Porosity refers to the hair's ability, or inability, to absorb water or chemicals deep into the cuticle layers and cortex. All hair is naturally porous and somewhat permeable to water.
Low or "poor porosity" refers to hair that does not readily absorb moisture and resists chemical treatments. Poor porosity is not exactly a problem that should cause you great concern. It is, however, ideal to have hair that falls somewhere in the middle of the two porosity extremes: hair with good porosity that retains moisture well and accepts chemical treatments.
Our hair has the ability to absorb up to 50% of its weight in water! This absorption and lengthening is why wet hair feels heavier than dried hair. Think of a sponge. When the sponge is fresh and new, it is able to absorb a good amount of water and hold the moisture inside very well. As the sponge ages, the pores become distorted, the fabric of the sponge is weaker, and it begins to lose its shape. Because the old sponge cannot hold the amount of water it once could, it is said to be more porous or have higher porosity than the new sponge.
The following questions will help you determine whether or not your hair is overly porous:
Does your hair continuously soak in moisture without ever actually feeling moisturized?
Is your hair chronically dry despite your best conditioning efforts?
Does your hair appear/feel puffy, frizzy, swollen, or tough to the touch?
Does your hair have a natural, reddish toned cast to it that is usually more pronounced in spring and summer time?
Does your hair hold styles and curl well?
If you've answered yes to any of the above hair characteristics, and these characteristics appear more pronounced toward the ends of your hair, you may have a problem with your hair's porosity level.
Causes of Porosity Problems
There are two main conditions that aggravate the physical integrity of the cuticle layer, and thus, the hair's porosity level.
The first is soundness of each cuticle scale along the hair strand.The soundness of the cuticle scales refers to the smoothness of each individual hair scale surface. Weak or damaged scales are often worn, cracked, and may even have holes in them. The more damaged an individual scale is, the more porous that scale will be.
The second is the general spatial arrangement of the cuticle scales relative to one another. Lifted scales are porous simply because they are not lying flat against the others. They will let moisture out easily. The unavoidable constant lifting and closing of the cuticle layers over time through regular washing, conditioning, and chemical processing increases the overall porosity of the hair. The ends of the hair are typically the most porous because the cuticle layers in this region have simply been opening and closing the longest. If the individual scales are porous, and the scales are lifted up and away from one another, the porosity situation is compounded.
So what exactly damages the cuticles in those ways?
Specifically, hair porosity is affected by excessive exposure to:
mechanical and heat abuse from combs, brushes, and heat styling tools,
and the continued use of sodium lauryl or ammonium lauryl sulfate-rich shampoos.
Porosity Problems for the Relaxed and Color Treated
Relaxing or colored treating the hair with chemicals forces the cuticle layers up and open. Unfortunately, when this happens, these chemical treatments increase the porosity of the hair by both means: by degrading the cuticle layers and causing them to lift dramatically. In time, the cuticle layers do eventually close on their own, but if the damage is repeated too often by either back to back coloring jobs, heat overuse, or relaxing too frequently those cuticle layers may never close fully again. For this reason, relaxed and color treated individuals should be extra diligent about managing their hair's porosity.
It is best to measure your level of porosity on freshly cleaned and dried hair.
Test 1: Wet your hair. Before you start to shampoo your hair, notice how long it takes for your hair to actually feel soaked and fully saturated with water. Hair that "wets" easily is typically porous. If your hair takes quite some time to actually get fully wet, your hair is less porous. (Or your hair could be coated with heavy oils and other products!) As your hair dries (air dry), note how quickly the drying takes place. Porous hair dries very quickly, and in some cases, the ends of the hair may be dry before your body is fully dried! Hair that takes longer to dry is typically less porous.
On fully dried hair, note whether your hair feels rough and tangles easily. Hair that "catches" on itself, does not move well, and tangles easily is usually porous, or is in need of a trim.
Test 2: Gently hold strands of your dry hair between your index finger and thumb, and then slowly slide your fingers along the length of the strand. You should be moving from the scalp to the ends. If you feel an overall uneven texture as you move along down the shaft, your hair is slightly porous.
Test 3: Take a few strands of "harvested" hair (shed hair from your comb, hair brush, etc.) and place them in a bowl of water. If the hair sinks in less than a minute or two, it is porous. The sooner your hair sinks, the more porous it is. If only one part of the strand sinks, you have a spotty porosity problem. This is not uncommon.
Once you have performed one or more of the porosity tests and believe that your hair is indeed porous, read Part 2 of this Porosity Series to learn ways that you can treat your own porosity issues.