Speed, kinetic energy (friction), applied pressure, foam pad actual surface contact area, pad and polish / compound abrasive ability, amount of surface lubrication available, area being polished, and material (paint, especially paint edges, plastic, metal, etc) heat conductivity. The above factors using a slow to stationary linier motion will produce excessive ‘friction heat ‘on a paint surface wither it be a rotary or an orbital polisher; the operative word here is excess friction



Basically strikethrough is caused when kinetic energy (friction heat) has compromised the clear coat and exposed the base coat. Paint often looks a slightly lighter colour; it’s usually concentrated on a small area or ‘spot ‘



You will also be able to see a non-glossy patch (base coat) where the clear has been removed with the edges of the remaining clear coat being visible. Some simple tests -if you drop water on to the haze, does the haze become clear or is there still some visible damage on the surface of the paint?



Take a light colored towel with some mild polish on it and gently rub the area. If you get colour transfer you`ve cut thru the clear and into the base coat.



You will need to apply base and clear paint or the strikethrough will remain visible. Since the clear coat contains the UV inhibitors, the colour coat is now exposed and will be subjected to photo degradation (fading)



• Speed - using too high a speed will not necessarily get the job done faster as there is a risk of instilling swirl marks or strikethrough, which will need to be corrected to remove



• Pressure - excessive pressure will make the pad / polish combination more aggressive, this has the effect of increasing kinetic energy (friction heat) which may result in a strikethrough, a friction paint burn or paint delamination from the substrate. Increased surface friction will also cause swirl marks



• Heat - excessive heat and a combination of excessive pressure (surface resistance) speed and an aggressive pad / polish combination will rapidly generate surface heat, this will soften the paint and may cause delamination from the substrate, surface hazing, strikethrough and greatly increase the chance of swirls.



• Pad angle – relative to the paint surface ideally the pad should be operated flat to the surface; this provides the correct contact surface area along with sufficient surface lubrication from the polish oils. By turning a pad on an angle you reduce the surface area contact, increasing pressure and kinetic energy (heat) while, reducing the amount of surface lubrication available.



• Insufficient product - without the polish lubrication oils, dry buffing will cause delamination from the substrate, surface hazing, strikethrough and greatly increase the chance of swirls.



Applying pressure and holding the polisher stationary in one area for too long will cause friction heat to be concentrated on a small area, especially with a foam pad due to their high surface resistance (friction heat) although a wool pad has a much lower surface resistance they are more abrasive.



Be cognizant that plastic parts and fibreglass panels have a lower heat transfer coefficient than metal and will therefore ‘spot’ heat



Paint Burn



Paint burn and Strikethrough have very similar cause and effect and these terms are often used interchangeably. Urethane clear coat uses a catalyst (hardener) if you heat it to beyond its melting point it will fracture and result in ‘paint burn’.



Although it is usually a combination of things, the most common cause of paint burn is thin paint (on an edge or end panel) a lack of surface lubrication (dry pad) and kinetic energy (friction) causing the pad to becomes more like a sanding disc, which produces excess surface heat, consequently the paint reaches its melting point and fractures



Clear coat provides both ultra violet (UV) radiation and the paint systems protection. Repair any breaches in the clear coat system otherwise you risk the paint drying out and delaminating, which will then require repainting



Areas of risk



Bumpers - often made of a composite material, they don’t conduct heat like metal panels, the paint in these areas, especially edges are generally thin (masking tape is good insurance)



Panel edges and seams - when approaching an edge always make sure the pad backing plate is spinning from the panel toward the edge and not coming from the outside to the edge where it can catch the edge and strikethrough.



Dry buffing



Dry buffing (polishing) refers to when the polishes lubricants run out; non-diminishing abrasives will start to emit a fine white dust, diminishing abrasives start to become translucent (similar to Vaseline® on a paint surface).



Once you polish much beyond these points is when friction from dry-buffing will cause ‘strike through’ (burn) of a painted surface and will normally entail a re-paint, it can be a very expensive mistake.



Also, keep the buffer moving across the finish to avoid excessive heat build-up and don`t apply too much pressure. Simply allow the machine and the abrasive do the work.