An eyeliner is three products sharing a category name. A liquid liner is a thin film-forming solution delivered by a nib, a gel liner is a structured thixotropic paste delivered by a brush, and a pencil is a solid wax stick delivered by abrasion. They are made on different equipment, tested against different failure modes and priced against different cost drivers, and the only thing they have in common is the line they draw.
This article compares the three formats on the variables that decide how they behave: what the line is made of, how the applicator sets the width, how a long-wear claim is built and what it costs the customer at removal, how pigment loading differs across formats, where the microbiological risk sits in each, and what each format needs in the brief before development starts.
Three formats, three different physics
A liquid liner sets by evaporation. The applied line is a solution or a dispersion in a volatile carrier, and the film forms as the carrier leaves. That means the film is deposited almost intact, the line is thin, and the precision depends on the nib geometry and on the flow through it.
A gel liner sets by cooling and by structure recovery. The paste is thick at rest, thins under the shear of the brush, and recovers its structure when the shear stops. The film retains some of the oil and wax, so it stays slightly pliable and reads as a softer edge.
A pencil sets by mechanical transfer at skin temperature. The stick is abraded against the lid, and the heat and friction of the application soften it just enough to deposit a layer. The film is the thickest of the three formats and the softest, and that is the source both of its blendability and of its smudge tendency.
The consequence is that a performance target is not transferable between formats. A brand that asks for the wear of a liquid liner in the texture of a pencil is asking for a different product, and the conversation is more productive when the trade-off is named at the start.
Liquid eyeliner: water-based, film former and the pen
A water-based liquid liner is mostly water, a film former at ten to twenty percent, pigment at eight to fifteen percent and a small amount of humectant and preservative. The film former is usually an acrylate copolymer or a vinylpyrrolidone and vinyl acetate copolymer, chosen for water resistance and for flexibility so that the line does not crack as the lid moves.
An anhydrous liquid liner replaces the water with a volatile silicone or a light isoparaffin and uses a silicone resin as the film former. The anhydrous version usually sets faster, resists water better and is harder to remove, and it is the version most often chosen for a long-wear positioning.
The pen is a metering device and a failure point. A felt nib draws product from a reservoir by capillary action, and the flow depends on the formula's viscosity and on the pigment particle size. A pigment that is not milled finely enough will clog the nib over the life of the product, and the user experiences that as a liner that stops performing before the reservoir is empty.
Viscosity in a water-based liner usually sits between a few hundred and a couple of thousand centipoise, and it is a narrow window. Too thin and the line bleeds into the fine lines around the eye; too thick and the nib starves. The window is also temperature sensitive, which matters for a product sold in a range of climates.
Gel and cream liners: wax, oil and the pot or the pencil
A gel liner is a wax and oil structure holding a high pigment load, with a rheology modifier providing the thixotropic behaviour that lets a brush pick up the paste and then shape a line. The wax blend is usually softer than a pencil's, because the product is delivered by a brush rather than by abrasion, and a hard wax would resist pick-up.
The pigment load in a gel liner is typically higher than in a liquid one, because the film is thicker and the carrier does not evaporate away. A load of fifteen to twenty-five percent is normal, and it is the reason a gel liner reads as a saturated black with a single pass while a liquid liner may need two.
The pot raises two problems that a pen does not have. The first is exposure: a wide-mouth pot is re-opened repeatedly and the surface is in contact with a brush that has been on the skin, so the microbiological challenge is higher. The second is drying, because a pot has a large surface area relative to its volume and an imperfect seal will thicken the surface layer.
Gel liners are also sold in pencil form, where the same paste is extruded into a barrel. That format gets the pick-up and the soft edge of the gel with the convenience of a pencil, and it inherits the pencil's need for a stable core that does not sweat oil in a warm room.
Pencil and kohl: the wax-to-oil ratio and the pay-off
A pencil core is a wax blend with oils and pigments. The wax load sits around thirty to forty percent and the oil load around twenty-five to thirty-five percent, and the balance between them, together with the wax types chosen, sets the hardness that the user feels as pay-off.
Harder cores lay down less colour per stroke, hold a sharper point and are easier to control. Softer cores deposit more colour and blend more readily, and they also wear down faster and are more prone to breaking in the barrel. A kohl is at the soft end, formulated to deposit heavily and to be smudged, and it is expected to be consumed quickly.
The oil phase matters as much as the wax. A core built on oils that stay liquid at room temperature will soften in a warm environment and can sweat, leaving a film on the barrel and a core that bends under pressure. A core built on oils that are too heavy will drag on the lid and deposit unevenly.
The barrel is part of the specification. A wood-cased pencil requires a core diameter matched to the barrel and a wood that sharpens cleanly without splitting the core; a retractable format requires a mechanism that advances the core without crushing it, and the mechanism sets a limit on how soft the core can be.
Pigment loading and the depth of black across formats
Black iron oxide is the standard colourant across all three formats. The load differs because the film differs: a liquid liner carries the least pigment because the film is thin and the carrier leaves, a gel carries more, and a pencil carries the most because the deposited layer is the thickest.
Coloured liners behave differently from black ones. A blue or green pigment has less covering power per unit weight, so the load rises and the effect on the structure rises with it. A coloured pencil needs a harder wax blend to compensate for the softer pigment load, and a coloured gel needs a rheology adjustment to hold the higher solids.
Where a market also permits carbon black in defined uses, the two blacks do not read the same. Carbon black is more neutral and stronger at a lower load, and iron oxide black carries a warmer undertone. The choice is usually fixed by the permitted status in each market rather than by preference, which is why the market list belongs in the first brief rather than the last.
Dispersion quality again decides how much of the load is doing work. A pigment milled to a fine and narrow particle size develops more colour and clogs a nib less; a coarse dispersion needs a higher load to read as black and produces a line that looks grey at the edges.
Precision, the applicator and how line width is set
Line width is set by the applicator, not by the formula, in every format where the applicator touches the skin. A felt nib has a fixed contact area and produces a consistent width until it clogs; a brush allows a range of widths and depends on the user; a pencil produces a width determined by the point and by the pressure.
The formula sets the sharpness of the edge. A thin, fast-setting liquid produces a crisp edge with almost no bleed. A gel produces a slightly softer edge because it stays mobile for a moment after application. A pencil produces the softest edge, and that softness is the property that makes it blendable.
The interaction matters when a brand changes one and not the other. A sharper nib in the same liquid produces a thinner line with the same edge sharpness, which is usually acceptable; a thinner formula in the same nib produces a line that bleeds, which is not. Applicator changes should be validated against the formula before the artwork is finalised.
Long-wear, water resistance and the removal problem
Long-wear liners achieve their wear through film formers and water-resistant resins, and the same components that keep the line on the lid keep it resistant to a simple cleanser. The user then needs an oil-based remover, and a product that does not say so will generate complaints about difficulty of removal rather than about performance.
Gels and pencils reach a similar wear result by a different route. A gel's film is thicker and contains wax, which resists water and sebum better than a thin water-based film, though it transfers more readily on oily lids. A pencil's wear depends on the wax blend holding to the skin, and the most common failure is transfer to the crease rather than disappearance of the line.
Support for a wear claim should be a test result rather than a description. The usual in-vitro approach applies a defined mechanical and moisture challenge against a control and reports the change in the line. The conditions have to be agreed with the wording, because a claim supported by one protocol may not survive a stricter one.
Water resistance and smudge resistance are again separate properties. A line can resist a water splash and still transfer under a fold of the lid, and a brand that tests only for water will be surprised by the complaint it receives.
Microbiological risk by format
The water-based liquid liner carries the highest risk, because it is a wet product applied close to the eye and delivered through a nib that is in contact with the skin. The preservative system has to be validated in the finished formula against a defined panel of organisms, and the film former and pigment surface can reduce the available concentration of some preservatives.
The gel liner carries a lower water risk, since many gel formulas are substantially anhydrous, but a higher exposure risk, because the pot is open during use and the brush returns to it. Where the formula does contain water, the preservative requirement returns in full.
The pencil carries the lowest microbiological risk of the three, because it is a solid with little available water. Its risk sits in the wood and the barrel rather than in the bulk, and the specification should address the barrel surface where the product is applied near the eye.
Across all three formats the period-after-opening marking belongs in the specification, and it should reflect the format rather than a category norm. A water-based pen and an anhydrous gel do not have the same in-use life, and the marking should say what the testing supports.
Eyeliner variables at a glance
| Variable | Liquid | Gel or cream | Pencil |
|---|---|---|---|
| Setting mechanism | Carrier evaporation | Cooling and structure recovery | Transfer at skin temperature |
| Film former | Ten to twenty percent | Low, wax carries the film | None, wax is the film |
| Wax load | None or minimal | Moderate, brush pick-up | Thirty to forty percent |
| Pigment load | Eight to fifteen percent | Fifteen to twenty-five percent | Fifteen to twenty-five percent |
| Edge quality | Crisp | Slightly soft | Softest, blendable |
| Microbial risk | Highest, wet format | Exposure risk at the pot | Lowest, solid format |
| Removal | Often needs an oil remover | Soap and water usually enough | Soap and water usually enough |
| Main failure mode | Nib clogging and bleed | Drying at the surface | Sweating and core breakage |
What to put in the brief
- The format, since liquid, gel and pencil differ in failure mode as well as in feel.
- The line width range the user should be able to achieve with the applicator.
- The wear expectation, stated as a test protocol rather than as a number of hours.
- The water-resistance expectation, kept separate from the smudge expectation.
- The removal route the brand is prepared to tell the customer about.
- The pack, because a pot and a pen and a barrel carry different risk profiles.
- The markets of sale, so the permitted black and the coloured pigments are settled first.
- The period-after-opening marking the brand intends to declare.
Where our capability fits
We develop eyeliner format by format rather than by category, because the film physics differ. A liquid project is built around the film former and the nib; a gel project around the wax and oil structure and the rheology; a pencil project around the wax-to-oil ratio and the barrel. In each case the applicator and the pack are in the specification before the wear testing starts.
We work with brands on private label (your brand on a proven base), OEM/ODM contract manufacturing, and full custom formula development — whichever matches where your brand is today. Our lines include a solid essence stick format, a long-lasting waterproof foundation and a plant-based purifying cleansing oil, all of which rest on the same wax structure, film former and removal side thinking that an eyeliner programme needs.
Tell us the format and the applicator you have in mind, and we will map the film system, the pigment load and the wear test against your own brief. Start at our inquiry page, email capsulebiotech@163.com, or message the right team on WhatsApp: Capsule Series (capsules only) +86 158-7655-5319, Cosmetics Series (serum, hair care, body care, fragrance) +86 158-7655-5319. Pack-level compatibility work is covered in our guide to packaging compatibility testing, and moulds and tooling in our article on custom shapes, sticks and compacts.
General manufacturing information, not regulatory or legal advice. Permitted colourants, wear claim support and labelling requirements vary by market and by product.