| A | B |
|---|
| Three layers of hair strands | 1. cuticle 2. Cortex 3. Medulla |
| Cuticle | Outermost layer, overlapping translucent scales, protects the cortex, porous/water loving, opens and closes |
| Cortex | Middle layer, strongest part of the hair strand, represents 85% of the total weight, made of twisting fibers, keratin, melanin, 3 side bond-hydrogen, salt, disulfide |
| Hydrogen Bonds | Ionic (-/+), weak bond, broken by heat and moisture, easily rebuilt, most numerous, account for 1/3 of the hair strength |
| Salt bond | Ionic (-/+), weak bond, broken pH changes, fairly easily rebuilt, moderate in numbers, account for 1/3 of the hair strenghth |
| Disulfide Bonds | Covalent (shares chemical makeup), Strongest bond (linked by two sulfur atoms), broken permanent chemical changes, difficult to rebuild, least numerous, 1/3 of the hair strength |
| Medulla | Innermost layer, composed of soft keratin and air, fine hair may not contain it, coarse hair has a lager medulla |
| 5 atoms that are the building blocks of and acid molecule | C-carbon H-Hydrogen O-oxygen N-Nitrogen S-sulfur |
| Protein | 65-95% gives hair strength enght |
| Moisture | Up to 32% hair ability to stretch |
| Lipids | Glue holding protein together |
| Chemical makeup of hair | Protein, moisture, lipids, melanin |
| Two types of melanin | Eumelanin, Pheomelanin |
| pH scale | 0-6.9 acidic, 7 neutral, 7.1-14 alkaline |
| Healthy hair | 4.5-5 |
| PH scale | Indicates the amount of hydrogen ions (H+) and hydroxide ions (OH-) in a solution |
| What’s an ion? | An atom with an electron imbalance |
| Negative ions | Repel and push against each other, opening and swelling the cuticle |
| Logarithmic | Increase or decrease change of concentration by a tenfold |
