I have been out of BeeKeeping for 10 years and am wondering, what are propolis collectors and what is a good design for one. I looked in my old library and could find nothing on them. I assume that they are a device inserted into the hive that the bees are inclined to fill with propolis?. How is the propolis harvested, if it is indeed soluable in alcohol then it would be convenient if it was a device small enough to submerge in a tub of alcohol otherwise it would be a tedious job.