To do this test you will need a few items.
1. Rubbing Alcohol
2. 2 Mason Jar (lids will need modified, link here)
3. 1/2 cup measure cup
4. Large bowl or tub (white is best)
NOTE: Rubbing alcohol is very flammable so keep it away from your smoker at all times.
First go into your colony and find the queen, set her frame to the side for her protection. Then look for a frame of brood in mixed stages (open and close cells). After the frame is found shake it over your large bowl. Then quickly shake the bees into the corner or edge of bowl and scoop up a 1/2 cup and pour them into the mason jar. Place the lid on the jar before any escape. Dump the remaining bees in the bowl back into the hive and close it up.
A 1/2 cup of bees is approximately 300 bees, which we now have contained in the mason jar. Now pour rubbing alcohol through the screened lid until the bees are all floating, screw on the top jar and shake, shake, shake. The shaking will dislodge the mites from the bees.
After you get your mite count you need to do some math to figure the mite population. For this example lets say I found 12 mites.
12 Mites divided by 300 bees (what we had in jar)= 0.4 x 100 = 4% or 4 mites per hundred bees
http://scientificbeekeeping.com/sick-bees-part-11-mite-monitoring-methods/ scroll down about half way and you will find how to modify it.
Or you can purchase a jar with the modified lid
This population chart shows the growth curve of mite over bees in Aug.- Sept.. A colony with this heavy of a mite load would most likely not survive winter without some kind of a treatment.
Read more about different mite washes here