A good question came in today about caramel making. Specifically: why add water to the sugar at the outset of the caramel making process when you’re just going to evaporate it all out anyway? The reason is to protect the sugar from heating up too fast and burning. True, that’s what we want to get to eventually, but it’s far better for the whole thing warm up and “burn” uniformly than for some of it to cook to brownness while much of it is still “in the raw” so to speak.
One of the things that I find so interesting about cooking sugar syrups is that their temperatures are really a measure of their moisture content. In fact the entire practice of candy making is based on this idea. A “hard crack” candy syrup isn’t harder than a “soft crack” syrup because the sugar is “cooked” longer (remember that sugar molecules in a syrup don’t change unless they’re broken by caramelization), it’s because it contains less water. Temperature is the measure of exactly how much water remains.
The reverse side of this notion is that the temperature of a sugar syrup can’t go up until the right amount of moisture leaves. This is why it can take so long for a candy syrup to heat even over a high flame. Until enough steam escapes, that syrup won’t get one degree hotter. This is another reason caramel-making is better in a skillet, since a skillet provides more surface area and faster evaporation.