The first and foremost ingredient to be considered in the formulation and manufacture of face powder is talc. Talc is the softest material on the Mohs scale of hardness. Chemically, it is a magnesium silicate, 3MgO.4SiO2.H2O and is the basic ingredient of face powder formulation. Its outstanding properties are easy spreadability (slip) and low covering power.
An extensive variety of talc is available and it should be judged on the basis of slip, smoothness, fineness, grit, density, color and odor. For face powder use, talc should be white and virtually odorless with a smooth greasy feel with excellent slip properties.
Kaolin or china clay is a generic term, which is applied to several hydrated aluminium silicates. Kaolin is naturally mined product derived from feldspar. It possesses good covering power and adhesion as well as certain grease-resistant and perspiration-absorbent properties. Kaolin helps to remove the shine of talc and has certain soothing effects on the skin.
All aluminium silicates cannot be classified as kaolin. There are three distinct groups of clay which have essentially the same formula, Al2O3.2SiO2.2H2O and may be called kaolin: nacrite, dickite, and kaolinite.
The color of kaolin used should be as light as possible (slightly off-white to pale cream colored) and kaolin should be highly purified and free from gritty impurities and coarse particles. Since kaolin is hygroscopic, its use in face powders does not normally exceed 25%. Kaolin, like talc, is a innocuous material.
In face powder formulation and manufacture, a good cosmetic grade precipitate chalk serves to preserve a certain balance between slip and adhesion, covering power and transparency.
A grit free precipitate chalk or calcium carbonate (CaCO3) is mildly alkaline, white, odorless, microcrystalline powder and it reduces the shine of talc and has a good covering power, its helps to absorb the perfume and is also grease resistant and perspiration absorbent. It is also excellent for developing the bloom effect when face powder is applied. If this raw material is used in excess, the powder may acquire a dry feel, but moderate usage is most helpful to face powder formulas.
The valuable characteristics of magnesium carbonate make it a commonly used ingredient in face powder. MgCO3 has fine absorbent properties and has been proven satisfactorily as a means of distributing perfume. The MgCO3 used should be fine in quality and free from contamination and a moderate amount of MgCO3 is used, since use in excess may result in drying effect on the skin.
Among the metallic stearates, zinc and magnesium stearates are most widely used. For face powder, the stearates must be of highest quality to avoid the development of rancid, disagreeable odor.
The most important characteristics of zinc and magnesium stearates are their adhesive and water proofing properties. Zinc stearate, the most commonly employed, also possesses a soothing quality. Used in excess stearates may create a smeared, blotchy effect on the skin. In moderate amounts (4-15%) zinc stearate contributes to the adherent qualities of a face powder.
Zinc oxide and Titanium oxide:
Since one of the primary function of the face powder is to mask minor skin blemishes, covering power must receive careful consideration. There are two basic opacifiers employed in face powder formulas: zinc oxide (ZnO) and titanium dioxide (TiO2). Too much coverage by either may produce a mask like effect which is undesirable; too little gives a powder with insufficient body.
Zinc oxide possesses moderate adhesive properties and is comparatively inert. Zinc oxide has certain therapeutic properties and helps to clear up minor skin disorders. When employed in face powders, it should be of high quality as white color as possible. Odorless, uniform, fine and free from grit. Excessive use of ZnO may result drying effect. To avoid any drying effect and allow sufficient coverage, a formulation may consist as much as 25% ZnO.
Titanium dioxide (TiO2) is three to four times better as a covering agent than ZnO, but it has less adhesion and cannot be blended quite as well. For a face powder with a desired covering power a blend of this two is necessary.
The use of rice or wheat starch was a basic face powder ingredient; its current activity is limited. The bloom and adsorbent properties of starch make it useful ingredient. As starch is decomposed by bacterial action, it is now replaced by calcium carbonate and other materials.
Silicas and Silicates:
Silicas and silicates maintain free flowing characteristics of face powder even at high humidity. Silicates also serve as perfume carriers. Magnesium trisilicate is also used.
Frosted look materials:
Natural pearlessence (guanine) consists of needlike, colorless, and transparent crystals which, by simultaneous reflection and transmission of incident light on their platelets, impart a pearl luster. Pearlessence exhibits extreme light-stability.
The synthetic pigment bismuth oxychloride was developed to replace guanine. Although photosensitive, bismuth oxychloride is quite adaptable for use in frosted face powders to impart a metallic, pearl-like luster. Metallic powders (mica, aluminium, bronze) are widely used to formulate powders with sheen.
Inorganic pigment or organic lakes or toners are used. The opacity of the oxides and transparency of the talc greatly influence the quantity of color needed. The color that used must be Food, Drug and Cosmetic Act (FDCA) certified grade.
The selection of proper perfume is of extreme importance, since the odor of powder plays an important role in the sales potential of the product. The perfume that used must be non-irritating, stable to mildly alkaline condition and not undergo oxidation or volatilization easily. The fragrance must be compatible with all of the powder ingredients since problem with rancidity, heterogeneity of odor, and discoloration may results from improper odor selection.