What's the best way to clean a car? (You need two buckets)

Times

15-07-2025

Q. Is there such a thing as the perfect way to clean a car and how do I do so without leaving smears or scratches? Also, is paying for hand wash better than going to an automated car wash? TR, Richmond upon Thames
To minimise the risk of scratched paintwork you should adopt the 'two bucket' method: one bucket for diluted shampoo and a second full of clean water, along with a microfibre mitten or cloth, as opposed to a cheap cellulose sponge. After rinsing the car with a hose to soften the dirt and get rid of mud, clean one section of paintwork, then rinse the mitten in the clean-water bucket to avoid putting dirt from the car into the shampoo bucket. Then back it goes into the shampoo to clean the next section of bodywork.
Use a car shampoo, not washing-up liquid or household detergent. There are a couple of reasons. First, washing-up liquid is a strong detergent, designed to get rid of grease and fat. It will do a good job of cleaning off the dirt but it will also clear away any trace of polish, so unless you polish or wax the car after each wash, the paint surface will not be protected and eventually go rather dull. Second, car shampoo normally contains a lubricant to enable the washcloth to slide over the paintwork with much less risk of tiny scratches from the dirt you are washing off.
Avoid washing the car in sunshine or the water will dry quickly, leaving spots and smears. Choose a cloudy day or shaded area and dry the car with a chamois leather or microfibre towel.
Modern water-based paints used by car manufacturers are also more susceptible to corrosive damage from bird droppings, especially if they are left in place for a long time, so try to clean them off the same day, even if you don't wash the whole car. A hose is ideal, or a watering can and soft cloth, but clean gently; overenthusiastic scrubbing can inflict damage to the paint underneath. Tree sap can be a nuisance as well but a decent shampoo will get rid of it after two or three wipes. Again, be gentle.
Products containing shampoo and wax — 'wash/wax shampoo' — leave a trace of wax on the car after rinsing, but the best protection from dirt, sap and bird droppings is washing followed by a polish and wax every so often.
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Car detailing or valeting aficionados will, quite correctly, tell you that polish and wax are two different things. Polish is a mild abrasive designed to remove or minimise swirls and slight imperfections, whereas wax leaves a smooth glossy layer to enhance the shine and give added protection. The best natural wax is carnauba, obtained from South American carnauba trees but there are many resin products which do a similar job. All leave a protective layer over the paint to protect it from sunlight, droppings and road dirt.
Car detailing enthusiasts swear by washing the car, drying it, applying polish, buffing the polish off, then waxing the car and buffing it to a better-than-showroom finish. If, on the other hand, you feel you have better things to do than spend the entire weekend cleaning the car, you can achieve an impressive finish with less effort by using products that are both polish and wax or resin. They contain a very fine abrasive to smooth the surface and fill scratches, and a wax to leave a good shine.
Typical products are Autoglym Super Resin Polish, Turtle Wax Carnauba or Simoniz Liquid Diamond. All of these will remove or reduce slight swirling and leave a wax or resin coating. The coating will be quite thin and won't last as long as a thorough carnauba wax, but the finish is easily good enough to please most car owners. It will last a reasonable time. Treating the car three or four times a year is usually sufficient, and you can tell when the next polish is due because rainwater will not 'bead' on the paint surface.
For some of us, cleaning the car thoroughly is a therapeutic activity; it's not mentally demanding and the results are instant and very visible. Of course, not everyone feels that way and many will simply want someone else to do what they regard as a chore. And why not? For the price of a couple of coffees (or one very posh coffee) you can get a perfectly acceptable job done. But, do you use the automatic machine or go to the disused garage forecourt where a small army of cleaners will descend on your car with sprays, buckets and cloths?
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I've been to lots of hand carwashes and I've never seen any of them adhere to the two-bucket method, but then I pay only about £7 to £10 for a wash and dry. A typical handwash service may foam the car then jetwash it, and then use a cloth from a big shampoo bucket to clean the dirt off. This does risk rubbing the grit and dust from your car, and possibly previous cars, over the rest of the paintwork, causing those swirly scratches.
The jet washers they use to soak and rinse the car shouldn't be a problem provided the doors, bonnet and boot are closed properly, although they have been known to dislodge balance weights from alloy wheels. If the car suddenly starts to vibrate at speed after a carwash, that's probably why. You'll almost certainly get a better result from a specialist valeting service, but you'll pay much more for the extra time it takes.
An automatic car wash is certainly quick and easy; just drive in, let the brushes and driers do their work then drive out. However, an automatic car wash will not clean hard-to-access areas or wheels as well as a hand wash. If the car wash is well maintained, the brushes should thoroughly rinse themselves after each car, but not all are cared for so well.
If the paint does become dull after a few years you can restore the showroom, swirl-free finish by having the paintwork machine-polished by a good car valeting service. The swirls are typically about 1.5 to 2 microns deep and a machine polish will remove the top 2 to 3 microns, but obviously you can do this only a limited number of times before the clear coat — a clear, glossy top coat applied on top of the coloured base layer — gets too thin to give proper protection.
Alternatively, you could get the car treated with a ceramic coating. A ceramic coat is tougher than the clear coat or wax but the car will need a bit of preparation and the overall cost will be about £350 to £500. Afterwards it should be showroom-shiny, much more resistant to swirl marks and the coating should last a few years. DIY ceramic coatings are cheaper, typically £70 to £100 for a kit, but they are thinner so won't last as long. But do be aware of one potential drawback with DIY ceramic coatings. Unless you thoroughly prepare the paintwork first, you will effectively seal in any imperfections, leaving them visible and very difficult to remove until the coating wears off. That's why a professional treatment will remove contaminants with a clay bar, then polish it with a machine to free the surface from any blemishes before the ceramic coat is applied. That's what you're paying for.
Bear in mind that if a scratch or contaminant has gone through the clear coat and the base coat, the only solution is touch-up paint; if you can see the light-coloured primer, no amount of polishing will restore the finish. Touch-up paint to match the original is widely available and often in pen form, which many people find much easier to use than a brush or spray. If you are getting ready to hand back a leased car with a peppering of stone chips on the bumper, a mobile chip-painting service might be less expensive than the lease company's penalties.
Modern car paints do chip and scratch more easily than the finishes of the 1970s and 1980s. That's because carmakers switched from largely petroleum-based paints to water-based paints, which are softer, for environmental and health reasons. That means modern paintwork more easily accumulates swirl marks — visible as circular fine lines if you look at the paint at an angle under sunlight or a bright light.
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Car paint consists of three layers: a primer, a coloured base coat, then a clear coat to give shine and to protect the coloured base coat from fading in sunlight or being damaged by contaminants such as bird droppings, tree sap or traffic fumes.
The clear coat is usually between 50 and 100 microns thick and is tougher than the coloured base coat, but 'tough' is relative. The international standard for defining paint hardness is to determine what grade of pencil will scratch it. Pencil grades go from 9B as the softest, through HB, typical for writing, up to 9H, which only gives a faint line, but stays sharp for ages. The clear coat on most cars is about 3H to 4H, meaning a 5H pencil used on the surface will leave a scratch.
The trouble is, this is softer than most of the tiny particles of dust, grit or brake dust that make cars dirty. As the car is washed, these particles tend to cause tiny scratches, which is why using a specialised car shampoo containing a lubricant is important. An automatic carwash should rinse the brushes after each wash to get rid of dirt particles, but even if the brushes start out completely clean, dirt picked up from your car can stay in the brushes and inflict tiny swirl marks on the paint. A good handwash will use thoroughly rinsed cloths for each car, but again, residual particles or dirt picked up from your car can leave swirl marks and eventually a duller finish on the paint.
There are two academic papers supposedly proving that handwashing causes more damage than an automatic car wash, but bear in mind that one was sponsored by the International Carwash Association, supporters of carwash machines, and both compare carwash machines to DIY handwashing, not a professional or two-bucket handwash.Tim Shallcross, independent expert
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