Repeat with each egg. That way, if a yolk breaks or an egg is spoiled, you won’t contaminate the entire batch of whites.
If you spot a small speck of yolk in the whites, use a clean egg shell to scoop it out; it will attract the yolk like a magnet.