Oh yes, sugar and fondant. When I left I was about to answer a question that had come in, specifically: if sugar turns opaque as it cools, then how are clear hard candies made?
Ah yes, very interesting question. For the answer it helps to look at a chart that shows the various phases that sugar passes through as it “cooks” into caramel, say here. Notice that the temperature for hard candy is about 310, right up at the very top of the scale, just before the sugar starts turning into caramel. This is the point where so much of the water has been boiled out of the syrup, it’s about 99% sucrose…basically molten sugar. If you suddenly cool the sugar, the loose sucrose molecules won’t have anywhere to go. They’ll be trapped in a mass without a syrupy medium to move around in. Unable to form crystals, they’ll freeze in a jumble of individual molecules through which light rays will pass easily. The result is basically a hard candy glass.
The next question logical question is: if that’s true, that hard crack candy has so little moisture in it that it freezes instantly when it cools, why is caramel soft and gooey even though it’s cooked to an even higher temperature? Part of the reason is that fats like butter and cream get added to it once it’s nice and brown. However another big part of the reason is that as sugar turns to caramel, as it burns essentially, the sucrose molecules basically break apart. They separate into all sorts of odd pieces, some of which stay small, others of which recombine to form a wide array of odd and interesting (and flavorful) molecules. So where you once had a virtually homogenous mixture of one type of molecule, you suddenly have scores, even hundreds. They lack of uniformity means they don’t form crystals very well, which means the mixture flows.