Wierd PH readings...

[Watermom]

I usually wait 3 or 4 hours after adding Borax before retesting.

[bradjo]

Chlorine over 10ppm converts phenol red to chlorphenol red (dichlorophenolsulfonephthalein), Chlorphenol red measures pH from about 5.2 to 6.6 if memory serves turning a dk purple at 6.6 unlike phenol red which is dk purple in the 8's. So you can make a serious error here.

Thiosulfate is base and can give a false high pH reading here's where a 44 ml sample for pH is a good thing.
hth,
Jo