How To Polish Paint Part II: How To Evaluate Your Paint, and Understanding Paint Systems

Evaluate Your Car's Paint for Polishing

How do you properly evaluate your car's paint surface for polishing? Most professionals (painters and detailers) will tell you that paint evaluation is a combination of seeing and feeling. What you're looking for is a surface that's flat like glass. What you want to feel is a silky, smooth surface with very little resistance.

When perfectly polished, paint looks like a reflecting pool and feels like fine cashmere. Want to see what you're missing? If you're looking for imperfections, use good fluorescent lighting. Incandescent lighting and sunlight do not show surface imperfections as well as good fluorescent light. Feel for surface imperfections and roughness with your fingertips.

Use a light touch to gently glide your fingers over the paint surface. You'll be amazed at how much you will feel once you have trained your fingertips. You may be wondering just how much of what you see and feel on your paint should be polished away versus cleaned? This is a greatly debated question. Not too many years ago, polishing would have been the correct answer.

Today we have more choices. When possible, I recommend paint cleaning before paint polishing. The best tool for removing heavy paint contamination is detailing clay. If your paint is clean and free of visible defects, is it necessary to polish before waxing? This is another question for great debate, and there are two basic schools of thought.

One methodology proposes that polishing is not necessary, because your wax should provide the final finish. The second methodology proposes that polishing creates the level of gloss, and waxing increases depth and liquidity of the surface. I propose that a combination of the two is correct. I believe that polishing should be used to repair and perfect paint, and waxes should be used to protect paint and create a deep, high-gloss finish.

Evaluate Paint Thickness Before Polishing

If you plan to sand or compound a vehicle's paint to repair or perfect the surface, you should measure the thickness of the paint first. To do so, you will need a paint thickness gauge. There are two basic types. An electronic (sonic) meter provides the most precise measurement of coating thickness.

These meters are too expensive for most enthusiasts, but should be part of every professional's tool kit. A less costly tool is the magnetic thickness indicator, which can measure coating thickness to within .001 inch (1 mil). If paint thickness is less than 6 to 8 mil, it's not safe to wet-sand or compound. If paint thickness is less than 4 or 5 mil, it is not safe to polish with a material higher than grade 2 on the polish chart.

Understand Your Car's Paint Before Polishing

Throw away everything Dad ever taught you about polishing your car, because the rules have changed dramatically in the past 10 years. There are three important changes that have made a significant impact on paint polishing. First, modern car paint systems are no longer petroleum-based coatings. All new car paint systems are water-based urethanes.

Equally important, almost all cars rolling off the assembly line today have a multistage paint that includes a top clear coat. Second, production of man-made micro abrasives has been perfected. Abrasive manufacturers are making micro abrasives engineered to an exact size and shape to produce a consistent cut. Third, the microfiber cloth industry began producing cloth materials specifically for polishing applications.

Traditional cotton terry cloth is not only yesterday's rag, it is also many times more likely to scratch modern paint finishes than a quality microfiber polishing cloth. The high-tech paint systems on the modern automobile differ from their predecessors in structure and in the care they require. In general terms, the finish layer on all cars of the past was a pigmented, oil-base, solid-body paint. When polishing these conventional finishes, you work directly on the layer of paint that gives a car its color.

The modern car paint finish has a primer layer, color layer and a clear top coat layer for added beauty and protection. Although the modern clearcoat paint system is more tolerant of everyday problems than conventional finishes of the past, it requires a little more knowledge for proper care. Understanding your car's clearcoat system is necessary to provide proper care and to facilitate repairs.

All clearcoat systems are basically the same. A clearcoat system consists of one or more primer layers, a flat color layer and a glossy, clear top layer. The primer is a corrosion inhibitor and a bonding agent for the bare metal and the color layer. It prevents corrosion and provides a stable substrate for the color and clear coats. The color layer is applied to the primer and is typically very thin. Its only purpose is to provide color. The clearcoat is two to three times the thickness of the color layer, adding to the appearance of paint depth and offering additional protection.

Many luxury car manufacturers also use ultraviolet-light-blocking technology in their clearcoat systems for protection against sun fading. A clearcoat finish is somewhat forgiving. Faults in a clearcoat finish are easily corrected compared to faults in solid pigmented finishes, such as enamel, acrylic or lacquer. Scuffs and scratches in pigmented paint layers are challenging to correct, because the top layer contains the color. This is especially true if the scratch penetrates the color layer into the primer layer.

In a clearcoat system, most minor scratches and scuffs never reach the color or primer layer. In these cases, a quick polishing is all that's needed to repair a minor blemish. How can you tell if your car has a conventional finish or a clearcoat finish? It isn't always easy to tell. One test is to gently rub an out-of-sight place on the finish with a polish or fine compound. If the paint color comes off on your polishing cloth, you have a conventional finish. Polishing on a clearcoat finish should not reveal any color on your polishing cloth.