It’s a very good question, why do I need to know about pH? and one that has been asked by several of my hairdressing pals, so this blog is for you and anybody else who’s interested. Don’t worry; fortunately, through the combination of knowledge, product development and even regulations you can blissfully practice your Professional art without the need to get all pH geeky, the manufactures have done all the hard work for you. But if you want to know more please read a little further.
What is pH
pH stands for the power of hydrogen or potential hydrogen; it all depends on how you translate it. But everyone agrees that pH is a measure of hydrogen ion concentration, a measure of the acidity or alkalinity of a solution. The pH scale usually ranges from 0 to 14. Aqueous solutions at 25°C with a pH less than 7 are acidic, while those with a pH greater than 7 are basic or alkaline. Yes, there are some very strong acids and alkaline that are literally ‘off the scale’, thankfully we don’t use or need them in the beauty industry.
We work with many acids (low pH) and bases (high pH) every day. Examples of pH values of hair products includes
- Semi-Permanent Acidic Colours & Conditioners can sit between pH2 –pH4.5
- Water is pH7
- Hydrogen Peroxide pH1 – 5 depending on the dilution and stability additives; generally, the lower the concentration the milder the acidity, e.g. 3% is approximately pH4-5.
- Demi Permanent Colour = pH 9-10
- Permanent Colour = pH10-11
- Bleach = pH9-11
- Standard Perms & Straighteners = pH 8-9.5 (Thioglycolic/cystine)
- Standard Perm & Straightener neutraliser = pH2.5
- Acid Perm = pH7-8
- Relaxers = pH 12 (Lye & no Lye versions)
Not All Liquids Have a pH Value
pH only has meaning in an aqueous solution (in water). Many chemicals, including liquids, do not have pH values. If there’s no water, there’s no pH. For example, there is no pH value for natural oils or pure alcohol.
How pH is Measured
Rough pH measurements can be made using litmus paper. These papers are useful to tell whether a substance is an acid or a base or to identify pH within a narrow range. More accurate measurements happen in a lab, using a pH meter.
Uses of pH
pH is used in everyday life as well as in hairdressing. It’s used in cooking (e.g., reacting baking powder and an acid to make those lovely cakes and breads rise), to design cocktails, in cleaners, and in food preservation. It’s important in pool maintenance and water purification, agriculture, medicine, chemistry, engineering, oceanography, biology, and other sciences.
pH and hair
Hair and scalp have a pH anywhere between 4.5 and 5.5 which means they are acidic. This range is normal for hair and skin and we continue to change the pH regularly without even thinking about, like when we wash our hair; water has a pH of 7 so it will have an influence on the hair but as soon as we dry it the hair will come back to its normal pH. You will notice that when hair is wet the pH is affecting its behaviour, like when we comb wet hair it feels rough, it stretches, or it can snap/break more easily.
When the hair’s pH is normal it is instrumental in making the cuticle layers lie flatter, which makes hair smoother and shinier as the flat layers reflect light more evenly. Layers that lie more snugly against the hair shaft also prevent moisture loss more efficiently, which helps hair to be stronger and healthier.
But we do a lot more to our hair than simply wash and dry it. The key point to remember with pH is balance; when we move the hair’s pH from one extreme to another, we always need to return it to its normal pH. When we manipulate the hair’s pH, we can change its appearance either temporarily or permanently, fortunately, nature will always find its balance so, no matter what we do to the hair it will eventually return to its normal pH, but that can only happen when the hair is dry.
As professionals we should consider the occasions when we wet hair. I come back to the previous example of washing the hair. You will have heard or read the phrase pH balanced in relation to shampoos and conditioners. Water will have an influence on the hair’s pH and to mitigate the negative effects manufactures formulate care products in order to keep the hair as close to its normal pH during the washing and drying process; the reason is to prevent damage, remember the hair is in a weaker state when wet. You can test it yourself; after wetting your hair apply a conditioner to one side, now take a strand of hair from each side and stretch it, (you don’t have to pull it out that would hurt). You will notice that the side without the conditioner will stretch more and break faster than without; this has nothing to do with friction but everything to do with pH.
When looking for a big change; colouring, bleaching , texturizing the rule of thumb is the greater the change on or in the hair the greater the change in pH is required. This is primarily for two reasons 1) to create pathways for the chemistry to enter the hair and 2) for the environment within the hair to be the correct pH for the chemistry to work, otherwise it would be like putting a cake in the oven without turning on the oven; apologies for all the baking analogies, but I do love to bake.
pH and wet services
Professionally all of our services you can classify as wet services making them pH relevant from shampooing, perming, straightening/relaxing, colouring and bleaching. Taking the example of bleach; the hair will be treated with a wet product (typically you mix a powder with a liquid to form a paste) with a high pH 9-10 making it an alkaline. This allows the bleaching chemistry to enter into the hair’s cortex through softened and swollen cuticles and create the right environment for the bleaching mechanism to work on the hair’s melanin. Any pH shift will also affect the structural bonds in the hair so care should be taken not to overly stress the hair unnecessarily; check out my other blogs on bleach chemistry, usage and care. After the bleach has done its job of dissolving the melanin the product is rinsed off and the hair’s pH is lowered but as it is wet it will not return to its normal pH by itself. It is important to work with a post-bleaching treatment to return the hair closer to its normal pH before proceeding with any additional services. In the case of bleach, it might be a toner or another colour, which again shifts the pH into a higher alkaline range.
Open for debate; there has been a lot of discussion among Chemists, Professionals and Educators on the right way to treat multiple steps in hair. One side of the argument is to keep the hair ‘open’ at a higher alkaline and complete all of the steps required prior to closing down the hair OR to shut down each individual chemistry returning the hair as close as possible to a normal pH before moving onto the next step.
Personally, I am on the latter side of the debate as I believe it is important to not only bring the hair back as close as possible to its starting pH, after all this is where product development is based from but also to shut down any residual previous chemistry that might affect the next chemistry applied.
Don’t be fooled by all things acidic been better for the hair; that is not entirely true, the acidity needs to be close to the hair’s pH, if too acidic it can negatively influence the hair, by making it harder and more brittle. Example; colour protecting shampoos are mildly acidic typically sitting around pH4.5 if too low the shampoo can start to remove some of the artificial colour from the hair. You may see chemicals such as citric acid or sodium hydroxide or triethanolamine towards the end of the ingredient list (INCI), these are added in very tiny amounts in order to adjust the pH of the product to the proper level.
However lower pH can be used advantageously, ascorbic acid pH2.5 (vitamin C) not only is a great anti-oxidant it can also be used very safely to remove some dyes from the hair; the is how Wella’s Colour Renew or Malibu Crystals work.
pH – who needs to know
Everything pH is a must know when formulating products for hair and scalp; the pH needs to be perfect in order for the chemistry to work and within safety limits for the well-being of the client and professional. As Professionals do we need to fully understand pH? the simple answer is no, as that has been taken care of by the manufactures however, it is good to know about pH as it helps us to make informed decisions about products, join the debates and to take necessary steps to protect the integrity of the hair and scalp with work with.
Caroline
