I use gallon paint I buy new at an auto parts store. I place them
directly on the combs(actually resting on sticks to preserve the bee
space). I've seen colonies take down 5 gallons in less than 3 days. The
syrup(HFCS) isn't in the cans long enough to crystalize, I guess molds
and yeasts wouldn't be a problem. Wash and dry the cans when you're
done. The bees cluster around the cans, and keep the syrup warm.
Important here in the north when October turns cold, and you have
barrels of syrup to feed.