Although the only ingredients are egg whites and sugar, the sometimes tedious process of making meringue can be made easier if a few simple rules are kept in mind. Before starting to make the mixture, it is important to ensure that the utensils being used, as well as the egg whites themselves, are very clean and free from excess grease and fat, including any yolk left in the whites. The meringue will be easier to make if the ingredients are all room temperature before whipping. The type of sugar used can make a large difference, with granular sugar sometimes being the cause of excess moisture that can coalesce on the surface of the whipped egg whites. Humid weather, an overheated oven and eggs that might have been over-whipped are all additional factors that can ruin an otherwise well-made meringue.
The process of making meringue involves developing a structure inside the egg whites that holds increasingly smaller pockets of air as the whites are whipped. Sugar will bond with the proteins holding the air and help make the structure very durable and resilient, as will the addition of acids or the use of a reactive copper bowl. The two elements that will stop a light, smooth meringue from forming are moisture and fat. Fat will prevent the proteins from creating a strong structure to hold air, and moisture can degrade the bonds or remove the air from the egg whites.
To ensure that no excess oils or fats are incorporated into meringue, the bowl that will be used for whipping should be made from a material that does not hold grease and should be cleaned before use with an acidic substance such as lemon juice to completely remove any residue. Additionally, hands and fingers should not touch the inside of the bowl or any other cleaned utensils that will be used to whip the egg whites, because oils on the skin also can transfer and cause problems. When the egg yolks are separated from the whites, no yolk at all should be present in the whites when they are used. The same care should be taken to ensure that the mixing bowl and all utensils are very dry to avoid adding unwanted moisture to the mixture.
When starting to whip meringue, the protein structure that forms inside should be allowed to develop slowly at first, because whipping too aggressively in the beginning will create a fragile structure that will collapse quickly. After the whites have been whipped into a soft froth, only then should superfine sugar be added. Adding sugar that has grains that are too large, or adding it too early, can affect the final texture of the mixture and potentially act like a magnet, attracting moisture in the air.
Depending on the circumstances and the final use for the meringue, a stabilizing acidic ingredient such as vinegar, cream of tartar or lemon juice can be added in small amounts to re-enforce the protein structure holding the air. If the whipped egg whites are going to be baked, then careful attention needs to be paid to them while baking, without opening the oven door, to ensure that the whites are not cracking, browning too quickly or shrinking too fast from overly high heat. If at all possible, the final tip for achieving the best results is to only attempt to make the mixture when there is low humidity outdoors and the weather is dry.