Quick and simple four-spot testing papers for quarter excessive cell counts. An infection causes a change in acidity in the quarter's milk. A couple of drops of milk on the paper from an infected quarter will change the spot colour from yellow to green, or blue/green. Normal quarter milk will not affect the spots. Papers should be kept sealed in the bag until used. All four quarters should be tested simultaneously. This test is particularly useful at the start and end of the season when the RMT test is less reliable. Papers should indicate recovery 3-4 days after treatment.