CurlChemist examines the delicate balance between humidity, dew point and humectants and your curls
As we head into springtime, many curlies apprehensively anticipate the return of humidity — and frizz.
Weather is a constant variable that can toss a kink into the best of hair days. Who among us hasn't left the house with perfectly coiffed curls, only to step out into a hot, sticky afternoon or a damp, foggy morning and see our hair lose all recognizable shape, inflate to twice its normal size and develop the texture of a piece of steel wool?
Wouldn't it be spectacular if there was some crystal ball that could tell us each morning what the weather patterns would be and what exact products to use that would enable us to circumvent this seemingly unavoidable hair disaster? Although that might not be realistic, there are some clues available to us in the morning weather report or on NaturallyCurly's Frizz Forecast. Learning some basic facts about humidity, humectants and the dew point can arm you with the the knowledge you need to select the right types of products to keep your curls looking their best, whether the weather is bone dry or warm and muggy.
50 Ways to say "Humidity"
I am neither a meteorologist nor an expert in the thermodynamics of gaseous mixtures, but I am going to tackle this topic even though it makes my brain hurt. Water coexists in the atmosphere with the gaseous mixture (primarily oxygen and nitrogen) that makes up our air. We all are aware of the fluctuating levels of moisture in our air — especially those of us living here in the great southern swamplands of the United States.
A description of the moisture content in the air can be expressed using different terms and based upon various calculations. The two most familiar to us are relative humidity and dew point, which are both typically disclosed in our local daily weather report. Even armed with all this information, it can be confusing for one to understand just exactly how humid it is.
Relative humidity expresses the relationship between the vapor pressure or vapor density (g/m3) of the water in the air at a specific temperature versus the saturated vapor pressure of water at that temperature.
RH = (actual H2O vapor pressure/saturated H2O vapor pressure) x 100
The saturated vapor pressure for water changes substantially with temperature. So as the temperature increases or decreases, the value for relative humidity changes, even if the overall water content in the air remains unchanged.
Example: We have an actual vapor density of 6.6 g/m3, and a temperature of 86°F. The saturated vapor density for water at this temperature is approximately 30.4 g/m3. This gives a relative humidity of approximately 21.7 percent. If the temperature increases to 98.6, the saturated vapor density increases to 44 g/m3, and the relative humidity becomes 15 percent. Conversely, if the temperature were to decrease substantially to 55°F, the saturated water density decreases to 11.35, and the RH increases to a value of 50 percent! If the temperature is gradually decreased to approximately 37°F, the relative humidity approaches 100 percent.
(See this site for a great chart and all sorts of additional information).
Oxygen and nitrogen are always gases at the temperatures found in our atmosphere, and the molecules bounce around in the air exhibiting ideal gas behavior (conforming to certain thermodynamic laws). Water, with its relatively high boiling point, exists in all of its phases at our atmospheric temperatures. Primarily, in our atmosphere, it is constantly exchanging between its liquid state and its gaseous state. One way of thinking about dew point is that it is the temperature at which the number of gaseous water molecules being formed is equal to the number of liquid water molecules being formed (Evaporation rate = condensation rate). When the temperature reaches the dew point, the relative humidity is 100 percent. If the temperature decreases below the dew point, water must condense out of the air, and fog, dew, or clouds are formed.
We can see by a quick review of our previous example that had we chosen a greater value for our actual water density (meaning a higher level of water in the air), our relative humidity values would all have been higher, and our dew point would also be shifted to a higher value.
So we can conclude that a higher value for our dew point necessarily means a higher concentration of water vapor in the atmosphere, and a lower dew point means less moisture is in the air.
A common question among curlies is at which dew points are humectants helpful and desirable, and at which dew points are they perhaps harmful and undesirable? Before answering that question, let's review humectants and touch on "anti-humectants" as well.
We have spent significant time in the past discussing the chemical and physical nature of humectants and their relevance to the health and beauty of curly hair. To summarize quickly, humectants are molecules that possess atoms and groups of atoms that attract and bind water to themselves. They can have benefits and drawbacks for curly hair, and their performance is often very dependent upon the amount of moisture in the environment. This variable performance is due to the driving force in nature to reach and maintain a state of equilibrium.
Dry hair, placed in a wet, humid environment, quickly absorbs water from the air. Unprotected hair can quickly lose all of its internal moisture and become very dry in an arid environment. Humectants applied to the hair draw water to themselves from whichever source is greater — the atmosphere or the hair.
For more in-depth information on this topic, read this article.
What is an Anti-humectant?
An ingredient may be called an anti-humectant if it fulfills several requirements. First, it must not be hygroscopic, meaning it must not possess molecular traits that cause it to attract water molecules to itself. Second, it must be water repellent, which necessarily means insoluble in water. This property allows it to lock out or prevent the intrusion of moisture into the hair from a humid environment. Additionally, these ingredients typically coat, flatten, and seal the external cuticle layer of the hair strands. The anti-humectant ingredient will most likely be higher on the list of ingredients, and may be problematic for those on a shampoo free routine.
In many formulations, the ingredients used for this anti-humectant task are silicones. This is because they not only perform the anti-humectant duties in a superior manner, but they also provide excellent lubrication of the hair and add a high degree of gloss (shine). Esters (such as isopropyl palmitate) are another category of ingredient used for their water-resistant properties in products designed to function well in high humidity climates. There are also many natural ingredients that work well for this purpose, such as hydrogenated castor oil, beeswax, and plant triglycerides such as coconut oil, palm oil, olive oil, and shea butter. I have included the ingredient lists for three different hair pomades and anti-humectant products that I found interesting.
MOP Glisten High Shine Pomade
Ingredients: Aloe Barbadensis Leaf Juice, Hydroabietyl Alcohol (Gum Rosin), Hydrogenated Castor Oil, Caprylic/Capric/ Stearic Triglyceride (Coconut/Palm), Beeswax (Cera Alba), Lanolin, Hydrogenated Rosin (Pine Tree Sap), PEG-40 Hydrogenated Castor Oil, Cocos Nucifera (Coconut) Oil, Lanolin Wax (Lanolin Cera), PEG-8 Beeswax, PEG-10 Soy Sterol (Soy), Butyrospermum Parkii (Shea Butter), Wheat Germ Glycerides, PEG-60 Almond Glycerides, Limnanthes Alba (Meadowfoam) Seed Oil, Olea Europaea (Olive) Fruit Oil, Humulus Lupulus (Hops) Extracts (3), Urtica Dioica (Nettle) Extracts (3), Cymbopogon Schoenanthus Extract (3), Fragrance (Parfum), Methylparaben, Ethylparaben, Propylparaben, Butylparaben, Phenoxyethanol, Isobutylparaben. [Source: (1) CertifiedOrganic in accordance with the California Food Act of 1990. (3) Certified Organic by Quality Assurance International.]
Hair Pomade by John Masters Organics
Ingredients: Extra virgin olive oil, organic beeswax, mango butter, babassu oil, jojoba, wheat germ oil, pure essential oils of bay laurel, cedar atlas, fir balsam and massoia, vitamins A, C & E. Certified Organic Ingredients.
Aveda Brilliant Anti-Humectant Pomade
Ingredients: Caprylic/Capric Triglyceride; Isopropyl Palmitate; C18-36 Acid Triglyceride; Bis-Diglyceryl Polyacyladipate-1; Bis-Diglyceryl Polacyladipate-2; Castor (Ricinus Communis) Oil; Phenyl Trimethicone; Cyclomethicone; Fragrance (Parfum); Glyceryl Laurate; Rice (Oryza Sativa) Bran Oil
The Relationship Between Humectants and Dew Point
It would be great if there were a magical mathematical formula to tell you exactly which ingredients to use in which temperature and humidity conditions. The best I can do is provide you with some loose recommendations on that topic. As always, you will need to do some experimentation with your own hair to find the combination of conditions and product that give the results you prefer.
If the dew point is below 35°F or so, the moisture content in the air is sufficiently low that a humectant applied to your hair might be irresistibly drawn to the moisture in your hair and make every attempt to steal it from you (by drawing it out of your hair and binding it to itself). This can result in dry, fly-away hair, split ends, and broken strands. This effect can often be compensated for by using plenty of moisturizing products, not over-drying your hair (leave it somewhat moist after washing), and layering leave-in conditioners with humectant-containing styling product.
Curly hair seems to really thrive in moderate climactic conditions, and dew point ranges of approximately 35°F to 50°F seem to be optimal. In this type of weather, most curlies find that they can get really pleasant results by using products that contain some humectants. There is just enough moisture in the air that the humectants can grab a little from the environment, which can enhance the curl and create a bouncy feeling to the hair.
When the dew point for your area is at 60°F or above, it might be a good idea to apply some product with anti-humectant properties. These products will seal the hair shaft, flatten the cuticle and prevent atmospheric moisture from absorbing into the interior of your strands. Most of these products will contain ingredients that are water insoluble. However, many of these products contain ingredients which are easily removed with an extremely mild shampoo or perhaps even a thorough conditioner wash.
The key to having the best curls in any weather is to have extremely well-hydrated and moisturized hair. This will protect your hair from losing too much moisture in dry weather, and it will prevent your hair from absorbing excess moisture in humid conditions. Another important factor is the overall condition of your hair. Hair that is damaged will necessarily be more porous, and thus more susceptible to climactic conditions. Smooth strands with a sealed, flat cuticle layer will be naturally more impervious to atmospheric conditions as well.