How and when should I be using glycerin based hair products?

By . - Monday, November 04, 2013

Dew Point

The Dew point is the temperature at which the water vapor in air begins to condense to a liquid.  It is an absolute measure for how much water vapor is present in outside air.   The greater the dew point temperature, the more water vapor available to condense into liquid water.  Conversely, the lower dew point temperature corresponds to lower amounts of water vapor available to condense into liquid water.  A good rule of thumb for dew point is as follows:

  • Humid Conditions            60F to +80F

  • Optimal Conditions          40 F to 60F

  • Dry/ Arid Conditions       Less than 40F


 Now, moving on to Glycerin-I’ll discuss the technical definition of glycerin, how it’s made and its function in hair care products.

 Vegetable glycerin is a colorless, clear, viscous liquid (it has the consistency of molasses) that is extremely water-soluble.  It is produced from the hydrolysis of coconut and palm based glycerol fats with water under high temperature and pressure.  The product is then distilled to remove the excess water to produce glycerin at +99.3% purity.  It is primarily used as a humectant in cosmetics and personal care products. 

Now you’re probably asking, what is a humectant?

Humectants have two primary functions in hair products: It absorbs water from the air and slows down the rate at which water evaporates from your hair.  In other words, in hair products, glycerin brings the hair shaft in contact with water and limits the water’s ability to evaporate.  Thus, your hair has a greater chance of absorbing water and staying hydrated, which is the key to having healthy hair and minimizing breakage.   Therefore, having a humectant in your hair products is advantageous but, as I hinted above, there are trade offs, especially for curly hair because it tends to be more porous and will need the extra moisture to stay hydrated.  The key to getting optimum performance from glycerin based products is using them at the correct dew point temperature.

Now that you know the definition of dew points and glycerin, let’s discuss the effect they have on your hair- or more specifically, what is the correlation between and dew points and glycerin?

Glycerin Based Products in Low Dew Point Climates

Under dry, arid conditions, glycerin struggles to find enough water in the air to properly hydrate itself (remember glycerin needs water and will therefore, bind to it).  Thus in arid conditions, the only benefit that glycerin will give your hair is that it will slow down the evaporation rate of water from your hair back into the environment.  Simultaneously, glycerin will struggle to remove the small available amount of water from the arid air.  However,  once all the available free water is consumed from the air, the glycerin in your hair product, will then remove the available water from the product itself.  Once that is gone, it will remove the water from the cortex of your hair because glycerin is a humectant and needs to stay hydrated.  Needless to say, using products formulated with glycerin is counterproductive to achieving healthy hair when applied in arid conditions. It leads to overall dryness, coarseness, frizz, fly-aways and an increased probability for greater damage by causing split ends.

Glycerin Products in High Dew Point Climates

Under humid conditions, glycerin causes the hair to become over saturated with water and therefore, disrupts some of your hair’s structure/hydrogen bonding.   I don’t want to get into the chemical structure of hair in this discussion, but I must digress so that you’ll get the complete picture.   Again, when hydrogen bonding is disrupted, your hair losses some structure. Don’t be alarmed because every time you shower, shampoo or go into a high humidity climate, you are disrupting hydrogen bonding in your hair.   When you wet your hair, you are breaking hydrogen bonding.  Your hair looses structure and becomes elongated.   During the drying process, water evaporates and the hydrogen bonds reform.  Your hair’s natural structure is reformed and the hair elongation is reduced so it goes back to its natural state.  This is called shrinkage.   Also, during the elongation process, the hair becomes swollen and the cuticle raises, which causes tangling. Hint, this is why your hair gets tangled when you wash it.

Now, having explained the process of water/humidity with respects to the elongation and shrinkage of your hair, let’s take closer look at glycerin.  The problem with using glycerin based products in high humidity is that it slows down the drying process and increases the chances of damaging your hair while it is elongated.   When your hair is wet or elongated, it is weaker and more prone to breakage.  Obviously, using glycerin based products in humid climates consistently keeps your hair in an elongated state.  Therefore, it increases the probability of damaging it. It can also lose its curl pattern and become frizzy due to having swollen cuticles and tangling, as I mentioned above.  Lastly depending on the concentration of glycerin in the product, your hair might begin to feel stickier.

So, what’s the optimal time to use glycerin products?

  1. Only use products with high glycerin concentrations during optimal dew point temperatures (40F to 60F).

  2. Use Glycerin free products for humid conditions.  In particular, look for the polyquats to detangle and address frizzy hair (typically in the summer and dew point is above 60F)

  3. Use leave-in or deep conditioners (standard oil/water emulsions) for low humidity conditions, which is typically in the winter and dew point is below 40F)

 Please note that products formulated with low levels of glycerine, will not have these dramatic effects on the hair and to best “guestimate” glycerine levels, look for products that list glycerine on the back end of the ingredients list.

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