Formulation of Lipsticks

Depending on who you speak to, lipsticks can either be simple to formulate or very complicated. In my opinion they are a little of both. Simple because it is one phase made up of waxes oils and colors with some fragrance and preservatives thrown in. Complicated because there are so many things to track with such a simple formula - sweating, melting, stick hardness & shine, feathering, wear time, good mold release, flaming, etc., some of these can be very difficult to trouble shoot. Some attributes that a consumer would look for in a formula would be an easy to apply luxurious application with even color lay down and nice shine, an elegant creamy long wearing product which is non-transferring and non-staining and in a wide range of colors. This describes the ideal product that is also cost effective and readily available at any cosmetic counter.

From a formulation standpoint, that ideal lipstick is made up of waxes and oils that are all compatible with one another. The predominant oil is usually food grade castor oil which is a very good solvent for pigment wetting and grinding as well as solubilizer for waxes and other ingredients in the formula. The level of castor oil will vary depending on the level of colorants, pearls and other fillers, and the other ingredients in the formula that are used to arrive at the products specific characteristics. There should be enough castor oil in the formula to sufficiently disperse the pigments for grinding and enough after this for rinsing the 3-roll mill or ball mill and final color adjustments. The final level of castor oil can be as high as 50% and is usually the first material listed on the ingredient label.

The other ingredients in the formula are waxes, oils and fillers. The waxes in many cases are natural vegetable waxes such as candelilla wax and carnauba wax both used for stick hardness and shine. An example of this wax functionality would be carnauba which is used in furniture polish and car wax. However, too much of these waxes will make a stick too brittle. Another wax that is very much used in lipstick is beeswax. This wax is also naturally derived and is excellent for stick shrinkage and good mold release. Other lesser used waxes but just as important are Japan wax, ceresin wax, ozokerite, montan wax, microcrystalline waxes, paraffins, and to some degree, polyethylenes. The mineral waxes such as ozokerite, microcrystalline and ceresin add elasticity and help plasticize the stick structure. They can also be combined to create a specific melt point and hardness target. There should be some flexibility for the stick as it is applied on the lip, otherwise it may snap if too much pressure is applied on application. The optimum level of waxes depends on the solvency and solubility of the other ingredients and the desired hardness of the formula. This level can range from 15 to 25% total waxes depending on their individual melt points. Modifying and reducing the wax levels will bring you closer to lip gloss formulations.

There is a huge selection of oils that are used in a lipstick formula. The most common are vegetable oils and esters. The vegetable oils are good solvents also aid in the wetting and dispersion of the pigments ad pearls. These can be avocado oil, olive oil, sesame oil, wheat germ oil, or some other exotic oils. These oils and esters also are excellent emollients and moisturizers. Esters are reaction products of fatty alcohols and fatty acids. The number and combinations are almost limitless. They can be solids, liquids, pastes with high, low or medium viscosity high or low skin penetration and many other characteristics that are desired to arrive at the final stick feel, function and application. Also used in lipsticks are high molecular weight alcohols such as octyl dodecanol and lanolin derivatives. These also act as solvents and couplers and are very good for solubilizing those not so compatible ingredients. The level of these ingredients can be as high as 25-30% in the final formula.

The ingredients just mentioned are the backbone of every lipstick. A good indicator of how good your lipstick will be in terms of ingredient compatibility would be when you mix all the ingredients together and heat them to 75-80º C the mixture should be crystal clear. This means that all the ingredients are soluble with one another at elevated temperature. This is a good sign as there are no incompatibilities with any of the ingredients you are using. One group of ingredients that a formulator should stay away from are silicone compounds or powder surface treatments utilizing silicone coatings. Although silicones are great for feel and skin protectant OTC claims, they will adversely affect the stick appearance and this will become very visible when flaming the stick. There will be an abundance of craters on the stick surface as soon as the stick is exposed to an open flame.

Other ingredients that are used in lipsticks are fragrances, flavors and preservatives. Fragrances and flavors will vary depending on the requirements of the brands, marketing, and product positioning. The levels used depend on whether you are using natural or synthetic flavors and fragrances. This is due to cost and function of the various ingredients chosen. Depending on the type of formula, the level of fragrance or flavors can be as high as 10%. These are also used at lower levels just to mask the waxy odor and taste of the lipstick base.

Preservatives are essential for any cosmetic formulation. Although lipsticks are anhydrous and can be heated to at least 85-90º C (or higher) sometimes for extended periods of time, they contain no water and are thus hostile environments for the growth of microorganisms. Bugs will just not grow in them. However, they should contain preservatives to protect the product for when it gets into the hands of the consumer, or to protect the product in case the lipstick package itself may contribute to microbial growth. There are a number of preservatives that can be used but these can vary depending on the formula. Some preservatives of choice are propyl paraben, butyl paraben and phenoxyethanol. These are all oil soluble preservatives and work well in hot pour anhydrous formulations. But no product should ever be over preserved. Use the recommended levels in accordance with supplier recommendations and regulatory acceptability.

One thing we haven't mentioned here, and the main constituent of lipstick, is colorants and pearls. I have talked about this subject at length in many previous articles, so all I have to say here is that the levels of colors and pearls in a lipstick formula varies with the pay off that is desired and the amount of color deposit on the lip that is characteristic of a certain brand name of product. The color level in some lipsticks can be as high as 20% or more but my personal opinion is that this level of color only adds to the cost of the formula and may make the formula too dry. While 8-10% dry color is suitable for lip tints, 12-15% dry color should work well for full coverage lipsticks. Pearls can be used at higher levels for effect. But it's your formula so you be the judge. Let's leave it to your creativity.