Many types of pies are topped with billowing meringues that give them a beautiful finished look and a lovely contrast between a denser filling and a lighter topping. But even though the meringues look good when you spoon them on top of a pie, they often start to weep and make your pie look less than perfect. Weeping is when a meringue releases droplets of liquid, giving the meringue the appearance of having tears or raindrops all over it – hence the name. Weeping is caused by an unstable meringue, one that is undercooked or that it simply has too much moisture in it.
Many pies are topped with a meringue made by beating sugar and egg whites together, spreading it onto a hot pie and baking it for a few minutes in the oven to brown it. This method generally sets the outside of the meringue and counts on the heat from the pie to help set it from below. Unfortunately, a few minutes in the oven isn’t really enough time to fully stabilize a meringue and meringues made in this way will often shrink, separate from the crust and start to weep after a short while.
There are a couple of solutions to the problem. One option is to extend the baking time slightly for your pies, giving the meringue more time to cook through. Another options is to add a stabilizer – such as cornstarch – to your meringue to help to absorb excess liquid. A tablespoon or so should be enough to help control the weeping initially, and it is easy to incorporate into a meringue. The stabilizer will help your meringue to last longer than one with nothing added, but once the pie is in a humid environment, such as the refrigerator (or your kitchen, if you live somewhere it is very humid), it may begin to weep anyway.
The most reliable way to prevent weeping is to replace a simple meringue with a very stable Italian Meringue. Italian meringue is made by beating egg whites until they reach soft, fluffy peaks, then slowly streaming in boiling sugar and beating the mixture until it is thick and glossy. The resulting meringue is fully cooked so it is very stable and it is significantly less likely to weep than an uncooked meringue (typically only in very humid conditions), and you can spread it on top of a pie and bake it until it browns in the oven without worrying about having an under-cooked meringue on your dessert.