Body Scrub and Exfoliating Body Care: Formulation and Fill
Body scrubs look like the easiest product to make and are among the hardest to ship. The product is a suspension of particles in a base, and suspensions separate. Understanding the relationship between particle size, base viscosity and package geometry explains why some scrubs arrive as a smooth cream and others arrive as a jar of liquid with a layer of grit at the bottom.
Choosing the Exfoliant
The particle does three things: it provides the mechanical action, it contributes to the perceived value, and it sets the formulation constraints.
- Sugar. Water soluble, which means it dissolves during use and the scrub becomes progressively gentler. Dissolves in storage too if any free water is present, which is why sugar scrubs are almost always anhydrous or very low water. Particle sizes usually run from 200 to 800 microns.
- Salt. Sharper and more abrasive, and it dissolves in water. Sea salt scrubs are popular and also the most prone to causing stinging on broken skin. Salt also raises the ionic strength, which destabilises many emulsifier systems.
- Ground nutshells and seeds. Insoluble, sharper, and a persistent environmental talking point since they do not biodegrade quickly. Walnut shell and apricot kernel are common. Particle size is more variable, which makes sensory consistency harder.
- Beads and synthetic particles. Uniform and predictable, but plastic microbeads are banned in many markets and biodegradable alternatives cost more. Where a uniform look is essential, a plant wax bead is the usual answer.
- Pumice and volcanic minerals. Very abrasive, used at low percentages for foot and heel products rather than body.
Particle size distribution matters more than the average size quoted. A supplier who specifies only a mesh range can still deliver a batch with a wide spread, which produces an inconsistent scrub. Ask for the distribution, not just the range.
The Base Decides Whether the Particles Stay Suspended
A suspension settles when the density difference between the particle and the base is large and the base viscosity at low shear is low. The formulation levers are:
- Yield stress. A base with a genuine yield stress holds particles indefinitely. This is the property to specify, not the viscosity measured at a single shear rate. A thick product that pours easily can still have almost no yield stress.
- Rheology modifier choice. Clay, a synthetic suspending agent or a structuring wax each give a different feel. Clay is cheap and imparts a matte look but can be drying. Synthetic suspending agents give a cleaner feel at higher cost.
- Particle density. Salt is denser than sugar and both are denser than a wax bead, so the same base will hold wax beads and fail to hold salt. Sugar in an oil base is the easiest combination to keep in suspension because it is the closest in density and it dissolves slowly.
- Temperature history. A product that is stable at 25 degrees Celsius can settle after a summer in a warehouse at 40 degrees Celsius, because viscosity falls. Test with a temperature cycling programme, not a single condition.
Anhydrous, Emulsified or Water Based
Three families cover nearly all products. Anhydrous sugar and oil scrubs are the simplest to make and to preserve, since with no water phase there is no microbiological risk in the normal sense. They are also messy in the shower and leave oil residue, which some consumers dislike.
Emulsified scrubs contain a small water phase and an emulsifier so that the product turns milky on contact with water. This is the most popular consumer format and the most difficult to formulate, because the salt or sugar can break the emulsion and the water content means a preservation system and a challenge test are required.
Water based gel scrubs use a surfactant base with suspended particles and are the easiest to rinse. Their limitation is particle suspension, since a water thin gel will not hold salt.
Filling and Packing Problems
Scrubs are difficult to fill because the particles abrade the filling equipment and the product does not flow predictably. Three issues recur:
- Particle damage during pumping. A progressive cavity or peristaltic pump handles particles more gently than a piston filler. Damaged particles produce fines, which change the sensory experience and can make the scrub feel like it is not scrubbing.
- Settling in the hopper. A large hopper with a long residence time allows the particles to separate before filling, so early jars and late jars of the same batch differ. Recirculation or a smaller hopper with continuous feed solves it.
- Pack geometry. A narrow necked bottle will not dispense a large particle scrub. Wide mouth jars are the default for good reason, and a tube with a large orifice is the practical alternative for a product meant to be squeezed rather than spooned.
Weight tolerance is also looser than for a liquid, because the fill is by volume of a heterogeneous material. Set the declaration with the tolerance and the settling behaviour in mind rather than assuming the accuracy achievable on a lotion.
Claims and Sensitivities
Exfoliates, smooths, polishes, leaves skin feeling soft. Those are appearance and feel claims and they are appropriate. Claims about removing cellulite, detoxifying the skin, or drawing out impurities are either unsupportable or classified as a therapeutic claim in most markets and should be avoided.
One genuine safety point: a scrub should not be positioned for use on freshly shaved skin or on irritated areas, and the label is a reasonable place to say so. Salt and nutshell scrubs in particular generate stinging complaints, and a simple usage caution reduces returns at no cost.
Scrubs Built to Survive Shipping
OEM COSMETICS ODM produces sugar, salt, coffee and mineral scrubs in anhydrous, emulsified and gel formats on ISO 22716 and GMP certified lines, with suspension stability cycling, particle size control and pack dispensing tests included in development. Send us the format and the sensory target and we will confirm the base that holds it.
Talk to our team: WhatsApp +86 18709713948 · Email adon@oemcosmeticsodm.com · Website www.oemcosmeticsodm.com