Centrifuges Explained: How They Work & How to Choose

A centrifuge separates materials by spinning them. At speed, the force pushing outwards is many times stronger than gravity, so a job that would take hours of draining or settling is done in minutes. In botanical processing that usually means one thing: getting liquid out of plant material quickly and completely.

This guide covers how centrifuges work, the two main types you will come across, and what to check before you buy one.

What a centrifuge does

Left to stand, a mixture of solids and liquid separates slowly under gravity. A centrifuge speeds this up enormously by spinning the mixture so the force acting on it is hundreds or thousands of times greater than gravity. Denser material is pushed outwards, and lighter material is left behind.

In practice this lets you:

Separate solids from liquids: recover liquid from wet plant material far more completely than draining or squeezing.
Reduce moisture: spin washed material close to dry before it goes into a freeze dryer or drying rack.
Clarify a liquid: pull fine suspended particles out before filtration.

Tube centrifuges and basket centrifuges

Type	How it works	Typical capacity	Used for
Tube (lab) centrifuge	Sealed tubes spin in a rotor; solids form a pellet at the bottom of each tube	Millilitres per tube	Sample preparation and testing
Basket centrifuge	Material sits in a perforated basket lined with a filter bag; liquid is flung through the mesh into the outer bowl and drains away	Kilograms per cycle	Solid-liquid separation in botanical processing

For working with plant material at any volume, a basket centrifuge is the tool. The rest of this guide focuses on those.

How a basket centrifuge works

Load: wet material goes into a filter bag that lines the perforated basket.
Spin: the basket accelerates and the liquid is forced outwards through the bag and basket wall.
Collect: the liquid hits the outer bowl and runs out of a drain port into a collection vessel.
Unload: the plant material stays in the bag, spun close to dry, ready to lift out.

The filter bag decides how clean the liquid is. A finer micron rating holds back more fine particles. A coarser one drains faster.

RPM and g-force are not the same thing

Spec sheets usually quote speed in RPM, but what separates material is the force, known as relative centrifugal force (RCF) or g-force. It depends on both the speed and the radius of the basket:

RCF = 1.118 × 10⁻⁵ × radius (cm) × RPM²

For example, a basket with a 15 cm radius spinning at 3,000 RPM produces about 1,500 × g. Because force rises with the square of the speed, doubling the RPM gives four times the force. When you compare two centrifuges, compare g-force at the basket wall, not RPM alone.

Where a centrifuge fits in a botanical workflow

After a wash or soak: separate the liquid from the plant material quickly, so contact time stays short and controlled.
Before filtration: removing most solids first means your filters clog less and run faster.
Before drying: spinning washed material close to dry shortens drying time in a freeze dryer.
Before evaporation: a cleaner liquid going into a rotary evaporator means less residue to deal with later.

How to choose a centrifuge

1. Capacity per cycle. Work out how much material you handle in a typical batch. Capacity is quoted as kilograms of material per cycle, and running several short cycles is normal. Sizing for your usual batch rather than your largest keeps the machine balanced and efficient.

2. Speed and control. Adjustable speed lets you match the force to the material. Gentle settings suit delicate material; higher settings recover more liquid. Programmable cycle times make results repeatable.

3. Temperature control. A jacketed centrifuge has a hollow wall that chilled fluid circulates through, holding the bowl at a set temperature during the spin. If temperature affects what ends up in your liquid, a jacket keeps conditions consistent from the first cycle to the last.

4. Materials and build. Look for stainless steel contact parts and seals that are compatible with any liquids you use. A solid, well-balanced basket matters more than headline speed.

5. Safety features. A lid interlock, imbalance detection and controlled braking are essential on any machine that spins kilograms of wet material. If you work with flammable liquids, use the centrifuge only in a properly ventilated area that is suitable for them, and follow the manufacturer's instructions.

Getting the best from a centrifuge

Balance the load. Spread material evenly around the basket. An uneven load causes vibration and wears the bearings.
Don't overfill. Leave room for the bag to sit flat against the basket wall.
Pick the right bag. Choose a micron rating that suits the liquid you want to collect. See our filtration guide for help.
Clean between runs. Rinse the basket, bowl and drain while residue is still soft.

Centrifuge FAQs

What's the difference between RPM and g-force? RPM is how fast the basket turns. G-force is how hard the material is pushed outwards, and it depends on both speed and basket size. G-force is the number that matters for separation.

Do I need a jacketed centrifuge? Only if you need to hold the bowl at a set temperature during the spin. For general solid-liquid separation, a standard centrifuge does the job.

Centrifuge or filter? Both. A centrifuge removes the bulk of the solids quickly, and a filter does the fine clean-up afterwards.

How much can I process per run? It depends on the machine. Our Helios centrifuges take up to 3 kg of material per cycle.

Shop centrifuges

We stock the Helios V-3000 Centrifuge and the temperature-controlled Helios Jacketed Centrifuge, both with a 3 kg capacity. Browse the full centrifuge range, or call the Barnsley showroom on 0114 229 1807 for help choosing.