Petrolatum, commonly known as petroleum jelly, is a semi-solid mixture of hydrocarbons widely recognized for its moisturizing and protective qualities. This familiar substance, found in countless cosmetic and pharmaceutical products, was first commercialized in the 1870s by Robert Chesebrough. His initial product became a household name. The journey of this white, odorless material from a refinery byproduct to a highly refined consumer product involves a precise and complex manufacturing process.
The Raw Material Source
The manufacturing process for petrolatum begins within the crude oil refining industry, where it is a valuable derivative, not the primary target. Petrolatum is isolated from the heaviest fractions of crude oil, which is a complex mixture of hydrocarbons. These heavy hydrocarbon streams are the residues remaining after lighter, more volatile components, such as gasoline and kerosene, have been separated out.
The starting material is essentially a naturally occurring mixture of long-chain hydrocarbons trapped within the crude oil. This heavy, waxy component must be carefully extracted and purified.
Initial Distillation and Separation
The initial process to separate the petrolatum precursor from the heavy crude oil residue involves vacuum distillation. After atmospheric distillation removes lighter components, the remaining thick, viscous residue is heated again under reduced pressure. This vacuum environment allows the heavier fractions to vaporize and be collected at lower temperatures, preventing them from cracking.
This distillation step yields a heavy lubricating oil fraction containing wax. To isolate the semi-solid wax component, the material undergoes a process known as deoiling or dewaxing. Solvents are introduced to dissolve the liquid oil while causing the waxy solids to precipitate out. The resulting precipitate is a crude, yellowish substance referred to as “slack wax,” which serves as the direct precursor for petrolatum.
Advanced Purification for Cosmetic Grade
Slack wax requires advanced purification to become the pure, safe product used in cosmetic formulations. The primary goal is to remove impurities, especially potentially carcinogenic polycyclic aromatic hydrocarbons (PAHs), which are naturally present in unrefined petroleum derivatives. The raw material is treated to meet stringent international standards, such as those set by the United States Pharmacopeia (USP) or the European Pharmacopoeia (Ph. Eur.).
One common purification method is hydrogenation, where the slack wax is treated with hydrogen gas under high temperature and pressure. This process saturates the hydrocarbon bonds and is effective at removing sulfur, nitrogen, and other undesirable compounds, leading to an improved color and odor. An alternative method involves treating the material with sulfuric acid, followed by neutralization with sodium hydroxide and subsequent washing.
Following chemical treatment, the product is subjected to filtration through adsorbent materials like activated carbon, special clays, or silica gel. This filtration step is important for decolorization and deodorization, physically trapping residual trace contaminants and achieving the characteristic white appearance of cosmetic-grade petrolatum.
The Final Composition and Uses
The result of this refinement is a bland, semi-solid product defined as a mixture of highly refined, long-chain saturated hydrocarbons. The molecules in cosmetic-grade petrolatum are typically composed of carbon chains of C25 and higher. This structure, which includes both macro- and microcrystalline waxes, gives petrolatum its unique semi-solid texture and high melting point.
The primary function of this hydrocarbon blend is its occlusive property: it creates a physical, water-repellant barrier on the skin’s surface. This barrier prevents the natural loss of moisture from the skin, a process known as transepidermal water loss. This mechanism makes it effective for protecting compromised skin, sealing in hydration, and serving as a base for many medicinal ointments and creams.