Based on some odd stuff going on in our pool with CYA tests... both those done by my wife and those at a pool store. I got interested in how to check the CYA test accuracy. From reading here I think I understand that we should take the reading when the black dot is gone, looking at the tube in daylight (but not direct sunlight) and holding the tube at waist level, or about 3/4 arm-length away.
My wife had been peering into the tube as close as possible to make absolutely sure she could not see any indication of the dot. So... now we both tried it looking at waist level. OK... a little different. But still after each drop if you study the tube you can find the edges, an outline of the dot and it takes quite a bit more drops from the point the dot becomes not readily visible but faintly recognizable, to the point where the dot is "gone" no dot, no way, no how...
I did some googling and even watched a video. They all say "can't see the dot"... but are not so clear. The video panned over the tube and the guy said "I can't see the dot", but the video barely let you see the tube, let alone give any idea if the dot was really gone or just very faint.
Any helpful descriptions to offer?