Glycerin and Humidity

Cindy asks a winter inspired question from frigid Wisconsin where humectants are making the winter of 2014-2015 even more frustrating. You need to know that here in the Midwestern U.S.A. (like Wisconsin), winter tends to be very cold and very dry. So even when we see the outdoor humidity is, say, 50%, if the temperature is 10°F (-12°C), the air is still extremely dry and the dewpoint - that temperature indicating how much water the air could hold if it was fully saturated - could be below 0°F. That is desert-dry air.

I zero in on glycerin because it can be a curly or wavy-haired person's dry-air nemesis. But I didn't leave many out, so read on. "Humectant" is a very broad category including salts, glycerin, plant gels like aloe vera or flax gel, algae extracts, hyaluronic acid, hydrolyzed proteins, sodium PCA, lactic acid, urea, witch hazel (without alcohol) and other ingredients that attract water. Not all humectants are "created" equal - different humectants behave differently in hair. I think when people complain about humectants, they are having the most trouble with simple humectants like: glycerin, propylene glycol, sorbitol.

Humectants attract water to themselves. Humectants like glycerin are great at grabbing water vapor out of the air. When you have a hair gel with glycerin in it, when there is ample water in the air (humidity) - the air is going to be hydrating the glycerin in the product, which is going to help your hair stay hydrated. Well-hydrated hair has more bounce and definition. A second benefit of glycerin in products (when there is ample water vapor in the air) is that glycerin keeps hold-providing ingredients that would otherwise create a brittle, candy-like finish from feeling brittle and candy-like. Glycerin (and sorbitol and propylene glycol) take water vapor from the air to hydrate the dry gel in your hair and keep it more flexible.

When there isn't enough water vapor in the air (low humidity and/or low dewpoints), the gel loses that benefit from the glycerin and the gel becomes more brittle, creates friction and that means hair that feels dry and crusty and looks dull.

Whether humectants actually dehydrate the hair - pull water from the hair is not well-studied. And it is an "it all depends" sort of question. It is based on a reasonable hypothesis; that if glycerin attracts water from the air, when the air is drier than your hair, water will move from your hair to the glycerin. For that matter, when the air is less humid than the inside of your hair - the water will tend to move from your hair to the air around it - glycerin or not. So does glycerin create a stronger "pull" (water gradient) than dry air alone? It probably does exert a stronger pull on the water in your hair than dry air alone. But not all humectants do that. Think of glycerin like brown sugar. In humid air, a bag or tin of brown sugar absorbs moisture and forms clumps. But it dries out quickly too and the clumps become hard as a result.

Don't discount the effect of that dehydrated gel sitting on your hair because 1) glycerin can't pull enough water out of your hair to keep a gel from getting brittle and 2) brittle gel creates friction - that means rough, tacky hair that frizzes when it contacts other hairs and objects and snags at cuticle edges. A crusty, dehydrated product in your hair is bad news for how your hair looks and feels.

Mitigating circumstances

If you used oil or leave-in conditioner under a glycerin-containing product, that layer of emollients would slow down water loss from hair. If there are other humectants that are not a ready to give up their water as glycerin in the same product, the effect might be reduced. Oils and conditioners act as "occlusives" - the layer of oil or leave-in conditioner is not water-soluble and that helps slow the movement of water in and out of hair.

Why glycerin, why must you be so fickle?

To get to the heart of why glycerin can be a problem ingredient for some people in some weather, one big issue is the size of the molecule. The smaller the molecule, the less water it can bind and hang on to when exposed to very dry air. Glycerin, sorbitol and propylene glycol are "sugar alcohols" - not alcohol like the kind used in hairspray. They are small molecules. There are not a lot of places on the molecule to bind water. Think of glycerin as a "simple sugar" as you would think of candy. Sure, glycerin and sorbitol and propylene glycol aggressively pull water to themselves, but they also lose it fairly easily. Emollients (oils and conditioners) can slow that down, but not stop it. So when the air is very dry - glycerin is a much less effective ingredient. Glycerin is a fair-weather friend. When the humidity is just right, glycerin can help your hair look and feel great. When the weather gets too dry, glycerin can't pull enough water to itself and it loses it's effectiveness. When the air is very humid and glycerin pulls lots and lots of water in - poof - your hair loses definition. 

Glycerin is a small molecule and not
very complex.

Formulation can be a problem

Often, a problem with a glycerin-containing product is that it uses only glycerin for a humectant and "flexibilizer" and does't use any emollients or film-forming humectants at all. Well-balanced products avoid this pitfall. Different humectants have different actions and a combination of different size and molecular weight humectants might be okay for a person who finds that just glycerin and no emollients or film-formers is a mess.

Is it just me?

There are people who live in climates that are dry year-round and use glycerin with no problems at all. And there are people who can only use glycerin when the humidity is "just right." There is no simple rule to determine how your hair will respond because it's not just a porosity issue. It's an issue of climate and weather, what other products you use in your hair, how sensitive your hair is to increased friction, how often you go outdoors. Trial and error. As usual. 

Is there a winter-proof (dry-weather-proof) humectant?

A great big molecule like the complex carbohydrates in flax seed gel or hydrolyzed proteins behave differently in hair than glycerin. These ingredients don't rely heavily on water vapor to work well. They don't have aggressive water-grabbing force. They're more subtle. There are many places to bind water in these molecules. Not only that, but they also form clear, flexible films over your hair. Water-hugging films that tend to slow water loss from the hair. If these large, moisture-retaining humectants which I call "film-forming humectants" are combined with oils or conditioning ingredients in a styling product, the humectants and oils and/or conditioning ingredients combine to actively attract and hold water and slow water loss, providing longer-lasting hydration and lubrication. The link in the previous sentence takes you to a list of film-forming humectants.

One of the many complex carbohydrates
in flax and other plant gels. It is a larger
molecule and more complex, capable of
forming water-hugging films.

Hair that cannot tolerate simple humectants like glycerin or propylene glycol may still do well with film-forming humectants in styling products. What we want from styling products is extremely personal. If you are looking for hold or definition, these are some styling products which may work:

AG Weightless Volumizer

AG Mousse Gel

AG Re:Coil

Aussie Real Volume Mousse

Aussie Instant Freeze Gel

Camille Rose Aloe Whipped Butter Gel

Curl Junkie Curl Queen

Curl Junkie Pattern Pusha

Biosilk Rock Hard Gelle

Darcy's Botanicals Curling Cream Gel

DevaCurl Set Up and Above

Goddess Curls Gel

Herbal Essences Totally Twisted Curl Scrunching Gel

Herbal Essences Set Me Up Gel

Herbal Essences Naked Volumizing Souffle

Jessicurl Confident Coils Styling Solution

LA Looks Nutra Curl Moisturizing Gel

Salon Care Aloe Vera Styling Gel

Pantene Pro-V Stylers Max Hold or Strong Hold Gel

For products that are based on film-forming humectants, including many natural and plant-based gels, go to  this page on this blog and scroll down to the list of products including film-forming humectants. Some contain glycerin - check the ingredient lists. Most are light to medium hold and can be topped with a gel with stronger hold, like Biosilk Rock Hard Gelee (from the above list) if necessary.

Why are plant-based, film-forming humectants less "fickle?" Stuff about plants.

Flax seed is an example. The gel comes from water contacting the seed. Seeds do this so that when they are in the soil and the soil is moist, the seed can attract water, form that gel which assures the seed will stay moist enough to sprout. If a seed gets wet, begins to sprout and then dries out, it dies. So this is a brilliant adaptive strategy to assure seeds sprout to create new plants and more seeds.

With aloe vera, that is a desert plant. It has thick, leathery leaves with spines on them to discourage animals from eating the juicy leaves and to prevent water loss. The gel in the inner leaf does not dry out quickly, a good strategy for a desert plant.