A clean surface will have a nice, shiny appearance free of any cracks, crevices, scratches and major pores. These “perfect” surfaces will reflect most of the incoming light in one direction and will not allow industrial fallouts — acid rain and other contaminants — to penetrate from the outside layer (clear coat) to lower ones. Thus, the surface provides protection for the rest of the vehicle’s paint.
However, if the clear coat has contaminants, build-ups or scratches and other mechanical or chemical damages, it will absorb and scatter the incoming light into multiple directions, resulting in a dull/matte look. In addition, this surface will not provide extensive protection, since the imperfections will invite contaminants to penetrate deeper into underlying layers of the clear coat (base coat, primer) and eventually to reach the metal body causing rusting.
A look at peaks and valleys
Perfect, smooth surfaces have the least possible surface area, whereas imperfect, rough surfaces possess larger surface area encouraging damaging chemical reactions to take place at a higher rate.
From a physical point of view, polishing and waxing reduce the surface area by leveling, i.e. moving toward the perfectly smooth surface. Polishing cuts off “peaks,” waxing fills up “valleys.” The result is a smooth, glossy surface.
If the peaks are not too high and the valleys are not too deep (slightly contaminated and damaged surface), either cleaning and polishing or cleaning and waxing could create a smooth surface.
Newer surfaces with minimal damage do not need extensive polishing or waxing. A good cleaning followed by a quick polishing (buffing) or the application of a spray-on type wax (express wax) either manually or automatically, online or after the carwash, can save lots of labor and generate extra income to detail shops and carwashes.
For more damaged surfaces, a thorough cleaning and labor-intensive polishing and waxing are combined at many detail shops for a restorative detail service. After surface evaluation, cleaning should always be the first step to remove all the contaminants above and beneath the surface. Hard to remove deposits and embedded pollutants might need special non-abrasive cleaners (e.g. clays), deep cleaners (with very fine abrasives) and some mechanical force.
Usually, polishing can cut deeper through the surface than the lowest point of the damaged layer. This will create a new surface but will not provide protection. Too intensive, frequent or uneven polishing can even damage the thin clear coat layer. If the clear coat is cut through and the base coat is reached, shine and protection cannot be restored without repainting.
Waxing on the other hand, should fill up more than the depth of the valleys to create an additional protective layer all over the surface. These protective layers are temporary though, and will be worn off. If waxing takes place on a cleaned, polished surface, a wax layer with uniform thickness and an even surface protection can be achieved which can last longer. Express waxing can be a solution for a more frequent but less expensive maintenance care for newer cars or older ones with well maintained finishes.
Polishes and waxes: How to choose the right product
There are multiple products on the market and multiple definitions for these chemicals. In general, polishes contain some cleaners and abrasives to remove contaminants and the high points of surfaces (“shaving off” damaged, oxidized top layers of the clear coat) whereas waxes and protectants (natural or synthetic, solid, paste or liquid, solvent or water based, polymers, silicones, etc.) fill up the low points and create a protective top layer.
Buying habits are influenced by the following components:
Product quality (durability, UV protection);
Reputable company name;
Loyalty (used brand in the past);
Word of mouth (from manufacturers, friends or family members);
Extent of surface damage,
Ease of use (convenience, operator experience and tool requirements);
Price vs. performance (customer expectation, economical or high-end service packages); and
Profitability (how much income the product can generate).
Recently increasing emphasis is being placed on product safety and environmental profiles, like biodegradability, toxicity, flammability, VOC (the content of volatile organic chemicals which can damage the protective ozone layer from the harmful UV radiations of the sun), sustainability, renewability (plant or petroleum based ingredients), etc.
Removing embedded or below surface contaminants
Most new cars are exposed to rail-dust while being transported from the assembly plants to the dealers. These are fine metal particles coming from the rails or from the upper electric power lines in form of sparks during transporting the cars via railroad from the manufacturers to the dealers. These embedded tiny metal particles can easily rust creating bigger pores/craters in the clear coat and make the whole coat more vulnerable to other attacks like acid rain, oxidation, UV radiation, etc.
Industrial fallouts and brake dust particles can also end up in the clear coat. You can easily determine if there are embedded surface contaminants. Gently run your fingertips over the washed and dried car surface (according to some recommendations you can place your hand into a plastic sandwich bag while testing the surface). You should feel a glassy smooth surface. If it is rough or coarse, there are contaminants which need to be removed.
The best way to get rid of these embedded particles is the use of a clay bar. Clay bars are soft, synthetic materials do not contain any abrasives, thus they do not cut, or polish the particles but safely pull them out. Many suppliers sell these bars with a lubricant, and recommend using them in small sections at a time. Clay bars are reusable as long as they are not saturated already with particles, or their surface is not dirty. Some of them are stretchable so that by pulling and refolding them a new clean side can be exposed for further use.
Claying can be done as frequently as necessary. If it creates a glassy and glossy smooth surface, no polishing is necessary. However, if the surface still contains oxidation marks, etches from chemicals like acid rain, deep stains from bird dropping or mechanical defects (scratches, swirl marks) further deep cleaning is necessary.
Deep cleaning is done by paint cleaners, polishes, compounds, finishing papers to remove those beneath the surface damages. A product with the right size of abrasive should be chosen based on the extent of the damage.
Whether the job can be done manually or by a machine depends on the extent of the damage and on your expectations. Follow the manufacturers’ recommendation. The most common machines are rotary buffers with a direct drive (the most powerful way to remove deep scratches, but needs extra caution and experience to avoid damage in the coat), dual action polishers and orbital buffers. The latter two utilize an oscillating circular motion which is safer to the top coat because they cannot exert too much force on one area at one time to damage the paint.
Build up protection, restore shine
When the surface is completely clean and free of any damage it still needs a protective aesthetic coating. The most important protectants are waxes (synthetic and natural), polymers and silicones (the latter one is a special class of polymers). These materials have different and overlapping characteristics as well.
Tremendous progress has been made in developing new multifunctional products which rely on these ingredients. The right question is not that which ingredient is the best: wax, polymer or silicone — but which formulated product has the right combination of these ingredients for a specific job. Combining these materials can be synergistic (the combined effect is greater than the sum of the individual one’s). Obviously, various car surfaces with different levels of damages, storage conditions, surface preparations, maintenance levels need different products.
In general waxes create a protective transparent film, which needs to be buffed to provide shine. Polymers and silicones are added to formulas to impart gloss, smoothness and protection to surfaces. New developments in this class include specially tailored molecules to fit the evolving needs of the car care industry. These new molecules can physically (via adsorption), electrostatically (opposite charges attract each other) or chemically (via curing) bond to the surface for extended protection, longer lasting shine, more durability towards repeated washing and pleasant surface feel.
However, none of these products will stay permanently on the surface, so they need to be reapplied depending on their predicted level of protection under use conditions, e.g.: outside or inside parking, driving conditions, climate (temperature fluctuation, precipitation), geographic location (industrial or rural area), quality of original finish, surface preparation, quality of product, etc. Application can be manual or with the help of a machine. Similar materials and machines can be used to those for polishing. Wax on cool surfaces out of direct sunlight. Elevated paint temperature makes buffing difficult.
Andras Nagy has spent the last 15 years in basic and applied research in car care and surface care related industries. He is employed by Evonik Goldschmidt Corporation, a global leader in specialty chemicals. He is a member of the American Chemical Society, holds a Master degree in chemical engineering and a PhD in polymer science. He can be reached at firstname.lastname@example.org or 804-452-5602.