pH of your skin & checking pH of store brought skincare products
So one of my subscribers wanted to know about the pH and myths around it, hmmm I thought what a great content idea so here I am discussing about the pH of you skin and alos checking the pH of store brought skincare products
We will talking about the following points in this article
- What is pH?
- pH of your skin?
- pH ranges idea for cosmetic formulation
- What is pH meter?
- How to check pH in cosmetic products?
- Buffer solution
- How to calibrate pH meter?
Also check out the article about Hyluronic acid
What is pH?
pH – “Potential of Hydrogen” some people love to call it “Power of Hydrogen” please get the pun intended.
pH scale was devised in the early 1900’s by a Danish Chemist SPL Sorensen for measuring acidity and alkalinity.
It is a figure expressing the acidity or alkalinity of a solution on a logarithmic scale on which 7 in neutral, lower values are more acidic and higher values are more alkaline.
The pH is equal to –log10 C, where c is the hydrogen ion concentration in moles per liter. Ions are molecules that carry positive or negative charge.
Some examples of pH
- Water – pH 7
- Blood – pH 7.4
- Sea water – pH 8
- Baking Soda – pH 9.5
- Milk – pH 6.3
- Lemon juice – pH 2
pH of skin
Our skin is made of layers and the top layer of the skin is called as Epidermis.
Epidermis has a major gland which gives the characterist of acidicity to the skin.
We have sabecous glands that produce sebum. Sebum contains natural salths and lactic acid which help to maintain the natural slightly acidic nature of our skin. This sebum breaksdown fatty acids and form a protective layer or film on the skin which is known as Acid Mantle
Ninety years ago – in 1928, the term acid mantle was coined by the physicians Heinrich Schade and Alfred Marchionini in Kiel, Germany.
Ideal pH of the skin is pH – 4.7 – 5.75
pH of the skin varies slightly according to the gender & where it is on the body. It also fluctuates at different stages of life.
Men’s skin tends to be more acidic as they sweat more and more sebum is produced.
When we are born our skin has neutral pH and becomes acidic in a couple of weeks of birth.
pH range for cosmetic formulation
Cleanser = 4.5 – 7
Toner = 5 – 7
Sunscreen = 5 – 7.5
AHA & BHA = 3 – 4
Moisturizers = 4.5 – 5.5
Serums = 4 – 6
Vit C products = 2.6 – 3.2
Retinol = 3.7 – 5
What is pH meter?
The quantitative information provided by the pH measurement expresses the degree of the activity of an acid or base in terms of hydrogen ion activity.
The pH value of a substance is directly related to the ratio of the hydrogen ion [H+] and the hydroxyl ion [OH-] concentrations.
If the H+ concentration is greater than OH-, the material is acidic; i.e., the pH measurement is less than 7.
If the OH- concentration is greater than H+, the material is basic, with a pH value greater than 7. If equal amounts of H+ and OH- ions are present, the material is neutral, with a pH of 7.
Acids and bases have free hydrogen and hydroxyl ions, respectively. The relationship between hydrogen ions and hydroxyl ions in a given solution is constant for a given set of conditions, either one can be determined by knowing the other.
pH Measurement tools
pH measurement papers.
A rough indication of pH can be obtained using pH papers or indicators, which change color as the pH level varies.
These indicators have limitations on their accuracy, and can be difficult to interpret correctly in colored or murky samples.
More accurate pH measurements are obtained with a electronic pH meter.
A pH measurement system consists of three parts:
- a pH measuring electrode,
- a reference electrode
- ahigh input impedance meter
. The pH electrode can be thought of as a battery, with a voltage that varies with the pH of the measured solution.
The pH measuring electrode is a hydrogen ion sensitive glass bulb, with a millivolt output that varies with the changes in the relative hydrogen ion concentration inside and outside of the bulb.
Buffers are solutions that have constant pH values and the ability to resist changes in that pH level.
They are used to calibrate pH measurement systems (electrode and meter).
There can be small differences between the output of one electrode and another, as well as changes in the output of electrodes over time.
Therefore, the system must be periodically calibrated.
Buffers are available with a wide range of pH values, and they come in both premixed liquid form or as convenient dry powder capsules or tablets.
Most pH meters require calibration at several specific pH values.
One calibration is usually performed near the isopotential point (the signal produced by an electrode at pH 7 is 0 mV at 25°C), and a second is typically performed at either pH 4 or pH 10.
It is best to select a buffer as close as possible to the actual pH value of the sample to be measured.
How to calibrate your pH meter?
Here is a general method for most pH meters. Some pH meters require slightly different techniques. Please read the instructions for their particular procedures.
- The temperature setting on the meter must correspond to the temperature of the buffers used, or an automatic temperature compensator must be employed.
- Turn pH meter to “pH” or “ATC” if automatic temperature compensation is used.
- Place clean electrode into fresh, room temperature pH 7.00 buffer.
- Adjust the pH reading to exactly 7.00 using the ZERO OFFSET,STANDARDIZED or SET knob.
- Rinse the electrode with distilled or deionized water. (This would be the procedure for a one-point calibration. Continue through step 8 for a two-point calibration.)
- Place electrode into the second buffer, either pH 4.00 or pH 10.00.
- Adjust the pH reading to display the correct value using the SLOPE, CALIBRATE, or GAIN controls (coarse adjust).
- Adjust the pH reading to read the correct value using the SLOPE knob (fine adjust)
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