Wednesday, 5 May 2010
Q: Is the pH strip faulty?
A: I doubt it. Most commercially bought strips work well and have a long shelf life especially if stored somewhere dark.
Q:How accurate are pH strips?
A: In science pH strips are used to give a rough indication of the pH. There are really accurate machines used if doing a proper study and these can measure the difference between pH of 6.988 and 6.989 (yes really!). Commercial strips do tend to measure the difference between 1 value like pH 6 and pH 7. This means if you have a pH of 6.5 it may look like 6 or 7 or something in between. In short pH strips are not the most accurate but are accurate enough for many applications.
But some pH paper comes in half values too, is that better?
A:You can purchase anything you like but really if you just want to use it to test your hair products increments of 1 are fine.
Q:So why the different values on the same product?
A: Having eliminated errors with the pH strips, I must therefore assume user error. Here are some key facts
1. Only substances that can dissolve or consist of water can give you a pH. The slightly more complicated answer is that pH is related to the concentration of charged groups in water (for super geeks - look up hydronium ions).
*Science Quiz: Can you test the pH of coconut oil? Correct answers get a virtual cookie
2. You cannot test the pH of a solid and solids (even tiny little undissolved particles) can interfere with pH testing . This means you cannot just place your conditioner directly onto the strip and expect an accurate result. Hair conditioner is not really a true liquid. You should dissolve it into water (as little water as possible) and then test it. Solids can interact with the paper and give you a false result . However if you have a glycerin/water mix or apple cider vinegar, you can use these direcly as they are solutions.
*Top Science Hint - If it is a solution a general rule is that you can see through it because there are no particles.
3. Keep your hands out the mix. Our hands are huge sources of chemicals - natural oils, soap, lotion etc. If you want a consistent result, DO NOT use your finger to place the testing object (for example water mixed conditioner) onto the strip. Ideally if you have a glass rod use this, if not use a clean spoon
4. If you need to dissolve something to do your test, use clean glass. Plastic tends to leach into the solution and metal can react with the solution. Clean means washed with soap thoroughly and then rinsed three times in water and allowed to dry naturally. Three is the magic number for scientists. It is enough to show that you made some effort, anything more is welcomed but three is the magic number.
*Final Science Quiz: Given hair is a solid, how come it has a pH? Correct answers get a virtual natural haven medal
Are you struggling with pH or pH strips? If so, ask a question and I will try and help!