The complaint arrives by email and it is always the same complaint. The floor looked terrific on the Monday, acceptable on the Friday, and by the middle of the month it looked worse than it did before anyone touched it, and the client would like to know what they paid for.

I have had that email from a design studio in Southwark, from a dental practice in Acton and from a distribution office near Wembley, and on every one of those jobs the encapsulation had been done properly. The method did what the method does. The problem was what it had been asked to do.

What does encapsulation do to soil?

It crystallises it and then hands it to a vacuum cleaner.

An encapsulation product is a polymer with surfactant properties. You spray it into the pile, agitate it in with a cylindrical brush or a counter-rotating machine, and the surfactant does the usual job of loosening soil from the fibre. Then the clever part: as it dries, the polymer sets into brittle crystals that hold that soil in a form which no longer sticks to the yarn. Vacuum afterwards, and vacuum again the next day and the day after, and the crystals and their cargo leave the building in a bag.

Very little water goes down, the floor is walkable in under an hour, and the cost per square metre is a fraction of extraction. For interim maintenance of commercial carpet that gets vacuumed properly every night, it is a good method and I use it constantly.

What the polymer can grab

Loose particulate, bonded particulate, light oily film. Soil, in other words, which is material sitting on and around the fibre. The polymer works by surrounding things that are physically present in the pile. Everything that follows in this piece comes from that one sentence.

Why can encapsulation not move an old set stain?

Because a set stain is a change in the colour of the fibre, and there is nothing physically present for the polymer to surround.

Coffee is the everyday example. Tannins in coffee behave as dye, and on a nylon office carpet they bond to the fibre in the same way the manufacturer’s own dye did. Wine, tea, fruit squash, ink, food colouring and the brown ring left by a plant pot all do versions of the same thing. After a few weeks, helped along by light, heat and foot traffic, that bond is as permanent as the carpet’s original colour. A surfactant cannot lift it because it is not sitting on top of anything.

Removing it means chemistry that acts on colour, which is reduction or oxidation, applied to one spot with dwell time and usually heat, and tested first because it can take the carpet’s dye along with the stain. That is a different visit with different products and a different price, and it happens before or after an encapsulation clean rather than during it.

The thirty-second test on your own floor

Wet a white cloth with warm water, press it hard onto the mark for ten seconds and look at the cloth. Colour transfer means there is still material sitting there and the mark will respond to cleaning. A clean cloth and an unchanged mark means the fibre itself has been coloured, and no amount of encapsulation, and no number of repeat visits, will alter it. Do this before you accept a quote that promises a stain will come out.

Why does the floor look worse in week three?

Three mechanisms, and they arrive on slightly different schedules.

The first is wicking. Old spills in a commercial carpet rarely stop at the pile. Liquid travels down to the backing and dries there, invisible, sometimes for years. Encapsulation puts moisture back into the pile, and as that moisture evaporates upward it carries dissolved residue from the backing with it, depositing it at the tips of the yarn where you can see it. A spill that had faded to a shadow reappears as a defined brown patch, and it does it two or three days after the clean rather than on the day, which is why nobody connects the two events.

The second is soil that was released and never removed. Crystallised soil that stays in the carpet gets walked on, crushed back into the pile and re-bonded. A fortnight on, that floor is carrying its old soil plus a polymer that has been ground into it, and it looks tired.

The third is residue. Over-application, the wrong dilution, or a product chosen for price over quality leaves a film that stays tacky enough to attract soil, and a carpet with sticky residue in it resoils faster than it did before the clean. That is the one that produces the angry email, because the floor does get dirtier more quickly than it used to.

Oily soil deserves a mention of its own. Encapsulation products carry limited solvency, and a traffic lane in a building where people walk in from a car park or a kitchen holds a greasy film that the polymer only partly lifts. Polypropylene makes it worse, because oil has an affinity for the fibre that water-based chemistry struggles against. Those lanes come back darker and faster than the rest of the floor, and a client watching one lane fail while the open plan holds up reasonably concludes the work was rushed, when the truth is that the lane needed a solvent pre-spray and extraction.

Wicking runs on its own timetable

I now warn every commercial client about the three-day window before I start, particularly in tea points and under desks where drinks have been going over for a decade. It costs me nothing to say it and it saves an argument. On the dental practice job in Acton, four old spill marks came back in the waiting room by the Thursday, and because the practice manager had been told on the Monday, the conversation was about extraction rather than about a refund.

What is the most common way encapsulation gets done badly?

The vacuuming, and it is not close.

The entire method depends on a machine coming along afterwards with enough airflow and enough brush agitation to lift dried crystals out of the pile. What most buildings have is a cleaning operative with a lightweight backpack vacuum and a plain suction floor tool, no brush bar, moving at walking pace because there are four floors to do before six in the morning. Crystals stay where they are. The soil the encapsulation released stays in the building, and by week three it is back in the fibre.

If a contract does not specify the vacuum, the contract has not specified the clean. I would rather a client spend money on upright vacuums with working brush bars and a realistic nightly time allocation than on more frequent encapsulation visits from me, and I say that in writing when I quote.

Dilution is the quiet second offender. Encapsulation products are mixed by ratio and most operatives mix by eye, and a product at double strength does not clean twice as well, it leaves twice as much polymer in the pile. I have taken over contracts where the previous firm’s tub was lasting half as long as it should have, which told me everything about why the floors were resoiling in a month.

The other failure is scope

Encapsulation on a floor that has never had a restorative clean is a cosmetic gesture. In an office in Ilford I encapsulated a floor where the carpet had been down for eleven years and had never been extracted once, and the improvement lasted about a fortnight, because everything below the top third of the pile was untouched and steadily migrated upward. That job should have been priced as an extraction with encapsulation afterwards as maintenance, and I took the easier booking, and the client was right to be unimpressed.

Where should encapsulation sit in a maintenance plan?

Underneath extraction, not instead of it.

The shape that works in most London commercial buildings is a restorative hot water extraction every twelve to eighteen months depending on footfall, encapsulation of traffic lanes and hot spots between those, spot treatment of individual stains as they happen and within days rather than months, and nightly vacuuming that is specified, timed and checked. Entrance matting long enough that people take three steps on it does more than any of the above and costs less than one visit. Most buildings run two metres where they need six, and the difference lands in the first ten metres of every corridor.

Frequency without restoration is the trap. A building on monthly encapsulation and no extraction is on a schedule that generates steady revenue for a contractor and a floor that declines anyway, and by week three of each cycle it looks the way it looked before the previous visit.

Season matters too, more than most facilities teams expect. A London office takes in grit and wet through the winter and holds it in the lanes, so the sensible point for the restorative clean is late spring, with encapsulation carrying the floor through to Christmas. Booking the big clean in October, which is what most buildings do because budgets run out in March, means paying for a deep clean immediately before the four months that undo it.

What I would rather sell you

Fewer visits and better ones. Three encapsulation visits a year and a proper extraction, rather than nine encapsulation visits and none. It is a smaller invoice, and the carpet lasts longer, and the second of those is the thing that shows up in a dilapidations schedule at the end of a lease.

The Southwark studio took that version. Their tea point still has two brown rings in front of the fridge, which arrived long before I did, and which I have told them twice will need a reducing agent and a test patch rather than another clean.