Testing alkalinity - question

[binovc]

Using the TFT100, after adding 5 drops of R-008 to turn the sample to green, I'm not sure when to stop adding drops of R-009 to turn sample back to red.
At 4 drops, the sample begins to turn red, but it is not until 6 drops that it is more definitely red.
So would my alkalinity be 40 or 60?
Thank you.

 

[jblizzle]

In all tests, add drops until the last drop causes no further color change and do not count the last drop.
So you are likely at 60 or 70ppm.

 

[mknauss]

Pool School - Total Alkalinity

Counting the number of drops as you go, add R-0009 one drop at a time, swirling to mix after each drop.
Continue adding drops until the color changes to something more or less red, pink, yellow, or clear. The sample may switch between green, blue, and gray while you are adding drops. That is not the color change you are waiting for.
Continue adding drops as long as the color continues changing. The final drop, that does not change the color any further, does not count.

 

[binovc]

Thank you!