Many of you will have seen some of the detailing work I post up on here.
I thought I'd put together a short guide of the most common paint defects seen on cars, as well as a bit of info about what paint correction is and what it entails.
Paint Defects
Swirls
This is by far the most common paint defect on cars. Paint swirls are minor scratches in the clear coat and generally caused by improper washing/drying techniques, or by dry rubbing of the paint with no lubricant (eg a quick detailer product). They're generally circular as most people wash/dry/buff their cars in a circular fashion. You see them the most easily in direct sunlight or under high levels of fluorescent lighting or metal halide lighting (eg. service stations or some car park lights)
They are difficult to completely avoid in daily drive cars, however with correct maintenance they can be minimised.
Here is a 50/50 shot of the same area. One half has been polished, or "paint corrected" by machine and buffing pad
Etching
The most common type of etching is water spotting
This is where water has dried on the panel and the minerals/metals in the water that are left behind etch themselves into the clear coat. There are a number of different types of water spots, which I won't cover in too much detail, suffice to say some can be removed with a paint cleaner product like Prima Amigo, and others, due to their severity need to be machine polished out (paint corrected)
The way to avoid water spotting is to ensure the car is dried properly after washing, and always to have a layer of protection over the paint to bear the brunt of this sort of potential damage. (eg a sealant, wax, or both)
The other common type of etching is from bird poo
Bird and bat poo can be quite caustic and damaging to paintwork if left on for a sustained period of time. If not removed within a day or so of occurring it will almost certainly cause damage to bare unprotected paintwork. Sometimes damage can occur within a few hours if it's a hot day and the car is in direct sunlight.
Always try to clean off bird/bat poo as soon as you can. Use a damp microfibre towel or even a wet paper towel in a pinch. Lightly wipe away the bird poo. If it's dried on the panel, don't scrub! that's the quickest way to put swirls in your paint. Use a quick detailer product such as Prima Slick or Hydro to saturate the area, let it dwell for a min or so, and then very lightly wipe it away
Buffer Trails (AKA Holograms)
These are not a natural occurrence. These are 100% caused by humans using machine polishers.
Buffer trails are a by-product of heavy machine polishing. Sometimes while paint correcting, a detailer will need to work some areas quite heavily (compound) to remove deeper swirls and scratches. This will quite often generate heat in the panel due to the friction of the polisher working out those swirls. This will manifest as buffer trails (holograms) in the paint surface, thereby necessitating a follow-up polish with a lighter pad/polish combination to remove the buffer trails and enhance the clarity of the paint.
For a detailer, sometimes it's a necessity to create buffer trails in order to remove or reduce the heavier scratching in a car's paintwork. The mark of a good detailer though is how well they remove those buffer trails and "jewel" the paint surface (jeweling is the art of lightly machine polishing/finishing a paint surface to achieve maximum gloss).
Orange Peel
Orange peel is not technically a paint defect, more a product of the paint application process.
The term orange peel derives its name from the way a painted surface appears rippled, like the peel of an orange. It happens as part of the spray painting process and generally caused by the airstream of the spraygun as it pushes out the paint onto the panel, causing a ripple effect in the paint.
The only way to get rid of orange peel is to sand it out and 'level' the paint surface of ripples. As you could well imagine, sanding a car is a risky prospect and should never be attempted by anyone who does not 100% know exactly what they are doing and have the correct tools to do the job.
On modern cars, paint is generally applied much thinner than cars 10+ years ago. Generally due to robotic automation being able to cover areas more evenly with less paint than human painting. So this can make strike through while sanding a car even more possible.
Here is a before photo showing average orange peel on a VW Golf
After levelling the clear coat by wet sanding, and then finely polishing (jeweling) the paintwork the end result is:
Notice how there is much more definition in the reflection now that the light is reflecting more evenly off the painted surface. The light is not scattering nearly as much because the surface is flatter, making the surface more mirror-like. Some prestige car manufacturers, such as Aston Martin and Rolls Royce perform wetsanding to level out orange peel as part of the factory painting process. Most manufacturers don't due to the high amount of labour required and cost therein.
Images taken from Detail World in the UK. If you want to see some top notch wet sanding work, have a look at this link: Kelly@KDS Keltec and Midlands Car Care Wet Sand Tuition Detail - Edition 30 Golf GTI - Detailing World
On Japanese cars, it's generally quite difficult to achieve complete orange peel removal as the paint from the factory is very thin to start with. However with some Euro cars, especially prestige brands, it is something that can be done without sacrificing too much of the car's clear coat.
Which leads me to the next defect.......
Strike Through
Strike through is what happens in detailing when someone using a machine polisher or sanding goes past the depth of the clear coat and "strikes through" to the base coat beneath it. It most commonly occurs with inexperienced users not taking enough care while machine polishing. It can however, in rare circumstances, happen to seasoned professionals out of sheer bad luck (eg. an anomalous section of a panel that's significantly thinner than the surrounding area and not picked up in a paint depth check).
Sometimes strike through normally represents as a dull patch (indicating the polisher has struck through the clear coat into the base coat (the clear coat is what give a car its gloss. Without it the paint is quite dull)
In extreme circumstances it can even go past the base coat to the primer beneath
Once strike through occurs, the only way to repair it is to respray. This is why you should never attempt machine polishing or sanding unless you're 100% certain of what you're doing. Otherwise leave it to people who have the experience and know what to look for. A rotary polisher with a wool pad can strike through a car's clear coat in a matter of seconds if not controlled correctly.
Paint Correction
Paint correction, as the name implies, is the process of removing or minimising (correcting) paint defects.
There are several methods commonly employed when talking about paint correction
NOTE: Paint Correction, even by hand will remove glazes, sealants and waxes from the area you correct. If you have any of these on your car it is important to restore them once you've finished correcting the paint.
With regard to permanent coatings (eg Opticoat), any sort of paint correction can result in the coating being removed. DO NOT attempt any sort of paint correction if you have one of these permanent style coatings.
Hand Paint Correction
This method is the most accessible type of paint correction for people just starting out or those who want don't want to go to the (sometimes rather large) expense of buying tools and equipment for machine polishing.
Quite simply it involves a light liquid compound and a hand polishing pad of some description.
My personal favourites for these are
Mequiar's Ultimate Compound: Meguiar's Ultimate Compound 450ml G17216
and for the hand polishing pad, the Lake Country Orange Hand Pad: Lake Country CCS Foam Hand Pad Orange
These, combined with some good quality microfibre towels will help remove/minimise a number of spot defects in your car's paint, such as light (very light) scratches and scuffs, ring marks under door handles.
It won't remove heavy swirl marks or scratches, however it's not a bad solution for light defects requiring spot fixing.
Machine Polishing
This method of paint correction involves use of a machine to abrasively polish paintwork and 'level out' defects. This is the most common method employed by professional detailers and the most effective at removing defects across the entire car.
Within this machine polishing category, there are a few subsets of machines
Random Orbital (RO) Polishers
Most RO Polishers are effectively sanders. The only difference is instead of sandpaper, machine polishing pads are used. RO polishers oscillate back and forth in a random fashion to provide an even polish
RO Polishers are the safest of all machine polishers and the least likely to give buffer trails or strike through. It is obviously still possible if you try hard enough, however you'd have to be trying pretty hard.
They are a significant step-up from hand polishing and will give the user the ability to remove very light swirling, light etching and some buffer trails, dependant on the car and hardness of paint. They are limited though when it comes to heave correction as the can bog down very easily as pressure is applied on the paint surface. This is owing to the fact that these are not forced rotation or gear driven devices. They rely purely on high speed vibration for their polishing ability.
They are primarily a home user solution for machine polishing, however due to it's light action and coverage ability, some pro detailers still use RO polishers for application of glazes (with a no-cut machine pad), as large areas can be covered faster and more evenly than by hand.
Dual Action (DA) Polishers
DA Polishers are the next step up from RO. They oscillate in the same way as RO polishers, however they normally also incorporate a forced (gear driven) rotation element as well. Hence the term dual action. One action is the randome oscillation, the other is the forced rotating of the pad, thereby giving a greater cut ability while correcting paint.
There are a great many different DA polishers on the market of varying price, quality, and power. The lower priced-end of the market is aimed at the enthusiast and generally not designed for professionals who use and rely on their polishers day in and day out. They're typically (but not always) also lower powered units, which means the unit can still bog down on the paint surface if too much pressure is applied, though they generally take a fair bit of pressure before this happens.
High-end professional DA polishers will remove 90+% of surface defects that are able to be removed. They are generally very high powered, very solid, and comparitively very expensive tools. They are designed to be used 12+ hrs per day every day. Units like these are generally not recommeded unless you are detailing several cars a month or more and a) can justify the expense and b) have the skills and ability to use a polisher this powerful
Dual Action Polishers, have the potential to easily cause buffer trails and strike through and should be used with great care at all times.
Rotary Polishers
Rotary polishers have been around much longer than RO or DA polishers (decades) and have been the staple in detailing and also panel beating shops for many many years. For a long time they were the only method of paint correction.
These are the big guns of the machine polishing world. They are the most powerful and least subtle of all machine polishers.
Rotary polishers are a single rotational action, gear driven unit, generally powered by a high-spec motor that won't bog down under pressure
Rotary polishers are still in heavy use today by panel shops and professional detailers. They are most commonly used to remove deep defects in paintwork (very heavy swirls, sanding marks, some orange peel, etc)
Rotary polishers are the most dangerous of all machine polishers to use and should never be employed unless the user knows exactly what they are doing. The most common instances of strike through will occur with a rotary polisher and within seconds. I cannot stress how dangerous these polishers are. They should be treated with respect at all times.