Hopewell Valley Student Podcasting Network
Chemistry of Cosmetics
Welcome to Chemistry Connections, my name is Sydney Yeh and my name is Hannah Chu and we are your hosts for episode 12 called Chemistry of Cosmetics. Today we will be discussing the chemistry of cosmetics.
Segment 1: Introduction to Cosmetics
What are cosmetics?
There are thousands of different cosmetic products on the market, all with different combinations of ingredients. In the United States alone, there are approximately 12,500 unique chemical ingredients approved for use in personal care products. A typical product could contain anything from 15–50 ingredients. Considering the average woman uses between 9 and 15 personal care products per day, researchers have estimated that, when combined with the addition of perfumes, women place around 515 individual chemicals on their skin each day through cosmetic use.
(History of cosmetics)
Let’s take it back to cosmetics in the olden times. Cosmetics were first seen in ancient Egypt, where makeup served as a marker of wealth believed to appeal to the gods. The elaborate eyeliner characteristic of Egyptian art appeared on men and women as early as 4000 BCE. Kohl, rouge, white powders to lighten skin tone, and malachite eye shadow (the green color that represented the gods Horus and Re) were all in popular use. By 3000 B.C men and women in China had begun to stain their fingernails with colors according to their social class, while Greek women used poisonous lead carbonate to achieve a pale complexion.
Segment 2: The Chemistry Behind Cosmetics
A huge range of substances are used to create many appealing colors found in makeup. Mineral ingredients include iron oxide, mica flakes, manganese, chromium oxide, and coal tar. Natural colors can come from plants, such as beet powder.
Cosmetic pigments are broken up into two types, organic and inorganic.
Inorganic pigments consist of iron oxides, chromium dioxides, ultramarines, manganese violet, white pigments, and pearlescent effects. They are used for their opaque color coverage, making them particularly suitable in face and eye makeup. They are usually duller in appearance than organic pigments. The transition metals in inorganic pigments form colorful ions, complexes, and compounds. This is due to the unfilled d orbitals these elements have. When transition metal ions form complexes and compounds with other molecules, they become colored. They bond to one or more neutral or negatively charged nonmetals, also known as ligands (li gens), changing the shape of d orbitals. Unabsorbed wavelengths of light pass through a complex and some light is also reflected back from a molecule. The combination of absorption, reflection, and transmission results in the apparent colors of the complexes.
Shimmering effects can be created by coating mica with titanium dioxide and iron oxides to vary the refractive index observed in the finished product. Cosmetic mica typically comes from muscovite, also known as white mica. It naturally forms in flaky sheets, which are crushed into fine powders. The tiny particles in the powders refract (bend) light, which creates the shimmering effect common in many cosmetics. Various thicknesses of titanium dioxide are used to vary the color effects that are created through the different refractive angles that are created. These refractive angles can also manipulate the visual effects of the finished products. Additionally, iron oxides combined with the titanium dioxide coating can create a two-tone or luster effect. A variety of metallic and bright colors can be created using the pearlescent coating effect.
- Emulsions are also common in the chemistry of cosmetics. The majority of creams and lotions are emulsions. An emulsion can be defined simply as two immiscible fluids where one liquid is dispersed as fine droplets in the other. Typically, creating a lotion or cream takes three phases: a water phase, an oil phase, and a finishing phase that occurs after your emulsion has cooled.
- But, oil and water don’t mix. This is because water is a polar molecule – its structure means that is has a positive charge one end and a negative charge the other end. Water molecules stick together because the positive end of one water molecule is attracted to the negative end of another. However, the structure of an oil molecule is non polar. Its charge is evenly balanced rather than having one positive and one negative end. This means oil molecules are more attracted to other oil molecules than water molecules, and water molecules are more attracted to each other than oil, so the two never mix.
- Since water and oil do not mix but stay separated, an additional agent (emulsifier) is necessary to form a homogenous mixture keeping water and oil together. Without an emulsifier, you can mix the water and oil together but as soon as you stop, they fall out and separate back to oil floating on water.
- In cosmetic chemistry, we use ’emulsions’ to blend two immiscible (unblendable) liquids together. An emulsifier stabilizes an emulsion by increasing its kinetic stability. Emulsifiers work because their molecules have two parts: one part is attracted to water and one part is attracted to oil. There are two types of emulsions: Oil in Water and Water in Oil. An oil in water emulsion is composed of an oil phase dispersed in an aqueous one. It is known as a direct emulsion. Stabilization of O/W emulsion is often performed with hydrophilic-hydrophobic particles. The hydrophilic end of the emulsifier molecule has an affinity for water, and the hydrophobic end is drawn to the fat/oil. By vigorously mixing the emulsifier with the water and oil, it creates a stable emulsion. And then the water in oil emulsion is composed of an aqueous phase dispersed in the oil phase.
Segment 3: Personal Connections
We are one of the many women that wear makeup and use cosmetics, as we have many chemical ingredients on our bodies right now! I have about 273 chemicals (Sydney) in my body, and I have 219 chemicals (Hannah) in me. It is important for us to be cautious about what ingredients we put in our bodies, along with the types of chemicals and how they could affect us. In addition, it is important to know how some of the products we put on our faces are made.
Thank you for listening to this episode of Chemistry Connections. For more student-ran podcasts and digital content, make sure that you visit www.hvspn.com.
Warm Nights by @LakeyInspired