[Natsoft]

Since pH strips don't always work discolor well with thick hair products (conditioners and creams), I want to use this pH sensor to measure the pH of hair products. Since I understood that this pH sensor is not designed for creamy-but-water-based products but rather for aqueous solutions, how much should I dilute the cosmetic product? And how should I calculate the pH if I used a dilution (my basic chemistry knowledge is a bit rusty )?

On a side note, I also want to measure the hair product dissolved in tap water (pH 8.0, but free of chlorine and heavy metals) besides DI water to get a more realistic representation.

[Borek]

In general there is no way of telling how the dilution changes the pH without knowing exact composition of teh mixture.

Best thing you can do is to try several different dilutions and see how the pH changes, then attempt to estimate pH of the undiluted product. Changes can be relatively small, as most likely pH is buffered.

[billnotgatez]

Would the series of dilutions be
1 ml of stuff in 10 ml of water (distilled)
1 ml of stuff in 100 ml of water (distilled)
1 ml of stuff in 1000 ml of water (distilled)

[Borek]

Would the series of dilutions be
1 ml of stuff in 10 ml of water (distilled)
1 ml of stuff in 100 ml of water (distilled)
1 ml of stuff in 1000 ml of water (distilled)

Can be, doesn't have to be. 1:2, 1:4, 1:8, 1:16 makes sense as well, or 1:5, :25, 1:125 and so on. Actually you don't even hot follow any easy to reproduce pattern, 1:5, 1:30, 1:123 would do as well. What matters is that you know what you did, you cover the range and you plot the results correctly.