Why and When we need to Polish Car

Here's how I classify polishes:

Compound - A compound, often called a rubbing compound, is a cutting polish designed to remove heavy oxidation, some common forms of paint damage and defects, and the scratches created by fine sandpaper.

Polish - A specially formulated blend of components designed to remove minor scratches, surface imperfections, water spots, acid rain spots, light oxidation, and the swirl marks created by compounding with a machine.

Glaze - A very fine polish.  Some glazes are safe to use on fresh paint, as they do not seal.  A glaze does not have enough cutting power to remove imperfections, but will increase surface gloss.

Pre-wax cleaner - A polish containing chemical cleaners to help remove minor surface contamination and dirt not handled by normal washing or claying. You may be asking why I didn't mention detailing clay.  While detailing clay is an abrasive suspended in a clay or elastic base, its purpose is to remove particles from the paint's surface and not the paint itself.

Car Polish Selection

The car care market is flooded with polishes, each promising to work one miracle or another.  Selection is difficult at best.  For the purpose of our discussion, it's necessary to create a reference. It's important to note that polishes may be specifically created for hand or machine use.  The difference between a machine polish and a hand polish is how the abrasive material breaks down in use. 

The abrasives in most polishes break down (diminish) into finer particles, allowing the polish to "buff out."  If you use a machine polish by hand, the particles may not break down, and the finish will not buff out properly. Conversely, using a hand polish with a machine will cause the polish to break down too quickly, and you won't get enough cutting action.  A few polishes work by hand or machine, because they don't use diminishing abrasives or they are not temperature sensitive (buffing pads create heat).

Reasons to Polish Your Car's Paint

Many people believe that cars come off the assembly line with perfect paint.  That's far from the case.  There are many conditions that cause minor paint flaws requiring additional finishing work.  Dust nibs (small particles that land in the paint while it is still wet) are a good example.  Most car manufacturers take care of these problems at the factory using abrasive finishing materials.  Sometimes it is the car dealer who recognizes the flaw and fixes it.

Repairing minor paint flaws through polishing is not harmful to the paint system unless you remove too much paint.  If more than 50% of the clear coat finish is removed, you stand a good chance of premature paint system failure.  If more than 75% of the clear coat finish is removed, you will experience immediate paint system failure.  It can be a very fine dance between success and failure. Here's a general rule to follow.  If a scratch or other flaw can be felt with your fingernail, it's too deep to be completely removed through polishing.  That's not to say that polishing won't help hide the flaw; it will.  

Take a look at the following 3M diagram showing paint layers and minor scratches (marring) in the clearcoat surface.  These scratches can be removed completely through polishing, because more than 50% of the clearcoat would remain.

• Scratches - Surface abrasions that do not extend past the first 25% of top coat material can be fully repaired by polishing.  Deeper scratches can be improved as long as they do not fully penetrate the color coat into the primer.
• Scuffs and rub marks - Scuffs are broad, shallow surface abrasions that are easily repaired by polishing.  Rub marks are commonly caused by shoe heels (getting in and out of the car) or the bumpers of other cars.  The rub mark is generally a transfer of rubber or other vinyl material to the paint surface.  Rub marks are easily removed by compounding and polishing.
• Micro marring - Micro marring, also known as swirl marks and spider webbing, means very small scratches in the paint's surface.  Micro marring is created by machine compounding and in everyday use and maintenance of the vehicle.  Micro marring is easily removed by compounding and polishing.
• Etching - Paint etching is a common problem caused by hard water (tap water) or acidic water (acid rain).  Bird droppings are another common cause of paint etching.  Depending on the severity of the etching, polishing will repair or lessen the appearance of etched spots.
• Dust nibs - Small particles of dust and other foreign material that land on the paint during the painting process create small nibs on the surface.  Wet sanding, compounding and polishing will remove the visible portion of the nib and level the paint.
• Orange peel - When a car is painted, the paint is applied at a consistency and thickness that allows the paint to flow (briefly) and level.  If the paint is applied too heavily, sags and runs will result.  If applied too thinly, the paint does not properly flow and level, causing an uneven surface called orange peel.  If the orange peel is not severe, abrasives can be used to level and glaze the finish to match the rest of the vehicle.
• Runs and sags - If paint is applied too heavily, sags and runs will result.  If the sag or run is in the clear coat, it can be repaired, but not if it is in the color coat or primer.  On a non-clearcoat paint, sags and runs in the color coat can be repaired.