How Petroleum Jelly Is Made: From Crude Oil to Final Product

Petroleum jelly starts as a waxy residue that accumulates on oil-drilling equipment, and it becomes the smooth, translucent product on store shelves through a series of distillation, dewaxing, and purification steps that strip away color, odor, and potentially harmful impurities. The journey from crude oil to a jar of pharmaceutical-grade petrolatum involves surprisingly aggressive chemistry, and the final product’s usefulness depends almost entirely on how well that purification is done.

The Raw Material Hiding Inside Crude Oil

Crude oil is not a single substance. It is a stew of thousands of different hydrocarbon molecules ranging from light gases to heavy, tar-like compounds. Petroleum jelly belongs to the heavier end of that spectrum. The specific hydrocarbons that make up petrolatum are a blend of long-chain molecules, described technically as liquid and semisolid mixtures of hydrocarbons obtained from petroleum.¹ These include both straight-chain paraffins (think of them as molecular rods) and branched or cyclic hydrocarbons (more like molecular tangles). The exact proportions vary depending on the crude oil source, which is one reason petrolatum from different suppliers does not always behave identically.

The story of how anyone thought to turn this oily gunk into a skin product traces back to the mid-1800s, when oil workers in Pennsylvania noticed a thick, waxy buildup on their drilling rigs. They called it “rod wax” and, despite its unappetizing appearance, found that smearing it on cuts and burns seemed to help them heal. Robert Chesebrough, a chemist, spent years figuring out how to purify that rod wax into something clean enough to sell. The product he eventually patented became Vaseline, and the basic manufacturing logic he pioneered still underpins modern production, though the chemistry has gotten considerably more sophisticated.

Distillation Separates the Starting Fractions

The first major step happens at a petroleum refinery, where crude oil is heated in a distillation column. Different hydrocarbon fractions boil off at different temperatures: light gases rise to the top, gasoline and kerosene condense in the middle, and heavy residues collect near the bottom. The fraction relevant to petroleum jelly sits among the heavier cuts, often emerging alongside lubricant base oils. This heavy fraction is a dark, smelly, impure mixture that looks nothing like the translucent jelly you would recognize.

Vacuum distillation is often used for these heavy fractions because they would crack, or break apart chemically, if heated to their normal boiling points at atmospheric pressure. By reducing the pressure inside the column, refiners can separate these heavy molecules at lower temperatures without destroying them. What comes out is a waxy, oil-rich intermediate that still needs extensive processing.

Dewaxing and Deoiling

The heavy distillate contains both liquid oil and solid wax components. For lubricant production, the wax is a nuisance because it thickens the oil at low temperatures. But for petroleum jelly production, the wax is the prize. These waxes are mainly derived from paraffinic crudes and must be separated from lubricant base oils through a dewaxing process.²

Dewaxing typically involves chilling the heavy oil fraction, sometimes after diluting it with a solvent like methyl ethyl ketone or toluene. As the mixture cools, wax crystals form and can be filtered out. The resulting “slack wax” is a crude, oily solid. It then goes through a deoiling step, where gentle heating or additional solvent washing separates the residual oil from the wax crystals. The degree of deoiling matters: petroleum jelly is not pure wax, nor is it pure oil. It is a carefully controlled blend of the two, and its consistency depends on getting the oil-to-wax ratio right.

Different wax types emerge from this process. Macrocrystalline wax, made of long, straight-chain paraffins, forms large crystals. Microcrystalline wax, made of more branched and cyclic molecules, forms tiny crystals. Petroleum jelly typically uses a blend of both, because the microcrystalline fraction helps create the smooth, spreadable texture consumers expect, while the macrocrystalline fraction provides structural firmness.

Purification Turns Dark Wax Into a Clean Product

At this stage, the wax blend is still far from pharmaceutical grade. It contains colored compounds, sulfur-bearing molecules, aromatic hydrocarbons, and other impurities that need to be removed. This is where the manufacturing process diverges depending on the intended end use. Industrial-grade petrolatum gets lighter treatment, while cosmetic and medicinal grades undergo aggressive purification.

Two key purification methods are sulphonation and hydrogenation. Research on producing medicinal petroleum jelly from local waxes has shown that optimizing the conditions for these two processes can yield macro- and microcrystalline waxes that meet medicinal specifications.² Sulphonation uses sulfuric acid to react with and remove aromatic and unsaturated compounds, which are the molecules most likely to cause skin irritation or carry carcinogenic potential. Hydrogenation, the same basic reaction used to turn vegetable oil into margarine, forces hydrogen gas through the wax in the presence of a metal catalyst. This saturates any remaining double bonds in the hydrocarbon chains, making the product more chemically stable and less reactive.

After these chemical treatments, the petrolatum typically goes through adsorption filtration, where it is passed through beds of activated clay or similar materials. The clay grabs onto remaining pigments, odor-causing molecules, and polar impurities. The result is a dramatic color change, from a dark amber or brown mass to the pale, nearly white jelly used in skin-care products. A final filtration step removes any clay particles, and the purified petrolatum is heated, blended to a target consistency, and poured into containers.

What Petroleum Jelly Actually Looks Like at the Molecular Level

The finished product is not a simple solid or a simple liquid. It exists in a state scientists call semi-crystalline: tiny crystalline domains are suspended in a continuous matrix of liquid oil. Research using X-ray scattering techniques has shown that petrolatum from various commercial sources contains crystalline fractions ranging from roughly 10% to 17%, with the crystalline domains arranged in an orderly layered structure with a repeating spacing of about 9 to 10 nanometers.³ Think of it as a microscopic scaffolding of tiny wax platelets holding pools of liquid oil in place, like a sponge holding water.

This structure is what gives petroleum jelly its distinctive feel and behavior. When you scoop it from the jar, it holds its shape. But when you rub it between your fingers or spread it on skin, it softens and flows. This happens because the crystalline network breaks apart under mechanical pressure, a behavior described as shear-thinning. The disruption of the crystalline network under shear deformation is what allows petrolatum to spread easily despite feeling semi-solid at rest.⁴ Once you stop rubbing, the network slowly re-forms, which is why a thin film of petroleum jelly stays put on skin rather than running off.

The variation in crystallinity between different petrolatum sources is worth noting, because it affects how the product performs. A batch with higher crystallinity feels firmer and more waxy. A batch with lower crystallinity is softer and oilier. For something like an ophthalmic ointment, where consistency needs to be tightly controlled so the product spreads evenly across the eye without clumping, these differences matter quite a bit. Manufacturers blend different wax fractions and oil ratios to hit their target specifications, and the same brand can source petrolatum from different refineries, introducing subtle batch-to-batch variation.

How It Behaves on Skin

The reason petroleum jelly works so well as a moisturizer has less to do with adding moisture and more to do with preventing its loss. When applied to skin, petroleum jelly creates an oily layer that sharply reduces transepidermal water loss, the slow evaporation of water from deeper skin layers through the surface.⁵ This occlusive effect is well documented on both healthy and damaged skin.

For a long time, people assumed petroleum jelly just sat on top of the skin like a plastic wrap, passively blocking evaporation. That picture turned out to be incomplete. Research has found that petrolatum actually permeates into the spaces between skin cells at all levels of the outer skin layer, replacing the natural lipid structures that normally fill those gaps. Rather than forming an impermeable barrier on the surface, it integrates into the skin’s existing architecture, and it accelerates rather than impedes the skin’s own barrier-repair processes.⁶ This finding helped explain something clinicians had observed for decades: wounds treated with petroleum jelly heal well, even though a truly impermeable barrier would theoretically trap bacteria and slow recovery.

The oily layer also has emollient properties, softening dry or rough skin by filling in microscopic cracks and irregularities. Research has confirmed that oily vehicles like petrolatum can help restore the outer skin layer and stimulate the skin’s own production of the lipids it uses for waterproofing.⁵ This dual role, as both a passive shield and an active participant in skin repair, is unusual among moisturizing ingredients and helps explain why dermatologists still recommend it so heavily despite the availability of more cosmetically elegant products.

The Greasiness Problem

If petroleum jelly is so effective, why does the cosmetics industry spend so much effort formulating alternatives? The answer is sensory. Petrolatum feels greasy. Research into how consumers perceive cosmetic products during application has identified greasiness as a characteristic sensation caused by petrolatum and similar hydrogenated oils, one that formulators sometimes try to minimize.⁷ That heavy, slick feeling is a direct consequence of the molecular structure: long hydrocarbon chains do not absorb quickly into the skin the way lighter oils or water-based formulations do.

Many modern moisturizers use petrolatum as a base but combine it with emulsifiers, water, and other ingredients to create lighter-feeling creams and lotions. In these formulations, the petrolatum still does its occlusive job, but the overall texture is less objectionable to consumers. Pure petrolatum remains the gold standard for maximum occlusion, though, which is why it is still the go-to for situations where performance matters more than elegance: post-surgical wound care, severe dry skin, cracked lips in winter, and protecting tattoos during healing.

Safety and the Polycyclic Aromatic Hydrocarbon Question

The biggest concern people raise about petroleum jelly relates to its origin. If it comes from crude oil, does it carry the cancer-causing compounds that crude oil is known to contain? The answer hinges entirely on the purification process.

Crude oil and its less-refined derivatives do contain polycyclic aromatic hydrocarbons, or PAHs, some of which are known carcinogens. Early toxicology studies examined 36 samples of petroleum wax and found identifiable PAHs in eight of them, including compounds like chrysene and fluoranthene, though the highest concentration found was only 0.64 parts per million. Those studies concluded that no carcinogenic or other toxic hazard had been demonstrated in petroleum waxes used in food or food-packaging applications.⁸ The levels were simply too low to pose a measurable risk.

Modern analytical chemistry can detect PAHs at far lower concentrations than older methods could, and testing of contemporary cosmetic products has confirmed that properly refined petrolatum contains only trace amounts. In one study that screened a range of cosmetic raw materials and finished products, petrolatum samples showed detectable levels of only a few individual PAHs, with concentrations around 0.1 to 0.4 milligrams per kilogram. None of the petrolatum samples contained the two PAHs considered most carcinogenic. When compared against the most stringent reference limits available at the time, nearly all samples fell well within acceptable ranges.⁹

The practical takeaway is that the distinction between “petroleum-derived” and “unsafe” collapses under scrutiny for properly refined products. Pharmaceutical-grade and USP-grade white petrolatum has undergone enough hydrogenation, acid treatment, and adsorption filtering to remove the problematic aromatic compounds. The residual traces are at levels comparable to those found in many plant-derived oils, which also contain PAHs from environmental exposure. The real risk would come from using unrefined or poorly refined petroleum products on skin, something that does happen in some markets where quality control is less rigorous. If a petrolatum product meets USP or European Pharmacopoeia standards, its PAH content has been driven down to negligible levels.

Why Different Brands Feel Different

Not all petroleum jelly is created equal, and the reason goes back to the semi-crystalline structure described earlier. The crystallinity of petrolatum from various commercial sources has been measured at anywhere from about 10% to 17%, with corresponding differences in lamellar spacing.³ These might sound like tiny differences, but they translate into noticeable variation in firmness, spreadability, and how the product feels on skin.

Manufacturers control texture by adjusting the ratio of microcrystalline to macrocrystalline wax, by varying the oil content retained after deoiling, and by choosing different blending temperatures. A product blended at a higher temperature and cooled quickly will have a different crystal structure than one cooled slowly. Even the type of crude oil used as a starting material matters, because crudes from different geological formations produce waxes with different chain-length distributions.

Thermal analysis of wax-based personal care formulations has shown that blending petrolatum with paraffin wax changes the decomposition profile, producing a narrower and faster thermal breakdown compared to pure petrolatum.¹⁰ This kind of testing helps formulators predict how a product will behave in storage and during use. A petrolatum blend that decomposes at a different rate or temperature might soften unpredictably in a hot warehouse, for example, or develop an off-putting texture after sitting on a shelf for a year.

For everyday consumer use, these differences are mostly cosmetic preferences rather than functional ones. A firmer petroleum jelly and a softer one will both reduce water loss from skin effectively. But for pharmaceutical applications like ophthalmic ointments or drug-delivery bases, the variation can affect how evenly a medication is dispersed through the jelly and how consistently it releases onto tissue. That is why pharmaceutical manufacturers test incoming petrolatum batches for crystallinity, viscosity, and melting behavior before accepting them.

Plant-Based Alternatives and What They Change

Growing consumer interest in avoiding petroleum-derived ingredients has pushed the cosmetics and personal care industry to develop plant-based alternatives to petrolatum. These products, often based on combinations of plant waxes like candelilla, carnauba, or rice bran wax blended with vegetable oils, aim to replicate petrolatum’s semi-solid texture and occlusive properties without the crude-oil origin story.

The challenge is that petrolatum’s performance comes from its specific molecular architecture, that network of hydrocarbon crystals holding liquid oil in a stable matrix. Plant waxes have different crystal structures, different melting points, and different interactions with skin lipids. Some plant-based alternatives come close in terms of occlusivity, but achieving the exact same spreadability, stability, and shelf life requires careful formulation work. The shear-thinning behavior that makes petrolatum so easy to apply is a direct consequence of its particular crystalline network.⁴ Replicating that behavior with a completely different set of molecules is not straightforward.

Plant-based alternatives also carry their own impurity concerns. PAHs exist in the environment, and plant waxes can absorb them from soil, air, and processing equipment. The assumption that “natural” automatically means “purer” does not hold up under chemical analysis. What matters for safety is the final product’s contaminant profile, not whether its carbon atoms were once part of an ancient marine organism or a recently living plant. For consumers who prefer to avoid petroleum products for environmental or ethical reasons, plant-based options are a legitimate choice, but the safety argument for switching is weaker than marketing materials tend to suggest.