Paint Decontamination


Decontaminating a car’s paint finish is an often overlooked detailing step yet very necessary to achieving a flawless finish. ‘Step 1’ in the exterior automotive detailing process consists of a thorough initial washing (preferably using the two-bucket wash method) with a product that will remove any existing sacrificial protection (any prior existing wax or sealant) plus any basic paint contamination (dirt, dust, grime, etc.). The easiest and quickest way to remove any existing wax, sealant, grime, etc. is to use a product such as Dawn Dishwashing Soap. I don’t recommend using this soap too often as it may prove to be too harsh for rubber/plastic – but once or twice a year is fine. A dedicated car wash soap is your next best option – a product such as P21S Total Auto Wash will produce a very clean surface. Once you wash (and dry) the car, and prior to polishing to remove swirls, marring, cob webbing, scratches, oxidation, etc., it is very important to prepare the paint through a ‘decontamination’ step beyond what the washing process did. With this said, ‘Paint Decontamination’ is ‘Step 2’ in the exterior automotive detailing process and that is what this section is about.

What is Paint Contamination?

Paint contamination consists of any airborne chemical compounds, ferrous (iron containing) particles, adhesives, industrial fallout, rail dust, acid rain, bird droppings, road tar, grime, tree sap, bugs, water spots, brake dust, road salt, oil, paint overspray, etc. either on or embedded in the paint surface. Some of these contaminants, particularly fresh contaminants, may come off the paint surface with the initial washing. Some other contaminants, however, will actually penetrate and/or bond to the paint and, over time, eat into the clear coat thereby causing pitting, premature clear coat failure, and/or overall accelerated degradation of the paint.

After washing and drying the car, the absolute simplest way to determine if the paint is contaminated is to perform a “bag test” (see video below). Take a Ziploc bag and place it over your hand. Now rub very lightly across the freshly washed car’s paint surface – if you feel any little snags or bumps then contaminants are bonded to the surface or embedded in the paint. In addition to the bag test, the visual appearance of the paint may also offer clues: does it have small yellow stains, water marks, black-colored spots, bug residue, bird droppings, tree sap, etc? If so, then the paint surface is contaminated and, if the contaminants are not removed, corrosion will eventually occur. In addition, removing the contaminants will leave the cleanest surface possible prior to polishing.

Automotive Detailing Clay

The next level of paint decontamination (and most cost effective) after washing is achieved through the use of ‘detailing clay’ through a process known as ‘claying’.

Detailing clay is designed to remove above surface bonded contaminants on paint, glass, fiberglass, and metal. While claying is excellent at removing above surface bonded contaminants, and is an essential step in the detailing process, it is often a foreign process to many car enthusiasts and, to others it’s considered non essential. Over the years, however, claying has proven itself time and time again. Today, detailing clay can even be found in your local auto parts store. Claying will add a new dimension to your detailing portfolio and will enhance the overall finish of the paint.

Keep in mind that even new cars are subject to paint contamination. It was once thought that detailing clay shouldn’t be used on brand new (show room) cars. This, however, is not the case! New cars have a considerable amount of bonded contaminants – simply transporting a new car to the show room floor via train or truck will undoubtedly leave brake dust and/or rail dust contaminants that washing will not remove. In addition, new cars that have been sitting on car dealership lots for even a few weeks can accumulate contamination from acid rain and/or industrial fall out.

It is important to understand that the use of automotive detailing clay does not replace polishing…after claying you will still need to remove embedded contaminants using a paint cleanser and then polish the paint in order to remove defects (and then protect it with a sealant or wax). Clay contains mild abrasives designed to remove above surface bonded contaminants. Some argue that polishing or compounding will do the same thing as claying but that is not the case. Polishing or compounding will not necessarily remove bonded or embedded surface contaminates and in some cases will just ‘round-off’ the edges of such contaminants thereby leaving them to eventually corrode the paint. Claying will remove the surface contaminants and a percentage of the embedded contaminants. Polishing and claying are very different processes.

Types of Clay

Shopping for detailing clay might leave you confused as there are different grades of clay currently available and a large number of vendors sell detailing clay under their own name. As far as types of clay, there are essentially three types. One is a ‘mild’ grade detailing clay designed for claying a vehicle once or twice a year. The other is ‘fine’ grade detailing clay that removes everything the medium clay removes but is gentle enough to use monthly or as needed for spot cleaning – essentially a ‘maintenance’ clay (this type of clay is generally more costly). Finally, there is an ‘agressive’ clay designed to remove the most stubborn contaminants. There are also a number of ‘alternatives’ to clay on the market – I have not used nor see a use for these products and, hence, can not recommend them. A mild clay will often suffice for most situations.

As far as vendors go…buying from a reputable vendor is your best choice (Meguiar’s, Mothers, Pinnacle, Clay Magic, Griots, etc.). The simply fact is that all the US Patent rights for detailing clay are held by the same company, Auto Wax Company Inc. The leading detailing companies get their clay either from Japan (Shinyo Chemical Co., Joybond) or from a US licensed manufacturer. So, don’t break your head trying to find the ‘best’ clay. Meguiar’s Mirror Glaze Professional Detailing Clay (mild) will do just fine (or any clay by Mothers or Clay Magic that you can find at your local auto parts store).

Clay from any reputable detailing vendor will suffice.

Independent of the type of clay you decide to use, claying requires the use of a lubricant to reduce surface marring during the claying process. I have noticed that a lot of vendors advertise their clay as being non-abrasive but, as shown below, this is simply not the case!! If the clay is used as the manufacturer suggests, it should not mar the paint BUT clay is an abrasive product. Most, if not all, clay consists of calcium carbonate, polybutylene, and silica. Calcium carbonate and silica are inherently abrasive. Below I demonstrate the abrasiveness of detailing clay by performing a CD test. Two comments: First, the surface of a CD is more delicate than the surface of a car and second, the results are shown for the situation where a lubricant is not in use. The purpose of this demonstration is simply to show that clay is indeed abrasive and utmost care should be taken when using it. Keep in mind that there are a number of variables that one must consider when using clay such as clay agressiveness, quality of lubrication, downward pressure, number of passes over the same spot, etc. In some cases, you may be left with a ‘clay haze’ after claying…the ‘haze’ actually consists of very dense, shallow scratches in the paint surface. This ‘haze’ will easily be removed via the polishing step. Most over the counter clay products, e.g. from Meguiar’s, Mothers, Clay Magic, etc. come with a lubricant.

Detailing clay is inherently abrasive. Performing a CD test with a new CD (A) and some detailing clay (B) yields scratches on the surface of the CD (C)-(D).

Claying a Car: Application

Detailing clay, while abrasive, is not meant to abrade your paint surface but is meant to abrade or shear off any above surface bonded contaminants. As mentioned above, detailing clay needs to be used with proper lubrication. It is important to note that you may have to remove minor surface marring caused by the claying process if the clay is not used properly. This is not really a big deal because you will/should follow the claying process with a polishing step anyway. Understanding how the claying process works, however, will ensure that minimal surface marring occurs.

The claying method ensures that the clay glides along the surface of the paint on a thin film of lubrication. The lubrication provides a safety barrier between the clay and the paint while it removes the above-surface-bonded contaminants. Without lubrication the clay will certainly mar the paint surface (akin to wet sanding) and grab to the surface. By the way, there is nothing magical about the lubrication – any quick detailer will suffice – even though you will find a plethora of dedicated ‘clay’ lubricants on the market, a detailer such as Meguiar’s Quik Detailer works well as does Optimum No Rinse mixed as a detailing solution.

The claying method:

  1. Select the appropriate abrasiveness of detailer’s clay…I recommend mild as it works well (e.g., Meguiar’s).
  2. Divide the clay bar into several equal pieces and knead into a ball to warm it – you will need enough clay (30-40 grams) such that when you flatten it out into a circle, there will be enough to fit onto two or three fingers.

    A) Cut about 30-40 grams of clay from the clay bar, B) roll it into a ball and knead it to warm it, and C) flatten it so that it covers 2-3 fingers.

  3. Now liberally spray a 2-foot by 2-foot section of your car with a lubricant…make it good and wet – don’t skimp. The key to claying is to use plenty of the lubricant so the clay bar glides over the paint surface.
  4. Take the clay, and with two to three fingers on top of it and, using very light hand pressure, glide it back and forth across the area you just sprayed. You may hear a slight noise and feel some resistance; this is normal and will dissipate as the contaminants are removed. Make sure you keep the surface wet and continue to spray as needed.
  5. After you complete one section, wipe it dry with a quality microfiber towel and then move on to the next section and repeat the process.
  6. Make sure that you inspect the clay after each section and knead /fold as necessary to provide as clean a surface as possible.
  7. When you complete the whole car, wash it thoroughly and dry the vehicle. The surface is now ready for a paint cleansing step, a polishing step, or application of a wax or sealant.

If you drop the clay on the ground, discard it!! Otherwise, you will cause scratches in the paint!!


Paint Cleanser

After you finish claying, the surface of your paint will have a glassy smooth finish. Claying is intended to remove above surface bonded contaminants. Embedded contaminants, however, are not usually removed during the claying process. To remove embedded contaminants you need to use a paint cleanser. There are a number of paint cleansers on the market and they will do a good job at removing embedded contaminants. Following the paint cleanser step, you can either proceed directly to your Last Step Product (LSP), i.e. wax or sealant, or you can proceed to polishing the paint. If your paint has defects, i.e. swirling, scratches, etc., then you will need to polish it. Otherwise, put on your LSP and enjoy!


  • Detailer’s clay can also be used on glass surfaces to remove heavy road film, bug deposits and surface water spots and on wheel surfaces (although not recommended on wheels that do not have a clear coat or powder coat finish).
  • If the clay streaks on the paint, apply more lubricant – it is better to over lubricate then to have the clay streak (and potentially mar the paint).
  • Claying needs to be done during optimal temperatures. If you try to clay a car when the surface is too cold (<50 degrees F), the clay will be hard and you will not be able to get a nice surface. If you try to clay when it is too (>90 degrees F) the lubricant will dry too quickly and your chances of marring the surface increase. Keep in mind that the paint surface of a car gets extremely hot when it is in the sun, try to move to the shade or indoor if you need to clay when it is hot.
  • Clay can be re-used depending on the level of paint contamination. You can probably get 2-3 uses for situations where the paint contamination is not too bad – use your best judgment, it is better to err on the side of caution.
  • When not in use, detailing clay can be stored in a cool, dry place, in a plastic bag or its original container. Simply mist the clay with a quick detailer and place it in the storage container it came with or a plastic bag.
  • I don’t recommend you clay the same car more than twice a year unless it is exposed to extreme contamination. Keep in mind that it will probably take 1-2 hours on average to clay a car.
  • There are other ways to decontaminate a car’s paint surface aside from claying. Claying will remove a large number of contaminants but may not completely remove all embedded contaminants. To remove paint contamination beyond what washing or claying can achieve, you will have to use a chemical method. Finish Kare has developed a Paint Decontamination System that is designed to remove surface and sub-surface (embedded) contaminants without damaging your paint finish. I have not personally used their system and, hence, can not recommend it (but I have read good things about it).