Help reading pH chart

[jiffy]

I wanted to test my pH today, and noticed something. On the freshwter pH color card, it reads about 7.5 - 7.6 I also tried the freshwater high pH range color card and on there it said almost 8.0

 

[thecichlidaddict]

Did you do a second test to make sure you get the same readings?

 

[susangc]

The other question is -- did you read the results at the right time? My master kits specifies a reading at 30 seconds after the dip. Waiting longer might skew the test.

Susan

 

[Tenko]

You'll also find that taking chart readings at different times of the day may affect the results due to lighting conditions. I prefer using natural light to use the chart, if I do a test the same day but under room light only I get quite a large difference.

A large difference is also made by one room with rather unpleasant pink walls. It's seems a bit stupid that walking from one room to the other gives me a difference of up to 0.5ph just because of wall colour.

 

[Bol]

Do you mean you used the same vial of solution, and checked it against the two charts simultaneously?

If that's the case, then ... you probably shouldn't. From the test kits I've seen, the two tests are meant to use different solutions.

If you used two separate solutions, and got different results, I'd tend to believe the high-range one, as 7.6 is pretty much the top of the scale for "regular" pH tests, while 8.0 is midrange for the high-range test. But, as tca said, I'd probably re-test just to be sure.

p.s. I also find that natural daylight is the best for reading color charts.

 

[jiffy]

Thanks for all the tips. I ill try retesting and check it in differnet lights and repost. I used 2 different vials, and 2 differnet solutions, not checking the same vial against 2 different cards.

 

[jiffy]

Ok, I retested with the high pH and checked it in different lights. It looks like its about 8.0 I think Bol is right about 7.6 being the top range for regular pH, so It must not darken any more than that. I guess if you get a 7.6 you should move on to the high pH test to see if it is in that range.