Lip scrub: a sugar suspension that does not settle into a syrup at the bottom

A lip scrub formula with 45 to 55 percent sugar, the wax level that suspends it, particle size, jar filling at 45 to 50 C and the hygiene rules for a finger jar.

A lip scrub is the only anhydrous lip product that has to hold a heavy, water-soluble solid in place for a year without it moving. Get the base wrong and the sugar arrives at the bottom of the jar as a compacted cake under clear oil, or, if water has found its way in, as a syrup. This page gives the formula in weight percent, the reason the wax is there, and the two things that actually ruin a lip scrub: filling the jars warm, and putting a wet finger in them.

• Sugar 45 to 55% w/w
• Caster grade, 200 to 400 micron
• Fill at 45 to 50 C
• Anhydrous, no preservative
• 15 ml jar, spatula only

What a lip scrub has to do that a balm does not

A lip balm is one continuous phase: wax, butter and oil that melt together and set together. A lip scrub adds a second phase that never dissolves, never melts, is nearly twice the density of the liquid around it, and makes up roughly half the mass. That is a suspension problem, governed by different physics from the hardness problem that a tube balm formula solves.

The scrub also has a harsher life. It lives in an open jar, gets opened with a damp fingertip, and touches a mucous membrane that is wet by definition. Sucrose dissolves in water at roughly 2000 g per litre at 20 C, so one drip is enough to turn the surface of a lip scrub into syrup. And the abrasive has to suit lip skin, which is thin and has no useful sebaceous supply: sugar is friable and dissolves the moment it meets saliva, so the exfoliation stops on its own. A mineral grit does not stop.

The working formula

All figures are weight percent of the whole batch and total exactly 100. The gram columns are for a 60 g batch, which fills three 15 ml jars with a working margin, and a 200 g batch, which fills twelve.

Read the base separately from the sugar. Phases A and B come to 55% of the batch: about 9 parts beeswax, 33 parts shea and 57 parts liquid oil. On its own that is a soft, scoopable pot balm at around 9% wax, the consistency a tin balm wants. Adding 45% sugar does not make it stiffer in any useful sense; it makes it crowded.

For a scrubbier product, hold the base proportions and shift the split. At 55% sugar the base falls to 45% of the batch, so every base ingredient scales by 45/55: beeswax 4.1%, shea 14.7%, castor 4.1%, jojoba 6.5%, sunflower 15.0%, tocopherol 0.1%, flavour 0.5%. That totals 100. Past about 60% sugar the paste stops behaving as a suspension and starts behaving as wet sand, crumbling off the fingertip before it reaches the lip, and extra wax will not fix it.

Volume fractions explain that ceiling. Sucrose has a density near 1.59 g per cubic centimetre against roughly 0.91 for the set base, so 45% by weight is about 32% by volume and 55% is about 41%. Random packing of irregular crystals jams around 50 to 55% by volume, so at 41% the crowding is already doing some of the thickening. That is why a 55% scrub feels stiffer out of the jar despite holding proportionally less wax.

Yield stress, not viscosity, is what holds the sugar up

Most recipes claim thickness keeps the sugar suspended. Thickness is the wrong property. Stokes' law gives settling velocity as the density difference times gravity times diameter squared, over eighteen times the viscosity. Viscosity only slows settling: double it and the crystal takes twice as long. It still reaches the bottom.

Put numbers on it. A 300 micron sucrose crystal, a density difference of about 0.68 g per cubic centimetre against warm oil, and a base at 60 C behaving like an oil of roughly 15 mPa s gives a settling velocity near 2 mm per second. A 15 ml jar is about 30 mm deep. The sugar is on the bottom in under half a minute, while you are still holding the jug.

What stops a particle permanently is a yield stress: a stress below which the material does not flow at all. A crystal exerts a stress of roughly its density difference times gravity times its diameter, about 2 Pa for that same crystal. Numerical work on spheres held in yield-stress fluids puts the static criterion at a gravity yield parameter near 0.1 to 0.15, so the base needs a yield stress of only about 0.2 to 0.3 Pa to hold it indefinitely. Reported yield stresses for wax structured oils at 3 to 7% wax run from tens to hundreds of pascals depending on wax, oil and cooling rate. The margin is enormous. The background is on rheology and yield stress, and the wax network that produces it under oleogels and wax networks.

The conclusion is counterintuitive. 5% beeswax is not there to stop the sugar settling in the finished jar, because almost any set wax network does that with two orders of magnitude to spare. It is there so a workable yield stress already exists at 45 to 50 C, in the thirty seconds between adding the sugar and the paste setting. Sedimentation in a lip scrub is a filling fault, not a storage fault. It is also why a scrub left in a hot car comes back separated: above the network's softening range the yield stress collapses and Stokes' law takes over again.

Sugar grade, particle size and what each one feels like

Sugar is sold by sieve grade, not by a single crystal size, and the published ranges overlap. The differences on the lip are large.

Settling scales with the square of the diameter, so caster at 250 micron becomes granulated at 500 micron falling four times faster, which shrinks the filling window rather than defeating a set base. Brown sugar is a separate warning: the soft brown grades are white sugar coated in a molasses film carrying a few percent free water, which is in the jar from day one, dissolving sugar at every surface it touches. If you want the colour, use a lip-legal tint instead.

Method

1. Dry the jars completely. Wash, rinse, dry in a warm oven, cool covered. A rinsed jar that looks dry still holds droplets in the thread, and every one is liquid water: see workshop hygiene.
2. Weigh phase A into one jug. Beeswax, shea, castor, jojoba and sunflower, tared between additions. Phase B into a small dish, the sugar into a bowl.
3. Melt at 75 to 80 C. Stand the jug in simmering water until the liquid is optically clear. Shea that has not fully melted crystallises into grit later, which you will blame on the sugar: see grainy shea butter.
4. Cool below 60 C, add phase B. Off the heat, stirring, add tocopherol and flavour once the reading is under 60 C (140 F).
5. Keep stirring down to 45 to 50 C. Judge by eye as well as thermometer: the base turns from clear amber to opaque, and a spatula trail closes slowly rather than instantly. That trail is the yield stress appearing.
6. Fold the sugar in, in two halves. Fold, do not beat. Beating whips air into an already thick paste, and the bubbles float sugar upward as it sets.
7. Spoon into jars. Spoon rather than pour, and tap the jar twice on a folded cloth to level it. Do not press the surface down, which compacts the sugar and squeezes oil to the top.
8. Cure 24 hours uncapped at room temperature in a dry room, then cap and label. Judge the texture at 24 hours, not at 20 minutes.

The window matters at both ends. Above about 55 C the base is thin enough for the sugar to sink before it sets; below about 40 C it is too stiff to take the sugar evenly, so the sugar stays where the spatula left it and traps air on the way in. Filling windows generally are at pour temperatures, though a scrub is filled cooler than any pourable balm.

Water is the entire problem

An anhydrous balm needs no preservative because microbes cannot grow without free water, and the thresholds behind that are at do balms need preservatives. A scrub qualifies on the same grounds with one difference: it holds 45 to 55% of a soluble solid that dissolves into any water it meets. Concentrated sugar syrup is itself microbiologically hostile. The dilute film left by a drip of tap water is not.

Three routes let water in, and all three are ordinary. The first is a wet finger: a scrub is used on wet lips, often straight after washing, and the finger goes back into the jar, depositing water, skin cells and mouth flora in a nutrient-rich matrix. Use a small spatula, or decant a week's worth into a second jar; the alternative is at mould in balm. The second is the room: oils are mildly hygroscopic and equilibrate toward the humidity around them, so a jar left open during showers takes up water at the surface. Store it in a bedroom drawer.

The third is deliberate, and it is the reason most craft lip scrubs spoil: adding honey, aloe, fruit puree, glycerin or milk because a recipe said so. Honey in balms is the usual culprit. Honey is typically 15 to 20% water with a water activity around 0.5 to 0.6, low enough to resist most bacteria but well within range for the osmophilic yeasts that spoil honey itself. In a scrub it does not disperse. It forms discrete aqueous droplets in an oil continuum, each one an undefended growth site sitting against a limitless supply of dissolved sugar. See water contamination in balm for what follows.

Safe to swallow and safe on skin are two separate tests

A lip scrub is a cosmetic, not a food: the EU and UK under Regulation (EC) No 1223/2009, the US under the Federal Food, Drug, and Cosmetic Act. But the lip is a mucous membrane and a real proportion of what you apply is swallowed, so a scrub has to clear both bars. Food-grade alone is not enough, and cosmetic-grade alone is not enough either.

US colour additive law shows the first half clearly. 21 CFR 70.3 defines an externally applied cosmetic as one applied only to external parts of the body, explicitly not including the lips or any surface covered by mucous membrane. A colour additive listed for external use only is therefore illegal in a lip product, however natural it looks in a catalogue. The EU handles the same question through Annex IV of 1223/2009, whose field-of-application column restricts some colourants to rinse-off products or excludes them from mucous membranes. Work from the annex or the CFR listing, not marketing copy: see colourants and tints.

Flavour runs the test in the opposite direction. A food flavouring is safe to swallow by construction but has not been assessed for repeated skin contact, and may carry fragrance allergens that IFRA restricts well below the level a food use implies. A cosmetic flavour sold as lip-safe has been assessed for the skin side. Keep total flavour at or below about 0.5 to 1% and read lip balm flavour and sweeteners before substituting. Menthol and camphor have their own limits, at menthol and camphor safety limits, and both are easy to overdose in a product rubbed hard into thin skin.

One labelling consequence: on an ingredient list the sugar is Sucrose, not "sugar", and it sits at or near the top because it is the largest single component by weight.

Other abrasives, and how the numbers change

• Best alternative

  Jojoba beads

  Hydrogenated jojoba esters, sold in graded spheres from about 150 to 600 micron. Their density of roughly 0.86 to 0.90 g per cubic centimetre is at or below the base, so they do not sink and may cream slowly upward. That removes the suspension problem and lets you drop beeswax to 3 to 4%. Use 15 to 25% by weight. They do not dissolve, so the exfoliation does not stop by itself, and they cost several times what sugar does.

• Workable

  Ground rice or rice flour

  Irregular particles around 100 to 400 micron, harder than they sound and dry-feeling on the lip. Use 20 to 30% with 3 to 5 percentage points more liquid oil, because starch absorbs oil and the paste reads stiffer at the same solids loading. The catch is that it is a starch: if water gets in it is a growth substrate as well as a wetting agent. See starches and silica.

• Avoid

  Salt and mineral grits

  Fine sea salt dissolves faster than sucrose, stings split skin, and pulls water out of humid air on its own. Pumice, walnut shell, bamboo powder and cosmetic silicas are too aggressive for lip skin at any size that would actually abrade, and unlike sugar they do not vanish when they meet saliva, so the rubbing continues for as long as you keep going.

What goes wrong

Two notes on materials. Shea butter at 18% does the cushioning, but unrefined shea carries a taste some dislike in a product that ends up in the mouth, so use refined here. The tocopherol at 0.1% preserves nothing; it slows oxidation of the oil phase, the only spoilage route a correctly made scrub has.

When a lip scrub is the wrong product

The honest limit: a scrub removes flakes of stratum corneum that were already detaching. There is no good evidence that abrading the vermilion border speeds the recovery of chapped lips, and a clear mechanism by which it does the opposite, since the barrier there is thin and already compromised when lips are chapped. If the skin is split or bleeding, stop scrubbing, and see cracked corners of the mouth, which is often not a dryness problem at all. If lips feel worse the more product goes on them, does lip balm dry your lips matters more than any scrub formula.

The decision rule: intact skin only, once or twice a week at most, ten seconds of light pressure, followed by an occlusive balm, which is the part that actually reduces water loss. Make the 60 g batch, keep one jar, and check it at four weeks for a wet layer at the bottom. That single observation is worth more than any adjustment to the percentages.

Reviewed and updated 6 September 2026. Spotted an error? Tell us and we will fix and log it.