Drying agent or cold weather food?
If we have a moisture issue, and the nature of thermodynamics (warm moist comming into contact with cold dry) is going to create 'fog', then regardless of the drying agent we use (sans harmfull) is irrelevant, we could be using sawdust or sodium silicate (in little tiny removable packets).
If we are trying to supplement the hive with a product that the bees could actually utilize (sucrose) and not frozen (dry) that also acts as a drying agent - what can it hurt? Bees are going to find a way to process it. They're not foraging for the non-existant, and they have to stay close anyway to help the cluster survive the cold.
But questions remain... Does the presence of sugar draw bees away from the cluster, regardless of their need? I notice clusters of 25-50 bees on the dry sugar feeding, when I am quite sure they have plenty of stores of honey below them. A number of them end up getting frozen on the sugar mound.
Does the presence of feed contribute to their desire to store, binding brood comb, and creating a expansion limit for the queen in early spring?
What do we do with the leftover layer(s) of sugar late winter/early spring?