The rug goes off dirty and comes back looking better than it has in years. Two days later, once it’s been walked on and warmed by a radiator, the room smells like a cellar. The owner rings the cleaner, the cleaner suggests airing it, and everybody spends a fortnight being polite while the smell settles in.
This happens more than the trade admits, and in the large majority of cases it has one cause. The rug was not dried properly. Everything else – the urine argument, the “it must have been there before” argument, the latex argument – is either a second-order effect or a defence.
What is the musty smell telling you?
Micro-organisms need moisture, warmth and something organic to eat. A rug’s foundation is cotton, wool or jute, its pile is wool or viscose, and a warm London flat supplies the rest. Leave any of that damp for long enough and bacteria and fungi go to work, producing the volatile compounds our noses read as musty, earthy, or old-book.
The threshold is time. Below about twelve hours you’ll get away with it. Past twenty-four you’re in trouble, and past forty-eight the smell is a certainty in a jute-wefted rug. That’s a drying failure, and it belongs to whoever had custody of the rug.
Jute is the worst material for it. Jute wefts run through most Persian and Indian rugs made for export and through nearly every tufted rug, and jute wet for two days smells like wet cardboard for years afterwards. Cotton is more forgiving, wool more forgiving still.
Why wool smells like a wet dog for a day
Set aside one thing that isn’t a fault. Wool damp has an odour of its own – lanolin, protein and the natural scent of the fibre – and a freshly washed wool rug will smell distinctly sheepy for the first day or two. It fades. It’s stronger on hand-knotted rugs with high lanolin content and on anything that’s had a proper immersion wash.
The distinction is direction. A wool smell diminishes daily. A microbial smell gets stronger, and strengthens further whenever the rug is warmed or walked on, because heat and pressure push more of it into the air.
How long should a rug take to dry?
A properly equipped plant should have a wool rug dry within four to eight hours of coming out of the wash. That means centrifuged or wrung to remove the bulk of the water, then hung or laid flat in a heated room with air movement across both faces and dehumidification pulling moisture out of the space.
Air drying in a garage in December takes three days and gives you exactly the result described at the top of this page.
That’s why in-home rug cleaning worries me. A rug cleaned on your living room floor with a hot water extraction machine takes on a great deal of water, sits on top of an impermeable underlay or a solid floor, and dries from one face only. The bottom stays wet for a day and a half in a flat off Northcote Road with the windows shut and the heating on a timer. That’s a drying failure too, and the equipment used doesn’t change it.
What a proper drying room does
Warm air holds moisture; moving air carries it away from the surface; a dehumidifier takes it out of the room so the air can keep working. All three have to run together. A hot room with still air just makes a humid room, which is how rugs come back smelling of the place they were dried.
Ask any cleaner what their drying room runs at and how long a 2m x 3m wool rug stays in it. A firm that washes rugs properly will answer in about four seconds. A firm that doesn’t will talk about their machine.
Could the smell have been in the rug before it left?
Sometimes, and this is where the argument gets honest on both sides.
Dried urine is close to odourless. The salts sit in the foundation, dormant, until moisture arrives – then they rehydrate, the bacteria wake up, and the ammonia and sulphur compounds come off it hard. A rug that smelled of nothing on Tuesday can smell like a cat sanctuary on Thursday, and the moisture that triggered it came from the clean.
That doesn’t make it the client’s fault, and it doesn’t make it the cleaner’s fault either. What makes it somebody’s fault is failing to check first. A urine lamp takes ninety seconds and a moisture-and-salts check on the reverse takes about the same. Any rug coming in for wash should be inspected for contamination before it goes near water, and any found should change the process from a wash to a decontamination.
Why a light clean makes old urine worse
Surface cleaning puts in enough moisture to reactivate the deposits and nowhere near enough flushing to remove them. You get all the smell and none of the removal. A tufted rug from a flat on Royal Hill came to me after a “refresh” by another firm – one dog, three years, four spots – and the smell after their visit was worse than anything the owner had lived with before.
Urine in a rug needs volume. Full immersion, repeated flushing, chemistry to break down the salts and the bacterial residue, and then the same controlled drying as anything else. There is no light version of that job.
Whose fault is it?
The cleaner’s, in the great majority of cases, and I’d say that in front of anyone in this trade. The rug was under-dried, or it was rolled while damp, or it was wrapped in polythene for delivery before it had finished, which seals the moisture in against the pile and is the single most avoidable mistake anybody makes.
A share of the blame belongs elsewhere. Rugs put straight back down on a cold solid floor in an unheated room will pick up moisture from underneath – a stone floor in a converted place near Chatsworth Road did exactly that to a perfectly dry rug in November. Rugs stored rolled in a loft after cleaning. Underfloor heating switched off for the summer with a rug sitting on tile.
And a share belongs to the rug. Tufted rugs with a latex adhesive layer between the pile and the scrim develop a distinctive smell as the latex ages and oxidises, and washing accelerates it. That smell reads as rubbery and sour rather than earthy, it can’t be removed, and no cleaner should promise otherwise.
The questions to ask before you hand a rug over
Where does the cleaning happen. What does drying involve and how long does it take. Do you check for urine before washing, and what changes if you find it. Is the rug wrapped for return, and is it wrapped after it’s fully dry.
Four questions. The answers sort the trade out quickly.
One more if the rug matters to you: ask whether they wash by hand or run everything through a machine on the same programme. Fringes, dye-sensitive reds, silk highlights and old cotton foundations all want different handling, and a firm with one process for every rug will give you one result for every rug.
Can the smell be got out once it’s there?
Usually, if it’s caught early and if the cause was drying rather than contamination. Rewash, decontaminate the foundation, dry it properly this time, and most rugs come back clean-smelling. The cost falls on whoever caused it, and a reputable firm will do it without an invoice and without an argument. If a cleaner tells you to air it in the garden and ring back in a month, they’re waiting for you to give up.
Deep-set microbial growth is different. Once fungal growth has established in a cotton foundation you can have staining from the reverse, weakened warps, and an odour that returns every humid week in July. Chlorine dioxide treatment and ozone chambers get used at this stage. Both have their place and both are oversold. Ozone in particular gets sold as a miracle and will oxidise wool dyes and weaken fibre if somebody leaves a rug in the chamber too long, which happens. It treats odour in the air and on surfaces; it does very little inside a dense foundation, which is where the problem lives.
When I tell people to write the rug off
A machine-made tufted rug of no particular value with an established musty smell in the latex and the scrim is not worth decontaminating. The treatment costs more than the rug, the outcome is uncertain, and you’ll be listening for the smell every warm evening for the next five years.
Same answer for heavy long-term urine contamination in a rug with a jute foundation. I’ve had two good outcomes and a lot of expensive disappointments, and I now quote those jobs with an honest warning that I’d rather they spent the money elsewhere.
The exception is anything hand-knotted with age or provenance. Those are worth fighting for, and the foundation is usually cotton or wool rather than jute, which improves the odds considerably.
A rug came back to a client in Greenford last year smelling of cellar after a wash by a general carpet firm. It had been rolled in plastic in a van overnight in October and delivered the next morning still cold in the middle. That’s a drying failure, plain and simple, and the firm that did it offered her a discount on her next clean.