Place the perforated cup inside the solid cup.
Fill the cups 2-3/4" full of either Dawn Ultra dishwashing detergent (1 Tbs to 1/2 gallon of water) or 90% rubbing alcohol.
Take a sample of a level 1/2 cup of bees from a frame adjacent to, but not containing brood (avoiding drones) and dump it into the sampling cups.
Immediately put the lid on the cup.
Let the bee sample sit for 1 minute to allow for the mites to release from the bees.
Then gently swirl the cups for at least 30 seconds to allow the mites to precipitate through the bees. Swirl to resonate with the wave, just enough
so that the bees at the bottom are gently tumbling.
Remove the lid, and lift the perforated cup out and dump the bees.
Count the mites that have settled on the bottom of the solid cup (easiest to view looking down on a 6" 10x magnifying mirror placed 4" below the cup).
We suggest taking action if the mite count is over 1 in the springtime, 6 during the summer, and zeroing the infestation by the autumn equinox to allow rearing mite-free brood to form the winter cluster.
References:
An Improved, but Not Yet Perfect, Varroa Mite Washer
Refining the Mite Wash : Part 4 Comparing the Release Agents