What is pH?
The scientific definition of this value is: “The pH value is the negative decimal logarithm of the hydrogen ion concentration” and is therefore a measure of the acid concentration in aqueous solutions. The pH value indicates how acidic or alkaline a solution is. The pH scale goes from 0 to 14.
Acids have a pH below 7 and bases above 7, the mean value of pH 7 is called neutral . You can measure the pH with indicator solutions, indicator paper or with a pH meter.
Examples of different pH values (rounded)
- 1 – Gastric juice, battery acid
- 2 – lemon juice
- 3 – vinegar
- 4 – cola, sauerkraut
- 5 – skin, mineral water
- 6 – Milch
- 7 – distilled water, blood
- 8 – Darmsaft
- 9 – soap
- 11 – detergents, ammonia
importance for the skin
A pH value can also be assigned to the skin, since the hydrolipid film on the skin’s surface contains water. It was already known a hundred years ago that the skin is slightly acidic. With modern measurement methods, it was found that the average pH value of the skin is between 5.4 and 5.9.
How does this value come about?
Horn scales, sebum, sweat and microparticles together form an acidic environment. One also speaks of the so-called protective acid mantle of the skin. This protective coat helps to ward off harmful microorganisms and negative environmental influences and thus protect the skin from infections, irritation, allergies and dehydration.
With each cleaning with soap, this protective layer is lost and the physiological balance of the skin is disturbed. The pH value of the skin is raised to around 9 for a short time. However, healthy skin manages to reduce the value to normal again within 30 to 200 minutes.