Contaminants are made up of lots of particles which are harmful to your paint and can be from tree sap, tar from the roads, industrial fallout, iron filings from the train tracks (used to deliver new cars). These dirt/contaminated particles are what make your car look dirty, dull and feeling rough.
Keeping your car regularly washed can help with the removal of these particles and is important to do so to maintain a high quality finish. However, alot of these contaminants cannot be removed by washing alone which is why even after washing your car it can look shiny but actually on closer inspection feel rough to the touch.
How To Test For Paint Contamination
To determine whether or not your cars paintwork has these contaminants bonded to it, thoroughly wash your vehicle and run your fingers over the wet panels. Good condition paint should feel perfectly smooth, like a sheet of glass.
If you cannot feel these contaminants very well, try the same method but putting your hand in a sandwich bag first to help amplify the feeling. If your paint feels rough or gritty then your paint contains bonded contaminants which should be removed.
Types Of Paint Contaminants
Now that you have hopefully (or hopefully not!) identified the contaminants on your paint it is necessary to identify what type of contaminants they are in order to successfully and safely remove them. Contaminants visible to the naked eye are usually made up of organic materials and as such come in the form of tar, tree sap, honeydew and insect remains.
Tar spots are probably the most common contaminants found on the lower third of vehicles due to the tyres picking up tar from freshly laid roads and flicking it over your bodywork. This is more of a problem in the summer due to the flexibility of tar and bituminous products, becoming softer and easier to pick up.
Honeydew is another problem most commonly found in the summer due to the pollination and high insect population. Insect remains/bug splatter are another problem amplified by the insect population in the summer months but can become very hard to remove and often require polishing due to the acidic nature of them and therefore their corrosive properties.
Inorganic items include the industrial and commercial activities such as iron filings, railway dust, brake dust, industrial fallout, paint over-spray and many other sources. The problem with these inorganic items over the organic items are the way they can bond both physically and chemically.
They accumulate over time until you can physically feel them, in the form of rough paint, and see them, in the form of poor surface finish and lack of water beading/sheeting due to the contaminated layers of protection. The other problem with these contaminants is their diminishing properties such that over time they oxidise and corrode, harming the paint that they have embedded themselves in causing etching and discolouration which will need rectifying through polishing.
How To Remove Contamination
The safe removal of bonded surface contamination requires special techniques. We have already established that normal washing doesn’t remove them.
Stronger all purpose exterior cleaners may partially remove some of them when used at maximum strength, but even then would struggle to fully dissolve larger organic particles and would certainly not remove many inorganic particles, as they are largely insoluble.
Aggressive polishing would almost certainly remove such contamination, but is a far from ideal solution because bonded contaminants often need to be removed two to three times a year and aggressive polishing should not be done anywhere near as often as this.
What is really required then is a method that employs products capable of removing such contaminants without affecting underlying painted surfaces. Fortunately such products exist, and comprise tar removers and detailing clay.
The clay used in detailing clay isn’t really clay at all, but a mixture of a soft plastic resin (polybutene) and various grades of abrasive particles. Think of it in this way; the soft plastic resin is effectively an applicator pad, which enables you to move abrasive particles over your paint using consistent force and pressure.
Bonded surface contaminants sit above the surface of the paint, they are subject to greater abrasive forces than the surrounding surfaces when a clay bar is rubbed over them.
As a result, they are abraded away and removed by the clay bar. You may be questioning at this point why the abrasives in the clay don’t affect the surrounding paint? The answer is they would, if they were allowed to. You have to stop them from doing so, by using a suitable lubricant.
Clay lubricants come in a variety of guises, but most are effectively quick detailing products. These spray on, wipe off products contain lubricating oils (which enable dust and grime to be wiped off exterior surfaces safely without inflicting damage to the underlying surfaces) and are well suited to use with detailing clay.
In addition, heavier duty waterless wash products are also ideal in this respect, as they contain an even greater concentration of lubricating oils.
If you do not have any of these products, a very rich suds mixture made up using a normal shampoo can sometimes suffice, but do note that sometimes such solutions can partially dissolve detailing clay and make it messy to work with.
At this stage you may be asking why not simply use detailing clay to remove all bonded surface contaminants; why were tar removers mentioned above?
The answer is that detailing clay can be used to remove all of the contaminant types mentioned above, but a potential problem arises in that bonded organic contaminants generally comprise much larger particulates than bonded inorganic contaminants, and therefore have greater potential to cause surface marring at the interface between the clay bar and the paint as the clay bar is moved around.
Given that bonded organic contaminants are usually highly soluble in paint solvents, it makes far more sense to remove them chemically rather than physically, as dissolving them and then rinsing them away virtually eliminates the risk of causing marring.
It should be noted that surfaces treated with tar removers will still need to be clayed afterwards, as inorganic particulates are not usually soluble, and so are rarely removed by chemical means alone.
Thus, often a two stage decontamination process is required to fully clean paint, comprising an initial chemical treatment to safely and effectively remove bonded organic contaminants (tar removers also remove honeydew and bug splatter extremely effectively), followed by a physical treatment with a clay bar to safely and effectively remove bonded inorganic contaminants.
The method for using tar removers requires no real explanation as most simply spray on and rinse off, but the use of detailing clay is more complicated, so a step by step guide is therefore provided in the next section of this guide.
