In this month’s column, I will continue with a discussion of the information needed to successfully complete the “Prep Wash/Wash Bay” portion of the detailing certification exams offered by the International Detailing Association.

The IDA offers it’s Certified Detailer program to both members of the association as well as non-members. The program currently consists of 10 tests that assess the taker’s background knowledge of detailing. This month’s column is one in an on-again-off-again series that is designed to present a study guide for those who are interested in taking the tests. Get more information or sign up for the tests at

In last month’s column, we began the discussion by defining the “prep wash” as a procedure that prepares the vehicle for exterior detailing. The exact prep wash procedure used depends on many factors, but, in general, we will wash the dirtiest parts of the vehicle first. If the engine bay is included in the package, it is washed first. Then the other dirty parts like wheel areas, doorjambs, rocker panels, and front exposure is washed and rinsed. Finally, the main body of the car is washed.

After rinsing the entire vehicle, it is dried using the technician’s choice among several available drying options.


Even after a thorough wash, the paint surface of a vehicle typically feels rough or gritty as you pass your hand across the surface. This is where the concept of “claying” comes in. Before the advent of traditional clay bars and newer “clay” media, surface contamination could only be removed with buffing and polishing, sometimes requiring multiple steps. But now it is relatively simple to make the paint surface feel smooth to the touch and ready to accept paint protection like wax or sealant.

Understand that the purpose of “claying” a vehicle is solely to remove contamination that is sitting on the surface of the paint. Claying leaves the paint surface smooth to the touch. Claying will not remove scratches, it will not polish the paint, it will not completely remove oxidation, and it does nothing to protect the paint. On the other hand, I believe that, for vehicle paint, claying and protection go hand-in-hand. I will never clay a vehicle without at least waxing it afterwards. And, I will never wax, seal, or coat vehicle paint without at least claying it first.

Traditional detailer’s clay is a malleable plastic resin that comes in a rectangular block. Typically, the technician will break off about a third of the block and shape it into a flat pancake for use on the paint. Traditional clay bars are very effective at removing surface contamination, but, if dropped on the ground, must be thrown away due to the possibility of collecting grit that could scratch the vehicle paint with continued use. Hence, again, using only one-third of the bar at a time.

Newer “clay” technology includes the use of polymerized rubber, which is applied in a thin layer to one side of a microfiber towel, a mitt, or a polishing disc. Using appropriate lubrication — car wash shampoo or spray wax — these devices are rubbed across the paint surface, picking up surface contamination in the same way as traditional clay bars. The true advantage of clay media over clay bars is that if dropped on the ground, clay media can simply be washed off before continuing to use.

The decision to use traditional clay bars or clay media is one of personal preference, although clay bars tend to be more effective for heavy contamination or overspray.


Many technicians prefer to perform the clay procedure during the prep wash and in the prep wash bay. Specifically, after finishing up the wash and final rinse, the technician makes up a new bucket of car wash shampoo and uses that, transferred to the car with a wash mitt, as the lubricant for the clay or clay media. Environmental fallout is a broad term that describes any contamination on the surface of the paint that does not come off with normal washing. It’s what makes the paint surface feel “gritty” or rough, even after thorough washing and drying.

When the surface contaminant is paint overspray, it is sometimes better to perform the removal process after the car has been washed and dried. This allows for easier monitoring of the working area, which can ensure that all of the contamination is removed, one section at a time.

Another example of surface contamination is industrial fallout, sometimes called “rail dust” or ferrous oxide deposits, which is basically tiny pieces of iron that are stuck to the paint surface. Light concentrations of industrial fallout can be removed with detailer’s clay or surface prep towel. Nonetheless, it is important to know that clay may not remove all of the iron deposit, simply breaking off the top and leaving behind a portion of the deposit embedded in the paint.

Heavier concentrations of industrial fallout will likely require a more aggressive approach. In this case it may be necessary to use a specialized iron removing product and procedure. One option is sulfur-based iron removers that can also help loosen the embedded iron particles. These products are sprayed across the vehicle surface and allowed to dwell, resulting in a purple residue when the product comes into contact with iron. Some technicians don’t like this type of chemical because of its strong odor — sulfur smells somewhat like rotten eggs — and worry that the odor could linger on a customer’s driveway.

Another, more aggressive approach to removing iron deposits is to use an acid-based, iron-removing chemical or oxalic acid washing procedures in the wash bay. This is sometimes referred to as “acid-washing” a car. This is a specialized procedure that requires safety gear, a controlled environment, and an extra wash step to neutralize the acidic product once it has been applied and rinsed.

It is critical here to point out it is absolutely inappropriate to use “wheel acid” for acid-washing the overall vehicle. Wheel acid or acid wheel cleaners use a specific type of acid that is safe only for use on wheels. For removing heavy concentrations of iron oxide, use only chemicals labelled specifically for use on the main body of the vehicle.

Whether you use the sulfur-based or acid-based specialized chemical decontamination procedure, finish up by using detailer’s clay or other clay media along with a new batch of car wash shampoo to remove any leftover surface contamination. Then perform a final rinse.

Sometimes the windows and paint surface may have water spots or water etching. Water spots, which are the leftover water-borne minerals after the water drop dries, will typically be removed by clay procedures. Water etches, on the other hand, are actually in the paint or glass surface, and will not go away with washing or claying.


Sometimes we find ourselves in a situation in which water is not available, or allowing rinse water and chemicals on the ground is simply not an option. In this case, the technician can rely on non- or low-water methods.

One option is to use a waterless wash product, which involves spraying the product directly on the vehicle and gently wiping it with a clean microfiber towel. The waterless product typically is high in lubricating and emulsifying chemicals that capture light surface dirt and help lift it from the surface to help minimizing the inevitable scratching that will occur when wiping a dirty paint surface.

Another option is to use a bucket of water infused with so-called “no-rinse” style washing chemicals. These chemicals, like the waterless kind, have lots of lubricating and emulsifying ingredients that allow the user to “wash” the vehicle paint with a damp chamois, followed by drying towels.

The advantage of this type of vehicle washing is, of course, greatly reduced water use, and virtually no water or chemical on the ground.

The disadvantage is that some micro-scratching will occur, and typically lots of towels are required!


The prep wash should be distinguished from the “full-service wash.” A full-service wash is just that: a car wash without any surface contamination removal, paint correction, or waxing. Many of the stronger chemicals used in the prep wash will not be used for a full-service wash because these stronger chemicals can strip away the protective chemicals (like waxes and sealants) that may be on the vehicle.

Instead, use a car wash shampoo that contains “wax.” This will give the car a few days of protection as well as add to the gloss. Although using “car wash shampoo with wax” is not a substitute for the multi-month protection offered by standard waxing procedures, it does tend to leave a better look than straight car shampoo.


The prep wash, at first glance, seems like it should be a fairly straightforward process. But as you can see by this discussion, there are actually several issues and variables that make it a complex project. The most important thing to accomplish in regard to the prep wash is to set up standard operating procedures so that it can be accomplished in the shortest amount of time possible with the best result.

Prentice St. Clair is an International Detailing Association Recognized Trainer and Certified Detailer. As the president of Detail in Progress Inc., he has been providing training and consulting to car washes and detail shops since 1999. He is available at (619) 701-1100 or