What is a colloid mill?
A colloid mill (also called a colloidal mill) is a machine that reduces the particle size of solids dispersed in a liquid, or emulsifies one liquid into another, using high shear.
It has two main parts: a rotor and a stator. Both have highly polished surfaces that run very close to each other. The rotor turns at high speed while the stator stays still, and the product is sheared in the gap between them.
The name comes from what it makes. A colloid is a mixture in which fine particles or droplets are spread through a continuous medium. An emulsion is a colloid in which both phases are liquids. A colloid mill brings the particles or droplets down to a few micrometres and spreads them evenly, so the product is uniform and stays stable.
Colloid mill working principle
How a colloid mill works, step by step:
- Feed. The liquid, carrying the solids or droplets to be reduced, flows into the mill and through the gap between the rotor and the stator.
- High-speed rotor, fixed stator. The rotor turns at high speed next to the stationary stator. Their polished surfaces are very close together.
- Shear. The close clearance and fast rotation create intense mechanical and hydraulic shear in the gap, together with impact and compression forces.
- Size reduction. Particles break down and droplets split, and both are dispersed evenly through the liquid.
- Discharge. The finished product leaves the mill and is collected, for example in a storage tank.
On a multi-stage mill, the product passes through several rotor-stator stages, so it is sheared several times in a single pass. This is how our multi-stage mill for bitumen emulsion reaches a fine, stable emulsion.
What a colloid mill gives you
- Stable emulsions and suspensions, because the particles and droplets are small and uniform.
- A smooth texture and uniform consistency in pastes, sauces and creams.
- A consistent particle size distribution when fine grinding.
- One machine for many products: it handles a wide range of materials, from food pastes to paints and adhesives.
Colloidal mill uses
Colloid mills are used in many industries because they handle a wide range of materials.
- Food and beverage: emulsions, suspensions and pastes such as sauces, dressings, mayonnaise, peanut butter and confectionery, for a smooth texture and uniform consistency.
- Pharmaceuticals: stable suspensions, ointments, creams and gels, with the active ingredient (API) spread uniformly through the product.
- Cosmetics and personal care: emulsions and suspensions for creams, lotions and serums, to reach the viscosity, texture and stability required.
- Chemicals, paints and inks: adhesives, paints, inks and coatings, where the mill disperses pigments, dyes and additives evenly.
- Nutraceuticals: suspensions and emulsions that carry the active ingredients and stay stable.
- Chitin and chitosan extraction: fine grinding of the raw material for a consistent particle size distribution, so more surface is exposed to the extraction chemicals. See our grinders for chitin and chitosan.
- Bitumen emulsion: see below.
We also build complete mayonnaise and peanut butter plants.
Colloid mill for bitumen emulsion
Bitumen emulsion is bitumen broken into fine droplets and suspended in water, with an emulsifier that coats each droplet and keeps it dispersed.
For bitumen emulsion we use a multi-stage mill: several rotor-stator stages shear the emulsion several times in a single pass. It breaks the bitumen into droplets down to 0.5 micron and gives a fine, stable emulsion. See our bitumen emulsion plants and how the bitumen emulsion process works.
Colloid mill vs homogenizer and bead mill
A colloid mill is one of several machines that make products finer and more uniform. We make all four below, and they do different jobs.
| Colloid mill | High shear homogenizer | Bead mill | High-pressure homogenizer | |
|---|---|---|---|---|
| How it works | The product is sheared in the narrow gap between the polished surfaces of a high-speed rotor and a fixed stator | Rotor blades draw product into the work head and force it out through openings in the stator | Grinding beads, driven by an agitator in the grinding chamber, grind the solids | A high-pressure pump homogenizer |
| Fineness | A few micrometres; down to 0.5 µm with our multi-stage mill on bitumen emulsion | Low micron size in a single operation | Up to 1 micron, or 50–500 nm | Nano range |
| Typical products | Emulsions, suspensions and pastes: food, pharma, cosmetics, chemicals, bitumen emulsion | Emulsions, dispersions, powders to dissolve or disperse, particle size reduction | Water- and solvent-based slurries: paints, inks, coatings, food, pharma | Milk products, cell disruption, infusion solutions, microemulsions |
| Our range | This page | High shear homogenizers | Bead mills | High pressure homogenizer |
Which one fits your product:
- Pastes, emulsions and suspensions that must come out fine and uniform: a colloid mill.
- Powders to disperse or dissolve, or continuous inline processing, from 15 to 200,000 L/hr: a high shear homogenizer.
- Solids to grind to the nano range in paints, inks and coatings: a bead mill. Our homogenizers can prepare the premix.
- Nano-range emulsions such as milk products: a high-pressure homogenizer. It works best when fed a uniform, fine premix.
Test your product before you buy
There’s no better way to test a machine than on your own product. Run a trial in our fully equipped laboratory and see exactly what results you get, and how fast. If you need longer, our rental program lets you keep a machine, pre-configured to your requirements, for as long as you need. See trials and rentals.
Frequently asked questions
What is a colloidal mill used for?
To reduce the size of particles or droplets in a liquid so the product is uniform and stable. Typical products are sauces, dressings, mayonnaise and peanut butter; pharmaceutical suspensions, ointments, creams and gels; cosmetic creams and lotions; adhesives, paints, inks and coatings; nutraceutical emulsions; fine grinding in chitin and chitosan extraction; and bitumen emulsion.
What is the working principle of a colloid mill?
A rotor turns at high speed next to a stationary stator, and their polished surfaces are very close together. The product flows through the gap between them, where intense mechanical and hydraulic shear breaks down particles and droplets and spreads them evenly through the liquid. A multi-stage mill repeats this several times in one pass.
Is a colloid mill the same as a homogenizer?
Not quite. Both a colloid mill and a high shear homogenizer use a rotor and a stator. In a colloid mill, the product is sheared in the narrow gap between two polished surfaces. In a high shear homogenizer, the rotor forces the product out through openings in the stator. A high-pressure homogenizer is a different machine again: a pump homogenizer for the nano range.
What particle size can a colloid mill achieve?
Colloid mills bring particles and droplets down to a few micrometres. On bitumen emulsion, our multi-stage mill reaches droplets down to 0.5 micron. For the nano range, a bead mill (50–500 nm) or a high-pressure homogenizer is the right machine.
Should I choose a colloid mill or a bead mill?
Choose a colloid mill for emulsions, suspensions and pastes. Choose a bead mill to grind solids in water- or solvent-based slurries down to the nano range, for example in paints, inks and coatings.
Can a colloid mill be used for bitumen emulsion?
Yes. For bitumen emulsion we use a multi-stage mill: several rotor-stator stages shear the emulsion several times in one pass, giving droplets down to 0.5 micron and a stable emulsion. See our bitumen emulsion plants.
Can I test my product before buying?
Yes. You can run a trial in our laboratory, or rent a machine configured to your requirements. See trials and rentals.
