An early morning visit here on an early frosty spring morning is a must and you will see a hive of activity including helicopters, frost pots, windmills and overhead irrigation sprinklers all being put to use to protect the small buds on the vines from the damaging frost.
One of the more interesting methods is to run giant sprinklers through the night, causing water on the vines to freeze over the tender growth. This works because, when water reaches its freezing point it releases latent heat. It can be difficult to understand how ice formation gives off heat. (A chemist would describe ice formation as an exothermic process, one that gives off heat.) It is easier to grasp, however, if you first think about what happens when water reaches its melting point. In order for water to make the transition from solid to liquid — in other words, in order to melt ice — energy must be added to the ice. (A chemist would describe this as an endothermic process, one that requires heat.) This energy comes in the form of heat. Once the ice has reached its melting point, the resulting water contains that energy. Now, in order to reverse the phase transition — in other words, to freeze water — the water must give up that energy. The amount of heat generated is small, but enough to get trapped between the green tissue and the ice and keep the vines protected as long as it doesn’t get too cold or stay cold for too long.
The cache can be found at the following coordinates
S 39 312.46 0.95 594.22
E 176 2430 53.53 1629
