A polymer in the solution dries into a brittle crystal around each soil particle, breaking its bond with the fibre so it can be vacuumed out.

The solution is applied and agitated so it reaches the soil in the pile. Surfactants release the soil from the fibre in the usual way.

As the carpet dries, the polymer changes state. Instead of leaving a soft tacky film like a traditional shampoo, it crystallises hard and brittle, encasing the suspended soil.

The encapsulated particles no longer adhere to the fibre, so ordinary vacuuming lifts them out. Traffic also breaks the crystals free, which is why encapsulated carpet often continues to improve over the following days.

Because there is no tacky residue, the method does not cause the accelerated re-soiling that gave older low-moisture methods a poor name - provided the polymer is not over-applied.

A sprayer for application and an agitation machine - typically a counter-rotating brush or oscillating pad machine - plus a good vacuum for the follow-up.

Application can be by pump sprayer, electric sprayer or through the machine's own tank. The requirement is even coverage without over-wetting.

Agitation is what gets the chemistry to the soil. Counter-rotating brush machines are the usual choice because they work the solution into the pile without the distortion risk of a single-disc rotary.

Bonnet pads on a rotary can be used, though that becomes closer to bonnet cleaning and reaches less of the pile.

The vacuum is the piece most often under-specified. A weak or clogged vacuum will not lift encapsulated soil, and the whole method depends on that step.

No extraction machine, hoses or water supply is needed, which is why the method suits upper floors and buildings with difficult access.

Encapsulation cleans the pile and leaves soil to be vacuumed out; bonnet cleaning transfers soil onto an absorbent pad and only reaches the pile tips.

In bonnet cleaning the pad does the removal, and it loads quickly - a soiled pad redeposits soil, so pads must be changed frequently.

Encapsulation does not rely on the pad to carry soil away. The polymer handles removal at the vacuuming stage, so agitation can be brushes rather than absorbent pads.

Depth of clean differs. Brush agitation reaches further into the pile than a bonnet, which sits on top.

Both are interim methods with short drying times, and both suit occupied buildings.

Where bonnet cleaning has been used with traditional chemistry, encapsulation products are often specified afterwards because they help lift accumulated residue rather than adding to it.

Yes - until the encapsulated soil is vacuumed out it is still in the carpet, and this is the most commonly skipped step in the method.

The chemistry breaks the soil's bond with the fibre; it does not remove the soil. Removal is mechanical and happens at the vacuum.

The carpet often looks clean immediately, because encapsulated soil is less visible. That appearance is what leads people to conclude vacuuming is optional.

Best practice is a thorough vacuum once fully dry, ideally with a machine that agitates the pile, and again during the following routine cycles.

Where a building's daily vacuuming is thorough, some of this happens automatically. Where it is not, the encapsulated soil accumulates and the method appears not to work.

Contract specifications should state the follow-up vacuum explicitly, because it is usually performed by a different team from the one that cleaned.

Commercial synthetic carpet - cut pile, loop and carpet tiles - in occupied buildings. It is less suited to heavy grease, deep soil and delicate natural fibre.

Nylon and polypropylene commercial carpet responds well and is where the method is used most.

Carpet tiles are a particularly good fit, since low moisture avoids the edge curl and adhesive problems that over-wetting causes.

Heavily soiled carpet, food service areas and anywhere with significant grease need extraction. Encapsulation cannot flush what it cannot reach.

Wool can be cleaned with wool-safe encapsulation products at appropriate pH, with gentle agitation - check the product and the carpet manufacturer's guidance.

Long pile and shag do not suit brush agitation.

For restorative cleaning of any carpet, extraction remains the method; encapsulation is chosen for what it does between those cleans.

Usually within an hour or two, which is the practical reason the method is chosen.

Very little moisture is introduced, so drying is fast. In a normally ventilated building an area cleaned in the evening is ready before the next working day, and often much sooner.

Air movers shorten it further where the schedule is tight.

Carpet should be dry before traffic returns. Walking on damp encapsulation chemistry picks it up on shoes and transfers it to hard floors.

This short cycle is what allows cleaning to be scheduled around occupancy rather than requiring a shutdown, and it is why the method dominates interim maintenance in offices, retail and hospitality.

The trade-off remains that it is interim: quick and frequent, rather than deep and occasional.

It can if the product is over-applied or vacuuming is inadequate, and the answer is a periodic extraction clean.

Each application leaves polymer that should be vacuumed out with the soil. Where vacuuming is insufficient, polymer accumulates in the pile over repeated cleans.

The symptom is carpet that feels slightly stiff or crunchy, or that stops responding to encapsulation as it used to.

Over-application accelerates it. Following the dilution and coverage rates rather than applying generously is the main control.

A restorative hot water extraction removes accumulated polymer and deep soil together, which is another reason the two methods belong in the same programme.

Set the extraction interval by traffic and soil rather than by calendar alone - an entrance area needs it far sooner than a private office.