Decontamination Guide

Decontamination Guide

Your vehicle is constantly being attacked. “By what?” you say. “My car is parked, minding its own business.” Gravity is not a friend of your vehicle’s finish. Everyday your car is exposed to the elements, air-borne nasties are landing on your car; fallout, overspray, iron (ferrous) metal, bugs, tar, road film, tree sap and others, bonding to the paintwork and leaving it looking dull and feeling like sand paper. We refer to these nasties as Contaminants and the process of this occurring as Contamination.

Contamination comes in various forms and classed into a few main categories.
Iron (ferrous Oxide) fallout
Metal shavings from brakes and wheels of cars, trucks, buses, trams and trains fly of the off while still red hot and embed themselves into your soft paintwork. When these shavings next see rain, condensation or moisture they rust and turn orange, which is why you can sometimes see little orange spots on light coloured vehicles.

Tree Sap
The heat can cause sap from leaves to drip onto your vehicle. In the form of a clear resin, sap can be extremely sticky and in thinner form cover your entire vehicle and prevent it for beading or even sheeting water.

Tar, Bitumen & Road Film
Tar and Bitumen are used in the roads we drive on. When roads are being laid or have been freshly laid, tar and bitumen is pulled up by tyres and can be then flicked off onto your vehicle. A sticky black/brown substance can be a pain to remove from paintwork, wheels, wheel arches and undercarriage.
Overspray & Fallout
Mostly airborne, travelling for 10’s of kilometres, overspray and pollution fallout can find its way onto your vehicle even if you have been nowhere near the source. Some of this can be directly from the spray gun during painting of buildings, structures, cars and furniture. Manufacturing factories where exhaust filters are blocked or not checked regularly also may release overspray into the environment.
Pollution & Film Build Up
Most common on every car, this is where everyday road grime bond with minerals in the rain water and pollution in air to create a dull coating over your vehicle.

Removing Contamination (Decontamination)
“That’s just great” I hear your saying as you read this. “All these things stuck on my car”. Now that we know the different types of contamination we can find the most suitable way to remove them.
How do we know if we have contamination on the vehicle?

There are a few easy ways to tell if you have contamination on your vehicle’s surface. I say Vehicle rather than paint, because our friend Gravity doesn’t discriminate and your paint, glass even plastic trim could be covered.

First way is by gently gliding your fingertips over a clean, dry surface. Here you will be able to feel anything bonded to it. To help with this, a method we have recommended over the years is to use a clear plastic freezer bag. Sounds Crazy? By placing your hand inside the freezer bag and then gliding your fingers over the surface, your sense of touch is heightened, allowing you to feel contaminants bonded to paintwork, which you were not able to notice prior.

Next way is to visually examine the surface. On a light coloured vehicle you may notice tiny orange specks on the paintwork, which are signs of iron fallout. Tar you will notice as a sticky black drop. Tree Sap as a clear spot & bugs.... well we know what they are. On both light and dark coloured vehicles you may notice a dulling to your finish, almost like a thin coating of grime. You mostly notice how dull this is once you have removed the contamination from a small adjoining section. 

Let’s Get Rid of it (The Decontamination Process)
We have covered what contamination is, the different types and how to work out if you have it on your vehicle. Now it’s time to get rid of it.
This is the Decontamination Process, sometimes referred to as decon for short. Here our goal is to remove everything from the surface.
There are a few ways to tackle this problem, Mechanically and Chemically.

Mechanical Decontamination is the process of gently massaging a polymer based resin, over the surface of the vehicle, to shave off contaminants. This polymer based resin is known as a clay bar, detailing clay or overspray clay and can be found in different grades from Fine to Heavy, chosen depending on the severity of the contamination. These are examples;

We use a lubricant (clay lubricant) during this process to allow the clay bar to glide over surface in an attempt to minimise any marring resulting from the abrasives contained in the clay bar.

‘Claying’ will remove the majority of contaminants from the surface however there are some that respond better to chemical treatments used in conjunction with the claying step. For example we know from our earlier description that Iron fallout embeds into the paint. Claying shaves contaminants off the surface only. Therefore there is still some fallout in the paint. Here a chemical treatment can be used to open the pores of the paint, dissolve the contaminant and release it. This is a good step to add to the claying process.

The ‘Clay Bar’ is the most common form of mechanical decontamination, yet there are a few others. The latest generation of ‘clay bars’ see other forms of media such as MF cloths, foam pads and buffing pads coated with a thin layer of polymer resin. By coating a different form the ‘claying process’ can be speeded up. These types of ‘claying’ media include;


Chemical decontamination allows for elements bonded to the surface to be removed without an abrasive component. The following is a list of products that can be used on various contaminants.
Tar & Tree Sap

Iron (ferrous oxide)

Pollution & Traffic Film

Best of Both Worlds
Everyone loves to save time, especially when you can get the same great result. Concours Car Care have a released a product called Purify that is both; clay lubricant, iron remover and degreaser all in one. The active ingredients in Purify both attack iron and ferrous metal contamination in paintwork and remove any build of waxes or sealants, leaving the paintwork with a hydrophilic surface (one that does not bead water), indicating everything has been striped. All at the same time allowing the clay to glide over the surface to reduce marring in the process.

How to Clay the Vehicle
Clay bars generally are two sizes 100g or 200g. We want to work with about 50 grams at a time, so cut your new clay bar in to size and place the rest back for storage.
With the palm of your hand, flatten out the clay bar to round disk, approximately 9-10cm in diameter or the size of your palm.

Place the clay disk in the palm of your hand, lying under your finger tips. Try to avoid placing your finger tips on the clay disk as the pressure can be uneven and cause additional scratching to the finish.

Spray the clay generously with a strong mist of clay lubricant.

Place a Microfibre Cloth on the paint surface as a reference to the size of the area to be clayed. Spray a generous amount of clay lubricant on the surface after removing the Microfibre cloth.

Place the clay disk on the surface and with light pressure (the weight of you hand) glide (almost pushing) the clay over the surface in the area prepared with your clay lubricant. Moving forwards in an up and down snaking motion, then side to side to ensure the entire area has been covered.


You may feel the clay gripping on the surface. This is ok, it’s the clay making its way through the contaminants.

Once you feel no resistance in the clay bar, stop claying and wipe down the surface with a clean microfibre cloth. Inspect the surface by both visually and by touch to ensure all contaminants have been removed.

After each section, inspect your clay disk. If you find there is a build up of contaminants on the surface, kneed the clay disk into a ball and flatten out again. This will redistribute the clay and allow for a fresh surface to continue with.

Resize another area with a microfibre cloth, prepare both this area and your clay disk with lubricant and continue claying.

Once finished, return the clay into the container for storage.

Note: If your clay is dropped on the floor please do not continue to use it as it will have picked up an debris. You may re kneed the clay or even slice of the area that made contact with the area but at your our risk of scratching and marring the finish.