In this post, Weekend Wonderings: Have a question", Valerie asked: Are there guidelines on to dilute (with distilled water) a sample of a product before testing to get ph test accurate results - like shampoo, lotion etc. I have pH tested my liquid soaps in the past and was instructed to dilute appropriately before testing to get accurate results. Any advice is appreciated! I have made a powdered foaming exfoliating cleanser that I would like to pH test. I have a digital reader and a know how to calibrate it using the solutions. Also, I would love to post this recipe for feedback and suggestions on how to improve it.
I've been using the method put forth by Kenna of Modern Soapmaking. "I?m aiming for a 1% soap solution, meaning 1% of the solution is soap and 99% of the solution is distilled water. To make it easy, I weighed approximately 1 gram of soap and 99 grams of distilled water..."
If you're using distilled water - which should have a pH of 7 or neutral - then the only change to the water is the thing you want to measure. So using as little as 1% should be enough to alter the pH enough to be measured. I generally use 10% as I usually have my 1 gram scale handy versus my tinier scale, so I use 10 grams product to 90 grams distilled water. 
Why do we have to dilute our products" It's obvious in the case of a shampoo bar or solid soap, but this is important for anything that's thicker than water as the electrodes aren't equipped to measu...