the heat goes into the work of evaporating
water molecules from the syrup, and less into
actually raising the temperature of the syrup;
so the syrup temperature rises only gradually.
But as the sugar concentration passes 80%,
there’s so little water left that both the
temperature of the syrup and its boiling point
rise more rapidly. As the concentration
approaches 100%, the temperature rises very
fast, and can easily overshoot the desired
range and brown or scorch the sugar. To avoid
this, the cook should reduce the heat toward
the end of cooking and keep a careful eye on
the syrup temperature.
Setting the Sugar Structure: Cooling and Crystallization
The final texture of a candy is determined by
the way in which the sugar molecules in the
cooked syrup cool and settle into a solid
structure. If the sugar forms a few large
crystals, then the candy texture will be coarse