In the article on spignatto we mentioned the topic pH: let's see what it is here.
The pH in do-it-yourself cosmetics
The pH is a scale ranging from 0 to 14 and which measures the acidity and basicity of an aqueous solution based on the concentration of hydrogen ions present in it; a pH between 0 and 6 is acid, from 8 to 14 it is basic while the value 7 indicates a neutral pH.
The pH is an important aspect for those who prepare their cosmetics at home: in fact, our skin has a slightly acid pH. Although the skin is able to buffer pH changes, applying basic or too acidic products on it tends to stress it over time and this can cause problems.
Cosmetics must therefore have a slightly acidic pH. In the list below we see the values that should be included in the cosmetics we prepare.
Facial products
Creams: 5.5-6.0
Cleansing milk: 6-7
Tonic: 4.5-5.5
Exfoliants: from 3.5 to 4.5
Eye contour cream: 6.0
Body products
Creams: 5.5
Bubble bath and shower gel: 5.5-6.5
Intimate cleanser: 4.0-4.5
Shampoo: 4.5-5.0
Balm: 4.5
Deodorant: 4.0-5.0
Exfoliants: from 3.5 to 4.5
How and when to measure pH in DIY cosmetics
The pH is measured only when our cosmetic has an aqueous phase so it should not be measured in lip balms, scrubs, ointments that contain only oils, butters and waxes, etc.
If instead our cosmetic contains water (emulsion creams, detergents, tonics), once the preparation is finished we will have to measure the pH.
To measure pH in the laboratory, the piaccametro is used , while in the home environment the pH indicator papers (litmus paper) are used; the map is immersed in the product for at least 30 seconds, after which the value is compared with the table that is supplied at the time of purchase.
The maps are sold in pharmacies or on Internet sites specialized in the sale of DIY natural raw materials.
How to lower or raise the pH of DIY cosmetics
Recalling that a pH lower than 7 is acid, equal to 7 is neutral and above 7 is basic:
if the product we have made has too high a pH it will be necessary to acidify, whereas if the pH is too low it will have to be based.
To acidify the cosmetics, lactic acid is added little by little, measuring the pH value every three / four drops added up to the desired pH.
In order to base the cosmetics, caustic soda (Sodium hydroxide) in solution is used instead. The caustic soda solution is sold ready-made on Internet sites that sell raw materials for DIY cosmetics but can also be prepared at home, with appropriate precautions.
After wearing a mask, gloves and protective glasses, 20 g of caustic soda and 80 g of distilled water are weighed, then pour the caustic soda into the water, mix and, once dissolved, pour the solution into a glass bottle.
At the time of use it is added to the preparation a little at a time until reaching the desired pH, measuring the value every three / four drops added, as already seen for lactic acid.
Attention : caustic soda is a strong base that in contact with water produces irritating vapors and heat. It is important to wear the precautions listed above and to use heat-resistant glass, plastic or stainless steel containers and the action of basic substances.
Should the caustic soda solution come into contact with skin and / or eyes, rinse immediately.
Remember to affix a label to the bottle indicating the danger of the solution, to prevent someone accidentally confusing it with water.
