Dear Valerie:
What’—H2 Oh-No

Dear H2:
Every geography is different in terms of tap water composition. Normally, tap water, meaning, unfiltered city water, contains high amounts of metals such as calcium, magnesium, copper, zinc and iron. We often hear of tap water being soft or hard. This is in reference to the amount of calcium and magnesium it contains. Soft water contains less, hard water contains more. Numerous studies have been done to look at the impact of metal ions in tap water on skin and hair.

Calcium is the most preferred metal for hair to absorb because, even though it’s not as small as magnesium, it has a larger atomic radius. Therefore, the outer electrons can interact more loosely with anionic sites on hair. Calcium inhabits the whole hair fiber, although mostly the cuticle layers, where the hair is damaged, which is a sign of environmental exposure. The more the hair is damaged, the deeper calcium can penetrate.

The interesting thing is, no matter how hard or soft the water, there was still the same amount of metal uptake in hair for soft water as hard water.¹ This is because hair has a finite amount of space for the metals to bind. The only influencing factor is how damaged the hair is. Virgin hair has a minimal amount of binding in both hard and soft water, colored hair next, and then the most amount of metal uptake is in bleached hair. This makes sense because damaged hair is negatively charged, and there are only so many anionic binding sites available on the hair. 

The pH of water also plays an important role; alkaline water has been shown to increase binding of metals to hair, which makes sense, because an alkaline state increases the amount of negatively charged binding sites on hair.
Aside from just sticking to hair, calcium and magnesium can form water-insoluble soaps, much like your bathtub gets soap scum. This leaves hair feeling stiff and looking dull, and forms a film on skin.

Of course, these aren’t the only ions you need to worry about for hair—copper can be troublesome.² Copper can be found in plumbing or water heaters, and anywhere from the water treatment facility to your shower head, although most plumbing is not copper anymore. Tap water has very low levels of copper, but copper is highly affinitive for the hair. Considering hair can grow for years on your head, the copper ions build up in low levels and accumulate in the fiber. Copper is reactive and can catalyze reactions that damage hair protein, making it break, less shiny and harder to manage and even causing split ends. An example of one reaction is when you bleach or color your hair; any copper ions react with the hydrogen peroxide radicals in the hair and damage the fiber. 

Copper is also found in excessive levels in swimming pools. Most people think chlorine is responsible for turning their hair green. It’s actually copper, as it oxidizes and creates a green patina. Chlorine and its effect on hair has been studied at least since the 1970s or 1980s.³ Chlorine exists in tap water at a maximum of 4ppm. There was a thorough study done in the 1980s where researchers studied the effects of 10ppm of chlorine on the hair. They found that over time, up to 30 washes, hair exposed to chlorine suffered cuticle loss and was dry at a neutral pH.

Hair isn’t the only thing impacted by minerals in water—skin is affected too. Tap water in the US varies between pH 6.5-8.5, although it averages around 7.5. In the EU, it’s slightly higher at 8.0. This increases skin’s native pH up to six hours after application, before returning to its natural value (on average, below 5). Skin with pH values below 5.0 is in better condition than skin with pH values above 5.0.⁴ Additionally, skin in an acidic state (4–4.5) keeps the resident bacterial flora attached to the skin, whereas an alkaline pH (8–9) promotes the dispersal from the skin. This could lead to barrier issues.

One researcher from the University of Sheffield⁵ led a study exploring the effects of hard water on skin’s outer barrier. This study evaluated a simple SLS solution on skin and found that increased mineral content in water deposited more SLS onto skin. As a result, patients with eczema were much more sensitive to the effects of hard water, versus healthy skin individuals. Furthermore, another meta-study⁶ confirms that hard water exposure contributes to development of atopic eczema in children.So, should consumers really worry about hard water? For the most part, no. If you have healthy hair, the hardness of water doesn’t really impact the health or appearance; if it’s chemically processed, that’—Gummy Gal

Dear Gummy:
In the lab, it may be convenient to pre-disperse a gum like xanthan gum or guar gum into a slurry, where the powdered thickener is premixed with a solvent. This is a convenient method that prevents clumps or fisheyes from forming in your vessel—you simply just pour it in. Otherwise, you need to ensure adequate mixing and incorporation of the thickener through sprinkling or sifting.

Unfortunately, there is no specific best practice for this. Some manufacturers may not have the appropriate equipment to disperse thickeners in a lump-free process, so they are happy to create a premix to incorporate the slurry into the main vessel. Other manufacturers despise multiple premixes, since it requires additional equipment, sanitation and transfer. They would rather sift the thickener into the tank through old-fashioned means. Or, they may have the dispersal equipment necessary to adequately incorporate the thickener in the batch, sans premix.

Since there is no universal method of incorporation, and it’s based on the capabilities of the manufacturer, I would just “do you” during the lab processing—use what can be repeated consistently in the lab. Then, work closely with the manufacturer during the tech transfer process to see which method works best for them, based on their equipment, expertise and ability. 

References:

1. Evans AO, Marsh JM, Wickett RR. The uptake of water hardness metals by human hair. J Cosmet Sci. 2011;62(4):383-391.
2. Smart KE, Kilburn M, Schroeder M, et al. Copper and calcium uptake in colored hair. J Cosmet Sci. 2009;60(3):337-345.
3. Fair, N., & Gupta, B.S. (1987). The chlorine-hair interaction. II: Effect of chlorination at varied pH levels on hair properties. Journal of the society of cosmetic chemists, 38, 371-384.
4. Lambers H, Piessens S, Bloem A, Pronk H, Finkel P. Natural skin surface pH is on average below 5, which is beneficial for its resident flora. Int J Cosmet Sci. 2006;28(5):359-370. doi:10.1111/j.1467-2494.2006.00344.x
5. Danby SG, Brown K, Wigley AM, et al. The Effect of Water Hardness on Surfactant Deposition after Washing and Subsequent Skin Irritation in Atopic Dermatitis Patients and Healthy Control Subjects. J Invest Dermatol. 2018;138(1):68-77. doi:10.1016/j.jid.2017.08.037
6. Jabbar-Lopez ZK, Ung CY, Alexander H, et al. The effect of water hardness on atopic eczema, skin barrier function: A systematic review, meta-analysis. Clin Exp Allergy. 2021;51(3):430-451. doi:10.1111/cea.13797

---

Valerie George
[email protected]
 
Valerie George is a cosmetic chemist, science communicator, educator, leader, and avid proponent of transparency in the beauty industry. She works on the latest research in hair color and hair care at her company, Simply Formulas, and is the co-host of The Beauty Brains podcast. You can find her on Instagram at @cosmetic_chemist or showcasing her favorite ingredients to small brands and home formulators at simply-ingredients.com