This is to teach people some general information about hair that we all should know. If anyone has questions let me know.

Okay we are gonna start with the parts of the hair. There are 3 parts of a human hair. the innermost part is called the Medulla. The middle layer is called the Cortex. The Cortex contains all the stuff like hair color pigments known as Melanin. The outer layer is the Cuticle which is made up of a bunch of tiny fish like scales.

Now we are gonna discuss the word Porosity. Porosity is the ability of hair to absorb liquids. The term porosity refers to how many holes or Pores the hair has. In other words how Porous is the hair? In order to explain porosity I came up with a simple way. Lets say you have 3 blocks of wood. One block of wood is smooth and does not have any holes. The second block has 5 holes drilled into it about halfway. The third block has about 20 holes in it. The block with no holes is the least Porous. The block with 20 holes is very porous. Now lets say we have 3 separate cups filled with 1 cup of water each. If we pour water on the smooth block it will soak into the wood but it will take forever. If we pour the water on the 5 holed block it will soak in fairly fast. If we pour the water on the 20 holed block it will soak in super fast. Now Your hair is like these blocks of wood. One hair strand might have all three degrees of porosity ranging from least porous at the scalp and most porous at the ends. The reason is because your ends have been exposed to the elements longer.

Now about those elements, acids and alkalies. The pH scale is a scale that tells whether something is acid or alkaline. It ranges from 0 to 14. 0 - 6.9 are called acids, 7 is neutral, and 7.1 - 14 are alkalies. When you look at a pH scale the closer to 0 or 14 you get the more damaging it is to your hair. The closer you are to 7 the better it is even though it may still damage your hair.

Acids close the cuticle layer (the scales). Alkalies open the cuticle and attack the cortex. Bleach, Ammonia, Relaxer are all alkalies. Acids can be things like vinegar or lemon juice or anything that says acid. Battery Acid aka Hydroflouric is 0 and Stomach Acid aka Hydrochloric is 1

When you perm or relax your hair you apply a solution that contains an alkaline. It opens the cuticle and then it enters the cortex and attacks the disulfide bonds in your hair. These bonds are what hold your hair in its shape. When you apply a perm solution or relaxer you let it process for awhile and then you apply a neutralizer to stop the processing and to close your cuticle. If you don’t apply a neutralizer the perm or relaxer will not stop eating away at your hair and your hair will be dissolved.

There are also acid perms and the way those work is instead of using chemicals they use heat to do the work.

Okay now if you understand that alkalies open the cuticle and that acids close it then we can proceed. Getting back to porosity, it is the main factor in figuring out what kind of perm or relaxer to use. Relaxers and Perms come in different strengths. There are mild, regular, and super. Okay now super works the fastest and mild works the slowest. As I stated if you leave the relaxer or perm on too long it will eat your hair. Now you have to think of it in terms of applying it to the whole head which means if you apply it to the right side and then its eating the hair on the right side before you are done with the left then you have to find a slower acting solution. The speed of the action is determined by how fast the hair soaks up the solution or the Porosity. The more porous the hair is the slower you want the processing to be. So using our blocks of wood as an example, the no holes block would need a Super strength solution, the 5 holed block would use the regular, and the 20 holed block would use the mild.

Now back to acids and alkalies. There is no such thing as virgin hair because any hair that is outside of your head is exposed. We now know that acids close the cuticle and alkalies open it. Water is 7 on the pH scale and is neutral however tap water has things other than water in it such as minerals or fluoride or maybe even chlorine. Lets say you are cleaning your windows with window cleaner and you are misting it on the window. Window cleaners contain ammonia and that’s an alkaline so if that gets on your hair its gonna open your cuticle and attack your cortex. Now lets say you are making orange juice or lemonade by squeezing fruit and you accidentally squirt your hair with the juice. The juice is called citric acid and being an acid its going to act like one on your hair. Remember acids that are close to 0 on the scale are more dangerous so just because they close the cuticle that doesn’t always mean that’s a good thing. If the acid is too strong it will eat the cuticle and shrink your hair into nothing. Now lets say you never perm or relax or color your hair. You are still exposed to everything in the air and in the water so your hair is being exposed to things that are opening and closing your cuticle repeatedly. If your cuticle gets too much exercise its going to not want to go back in its proper place and that’s how you get frizzy hair. If you open and close a book a bunch of times sooner or later the book doesn’t close flat. I’ve heard people ask about dry ends. The reason your ends are dry are because they have been around the longest and exposed to too much opening and closing and soaking things up and they are really porous now. The more you soak things into the hair the more porous it gets. That’s why when you tell someone that you have tried conditioning the ends and they aren’t getting any better. Its because its gotten to the point that they can’t soak it up and hold it in anymore. The way to explain that is lets say you pour the water on the 20 holed block and it soaks in but then you tip it over so the holes face down (like hair with an open cuticle) the water is going to drain out of the wood and the oil that was in the wood will drain out too. Now this isn’t necessarily the end of the battle. If you can get that cuticle smoothed out and stop letting the liquids out then it won’t be so dry. That’s why vinegar works. Its an acid and it will close your cuticle. Its not guaranteed to work because if you have scales on your cuticle that are bent out of shape and they won’t close completely then there is still possibility of loss of moisture.

Source: http://www.angelfire.com/mi/bbubba/LHC/GI1.html