Carpet Cleaning FAQ

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Carpet Cleaning FAQ

Carpet Manufacture

Knowing a little about carpet construction helps an awful lot when it comes to understanding how to clean them.

Carpets broadly comprise two parts, the pile yarn (the top bit that you can see) and the backing yarn (the underneath bit that you don't see).

The backing yarn holds everything together and forms the matrix that holds the pile yarn.

There are three ways in which carpets are made:


Account for about 20% of the market. Expensive but long lasting and high quality. Commonly known as Axminster or Wilton. Note that Axminster and Wilton are 'manufacturing methods' that originated in those places, not brand names. Perfectly genuine Axminster carpets may be made in Belgium.

With both methods the pile and backing yarns are woven together at the same time. It's a slow process, which accounts for their high cost.

Woven carpets usually have very dense pile.

How can you tell? Look at the backing - you will see the coloured pile yarn woven through the backing.


The vast majority of carpet is tufted, around 75% of the UK market.

Tufted carpet is made by using a pre-woven backing cloth, into which the pile fabric is tufted or punched. The carpet is usually 'secondary backed' with a rubber, polyurethane or foam backing.

This is done on huge tufting machines at very high speed, giving a very economic manufacturing cost.

Tufted carpet is also called twist pile, cut pile, loop pile, cut and loop pile, Saxony or sculptured pile. The manufacturing method is broadly the same.

The quality depends on many factors, but an important one is the pile density - measured in threads per square inch. The denser the pile the better. Look at a cheap tufted carpet and you can see the backing through the pile.


Several methods are used to bond either individual yarns or a web of fibres onto a pre-woven backing. Best-known trade name is Flotex. Found in domestic kitchens and commercial premises.

Flotex is completely waterproof, highly stain-resistant, incredibly durable and easy to clean. Carpet tiles are made by a similar process and for our purposes can be treated in the same way.

An excellent guide can be found at here

Pile and Backing Materials

Pile and backing yarns fall into two categories; natural or synthetic.

Natural yarns are hessian or jute for backing yarn, and wool for the pile yarn (or more often wool/nylon).

Synthetic yarns include nylon, polypropylene, and polyester for the pile yarn. Backing is almost always a cheaper synthetic.

So four possible combinations are possible:

Pile Backing

  1. Natural Natural
  2. Natural Synthetic
  3. Synthetic Natural
  4. Synthetic Synthetic

How can you tell which is which? Simple, you need a small pair of scissors, some tweezers and a lighter. Snip off a sample piece of yarn from either the pile or backing - use a spare piece of carpet or find a little used corner.

Hold the sample in the tweezers and move the flame towards it slowly.

Wool or 80/20 wool/nylon will glow and eventually ignite with a smell like burning hair. All synthetics will tend to shrink away from the flame, 'bead' over and smell like burning plastic - an acrid chemical smell.

In practice the choice of fibre depends on the application, the site, the traffic, and the cosmetic appeal. However, it's useful to know that natural fibres (wool) don't attract soiling (dirt) whereas synthetics do. On the other hand wool can be stained badly, but most synthetics can't.

Now you know the basics, we can address the most common concerns about DIY carpet cleaning.

Carpet Cleaning Concerns

Two common concerns are 'will the carpet shrink' and 'will the colours run'. There are only three causes of these two problems. And the likelihood of them happening depends on the construction of the carpet.

Let's examine the problems:

Will the carpet shrink?

It's a common fallacy that wool carpets are prone to shrinking. Rare in practice - have you ever seen a sheep shrink in the rain?

Only shrinkage of the backing of a carpet can cause a problem. If the pile were to shrink, you would never know.

If the carpet has a synthetic backing, it can't shrink because it is impervious to water. A natural fibre backing can, and will, shrink if water gets to it.

If the carpet is of woven wool or wool/nylon construction, the pile is so dense and so absorbent (wool can absorb 40% of its own weight in water) that it's almost impossible to get water to reach the backing when cleaning. Only a flood is likely to cause shrinkage.

With a cheap synthetic pile natural backed carpet, the risk of shrinkage is high. The water will run off the synthetic pile straight onto the natural backing. Nylon, for example, can only absorb about 1% of its weight in water.

If a carpet does shrink, a competent carpet fitter can usually stretch it back to its former state.

Will the colours run?

This irreversible problem can only happen to natural pile carpets. Wool starts life as off white and is piece dyed to make various colours.

Modern dyes are so good, however, that correct cleaning is unlikely to affect them.

Synthetic pile yarns are manufactured to be the colour they are. If it's blue, it was made blue, not dyed blue. It would be difficult to remove the colour if you wanted to. Only bleach would affect the colour.

One odd problem is that called 'browning'. When a carpet dries out brown patches appear on the surface. This is caused by water reaching the backing of the carpet. If the backing is a natural fibre, the vegetable dye used to colour it can be affected. This will then 'wick' up the pile and appear on the surface of the carpet.

Browning looks terrible but is actually easy to fix. The carpet is simply sprayed with a specialist chemical and the browning usually disappears.

Problems and their Causes


Excessive water use can cause two problems when cleaning carpets.

If you excessively wet a carpet when cleaning it and the water reaches the backing material, it could cause or exacerbate shrinkage.

This will only happen if the backing is a natural fibre. Synthetic backings can't shrink.

Excessive water can also cause dye bleed, or colour run, although this is rare with modern dyes. Excessive water can also cause the 'browning' phenomenon.

Excess heat

The use of very hot water can cause or exacerbate shrinkage and dye bleed. As a rule of thumb, if you can't put your hand in the water it's too hot for cleaning your carpet.

Incorrect chemical use

Carpet cleaning chemicals are highly specialised. Use only those specially made for carpet cleaning. Do not ever be tempted to use household washing powder/liquid or any other chemicals for cleaning carpets. It will result in a sticky mess that will attract soiling.

Make sure you follow the dilution rates quoted on the container. More is not better. Use a measuring jug and get it exactly right. "About two glugs" isn't acceptable!

Carpet cleaning methods

The most common carpet cleaning methods available to the DIY cleaner are:

Spray Extraction Cleaning

Sometimes called hot water extraction or steam cleaning, this is probably the most popular method of carpet cleaning. It offers the deepest cleaning and flushes out more dirt than other methods.

In addition, spray extraction machines are able to clean stairs and upholstery.

A carpet spray extraction machine will have two tanks. One is filled with a water and detergent solution, which is sprayed into the carpet pile under pressure, shifting the dirt.

The liquid and dirt is then removed by a vacuum and returned to the other, the recovery tank.

Two basic types of spray extraction cleaner are available, the standard type has a solution hoes & a vacuum hose connecting the machine to a floor wand or upholstery/stair tool. These machines work well in confined areas and are versatile enough to clean car seats, caravan interiors etc.

Self contained extraction machines do not have the hoses - the spray nozzle(s) and vacuum recovery head are built into the body of the machine, often with a powered brush in between. The entire machine is moved over the carpet making them much faster in use on large areas. Many self contained extractors have the option of using hoses & wands to make them more flexible.

Spray Extraction Machines

Extraction cleaners can be purchased or hired. Affordable machines for purchase include the Numatic 'George' or the Vax 6155. Self contained extractors are usually beyond the budget of DIY users, but can be hired from DIY stores & hire shops.

Hire can often be a better choice. Machines like the Rug Doctor are similar to those used by professional cleaners. The Rug Doctor is a self contained extractor and has a powered brush, so the process is 'spray/scrub/vacuum' which gives faster cleaning and better results.

Several factors are crucial for good results:

Solution pump pressure makes a big difference. A machine giving 1 bar pressure won't clean as well as one giving 3 bar. Some domestic machines don't actually have a pump at all! - They are a waste of time in my experience.

The vacuum doesn't just remove surplus water; it is a vital component of the cleaning process. The more vacuum power the better. The purpose of the vacuum is to pull the water through the carpet pile, which of course removes the dirt.

Spray Extraction is an integral process. If you were to spray first then vacuum afterwards the results would be very poor.

A more powerful vacuum, whilst it will give better cleaning results, won't necessarily remove more water from a carpet or leave it any dryer. Drying times depend on the carpet fibre.

Wool or wool mix carpet pile absorbs water and the vacuum cannot remove that. Synthetic fibres hold very little water, so recovery is higher.

You can tell what the carpet pile is made from the result of spray extraction cleaning. Solution and recovery tanks are usually of similar size. On a synthetic pile carpet you will recover up to 90% of the water, but with wool it's only about 50%.

Many domestic machines have very small tank capacities, some as low as 5 litres. They still work, but you have to frequently stop to empty and refill the tanks.

Spray Extraction Technique

Clear the room of smaller items - large items like the sofa can simply be moved around the room. Vacuum the carpet thoroughly.

For very dirty carpets a pre-spray, usually called Traffic Lane Cleaner can be applied. Set up the machines as instructed.

Start in one corner and make a pass with the wand up to and parallel with the skirting board. Don't over reach - two or three foot at a time is fine.

The second pass should overlap the first by 50%. The third pass should overlap the second again by 50% and so on. This way you will get even cleaning and maximum soil removal.

Work your way across the room, and then start a new series of passes.

If the carpet is extremely dirty, make a series of passes at right angles to the first, but don't overlap them.

In the unlikely event that this doesn't remove the dirt - STOP. Wait for the carpet to dry completely before trying again.

Once you have covered the entire area, return to your starting point and go over the carpet again with only the vacuum switched on (in other words, don't spray). This will remove surplus moisture that has 'wicked' up the pile.

Ventilation is the key to drying carpets - open the windows and get a through draft.

Stay off the carpet until dry - if you have to walk on it, wear clean house slippers or go barefoot. Take care - wet carpets are slippery.

Dry Foam Cleaning

Whilst various machines and techniques are used for dry foam cleaning, they all rely on the use of a special shampoo.

The principle is that water and detergent are applied as foam, so less moisture is present. The shampoo crystallises as it dries, trapping the dirt, which is vacuumed away when the carpet is dry.

Advantages are fast drying times and no risk of over wetting. Disadvantage is that, in my opinion, it is only a surface clean.

Dry Powder Cleaning

With this system, absorbent granules (impregnated with detergent) are brushed into the carpet pile, left for a short time, the vacuumed away.

Advantages are that no water is used and the room isn't out of use for much time.

Again, in my opinion only a surface clean.

Carbonated Water Cleaning

Operated mainly as a franchise, the cleaning method is apparently to inject fizzy water into the carpet and agitate with an absorbent cotton pad, fitted to a floor-scrubbing machine. With 30 years in the trade, I just can't see how this is supposed to work.

Spot and Stain Treatment

The pile fibre of a carpet has a big influence on how easily stains can be removed. Synthetic fibres don't really stain much, whereas wool can stain badly due to absorption.

The most important thing is to correctly identify the stain. If you were present when the stain occurred it's easy, but if not, a little detective work is called for.

Stains near occasional tables are often beverages; stains near a dressing table are usually make-up. I'm sure you get the idea. Smell can also give you some clues!

The second most important thing is to react quickly! The longer a stain is allowed to remain, the harder it will be to remove it.

Spot and Stain Technique

Step 1. Remove any solids with a spoon, working from the outside of the stain in.

Step 2. Blot the stain with an absorbent material. I find paper kitchen roll to be best. It's very important to blot the stain, not rub it. You want to absorb as much as possible.

Step 3. Treat with a stain remover.

Stain Remover Products

If you don't have a specialised carpet stain remover, you can often use household chemicals. An excellent resource is on the Fabric Link site

I'd recommend three companies for carpet stain removal products, /specifics.htm Stain Devils - available in many supermarkets or within 24 hours by post, Rug Doctor, mainly found in DIY sheds and Prochem, mainly trade and available at most janitorial suppliers (see your local Yellow Pages).

These websites all have excellent advice on stain removal.

To give an idea of the products available, Stain Devils offerings include:

SD No. 1 removes stains such as ballpoint pen, beer/larger, crayon, ink roller ball, ink stamp pad, liqueurs, pencil, spirits and typewriter ribbon.

SD No. 2 removes stains such as blood, cream, cream cheese, egg, egg white, ice cream, milk, sperm, starch and yoghurt.

SD No. 3 removes stains such as adhesives, chewing gum, correction fluid, glue, nail varnish, and rubber cement.

SD No. 4 removes stains such as caramel, cocoa, coffee, cola, deodorant, ink fountain pen, iodine, nicotine, tea, tobacco, urine and yellowing.

SD No. 5 removes stains such as body lotion, butter, carbon, clay, cod liver oil, cooking oils, curry, dirt, earth, engine oil, eye shadow, fat, food colouring, foundation cream, grass, grease, hand cream, lipstick, make-up, margarine, mayonnaise, motor oil, mud, pollen, poster paint, rouge, salad dressing, salad oil, sauces, shoe polish, suntan cream, vegetable oil and watercolour paints.

SD No. 6 removes stains such as baby food, beetroot, bird droppings, fizzy drinks, fruit, fruit juice, jam, jellies, marmalade, mildew, mould, perfume, red wine, sorbets, soy sauce, vegetable stains.

SD No. 7 removes such stains as ironmould and rust from fabrics, baths and tiles.

SD No. 8 removes stains such as candle-wax, paint, resin, tar and wax polish.

SD No. 9 removes stains such as felt tip pen and highlighter pen.

SD No. 10 removes stains such as BBQ sauce, chocolate, gravy, ketchup, mustard and spices.

See Also