Oils, fats and waxes: the differences in cosmetic formulation

Oils, fats and waxes: the differences in cosmetic formulation

Oils, fats and waxes are used in many cosmetic formulations for skincare, haircare and body products. When choosing your ingredients with your cosmetic chemist, there are some issues to be considered, such as natural and synthetic options, limitations with formulation, and issues that can arise during the formulation process.

What are oils, fats and waxes?

An oil is a moisturising ingredient made of glycerine and various fatty acids and is liquid at room temperature. 

Fats are very similar to oils, except they are solid at room temperature. 

Waxes are usually solid, more brittle and often have a higher melting point than fats and oils, though some natural waxes are in semi-solid or liquid form.

How are natural oils, fats and waxes produced?

Plant or vegetable oils and fats are extracted from the oil-bearing parts of the plant — usually the seed, nuts or fruit. The plant material is cleaned, pressed and heated to extract the oil or fat. This extraction can then be refined to remove undesired fatty acids, or bleached or deodorised to remove unwanted colour or scent.

Animal fats, oils and waxes are largely produced by rendering, which breaks down the cellular structures of animal by-products. 

Rendering can be done 'wet' or 'dry'. 

Wet rendering uses a steam injection that heats the animal material to extract the oils, fats and waxes. This can produce higher quality extracts, but is more time consuming.

Dry rendering heats the animal material to a higher temperature and agitates the material to prevent charring. As the material cooks in its own moisture, the fats, oils and waxes sink to the bottom of the vat.

Natural waxes, such as beeswax and lanolin are processed differently. 

To extract beeswax, combs are melted under steam, heat or boiling water so that the wax can be separated.

Lanolin, the waxy substance from wool-bearing sebaceous glands, is extracted by scouring wool in hot water and removing the wax by centrifugal separators.

What are synthetic oils, fats and waxes?

Synthetic oils, fats and waxes are distilled from petrochemicals. Crude oil is heated to high temperatures and, as the temperature of the oil rises, various groups of compounds boil off. Eventually, a tar-like mass of compounds with very high boiling points is left behind. This residue is heated to separate the liquids from the solids.

Petrolatum occurs in a semi-solid (such as paraffin wax) or liquid form (paraffin oil) and is commercially available under a number of trade names, including Vaseline™. It ranges in colour from white to amber, and is practically odorless and tasteless.

Oils, fats and waxes in cosmetics

These ingredients are used in formulations as solubilisers, consistency factors, emollients and dispersing agents.

Solubilisers enable fragrances or essential oils to be incoporated into a solution.

Emollients lubricate and moisturise the skin, and provide the consumer with a pleasant skin feel. Natural emollients include cocoa butter and coconut oil.

Limitations of natural oils, fats and waxes

Natural derivatives can have the tendency to go rancid, oxidise or change consistency, which limits shelf-life and the quality of the final cosmetic product.

Crystallisation of fat, or 'bloom formation', is also a common problem. Blooming occurs when the solid fat material melts in the liquid phase and floats to the top of the surface, where it solidifies, leaving an undesirable appearance and texture.

Stability can also be an issue in the emulsifying stage. Many mixtures with natural products will split, so careful formulation is needed to ensure that this does not occur. 

Image courtesy of Self.

7th Jan 2019 Trulux

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