I have been following with great interest the threads about testing CYA. I have been "vigorously" shaking my CYA test as opposed to "tilting" back and forth to mix. I used my usual method which was vigorously shaking and hit my target of 70 ppm of CYA. I then immediately repeated the test with a tilting back and forth to mix and tested at 60 ppm. I poured back and forth to test each method a total of three times and each time achieved the same test results of 70 and 60 respectively (no difference in a pour back and recheck). I know there has been considerable discussion of the accuracy of this test, and thought I would add my experience and see what others thought.
Here is my full set of numbers
CYA 70 ( with vigorous shaking) 60 ( with tilting back and oath)