How deep is too deep? Paint Defect Removal.

[Todd@RUPES]

How deep is too deep?


How much is too much would be another relative title for this article.

When it comes to paint correction and removing swirl marks it is easy to get carried away and try to remove every possible paint defect in a never-ending quest for perfection. However, in many cases not only are we creating more work for ourselves but we risking long-term and short term damage.


What are paint defects?

Before divulging deeper into the conversation a review on paint defects can be found in this thread: Detail Institute- What are paint defects? Generally the term paint defects refer to any surface that it is not level to the rest of the adjacent paint. Above the surface defects would include blistering in the paint, dust nibs that landed during the paint, scratches (both microscopic or visible) of varying depths, runs, or extreme paint textures such as heavy orange peel. For this topic and article we are referring solely to below the surface defects such as swirl marks (microscopic scratches) and gouges that penetrate the paint`s surface.


How are paint defects removed?

Various techniques and procedures are used to remove paint defects, but all use some form of abrasion to level the paint until it is near flat (to the adjacent areas). To remove a scratch from the paint means bringing leveling the surrounding paint until it is level with the lowest point of the scratch. This means that every time that defects are removed some paint (or clear coat) will be removed as well. How much material (paint or clear coat) that must be removed is dependent on how deep the paint defects that are being removed penetrate into the clear coat.


How much modern paint can be removed during the polishing process and how much is too much?

The overwhelming amount of modern paint systems use a base coat/clear coat paint system. The base coat contains the color is thin and flat (semi reflective) in nature. The clear coat is sprayed on top of the base coat and is highly reflective. It is also responsible for the UV protection of the base coat (preventing color fade). On modern paint systems, the clear coat is what becomes scratched, scoured, or damaged and is what is being polished.

Most OEM car manufacturers and paint suppliers recommend that no more than 10-20% of the clear coat is removed during the polishing process or UV protection will be greatly diminished. This could lead to long term damage such as paint fading or all out paint failure. On areas of high UV exposure (such as the top 1/3 of the vehicle) it is critically important to maintain maximum paint/clear coat thickness.

Modern clear coats range (depending on manufacturer) from approximately 2 mils (.002 of an inch) to 4 mils (.004 of an inch) in thickness. A dollar bill is roughly 3.5 mils in thickness for a general comparison. Sticking the OEM recommended amount of material removal, only .2 mils (.0002 of an inch) to .8 mils (.0008) of an inch of clear coat should be removed to maintain maximum UV protection.

How deep are typical paint defects?

There is not such thing as a common paint defect, particularly as it relates to swirl marks and deeper marring. The depth of the marring is determined by how much pressure was applied to the object causing the marring, the type of object, and how resistant the paint is to marring (it`s hardness). In general most swirl mark marring is microscopic in natural and is only visible because light refracts off the edge of the mark. It is not uncommon for these marks to only penetrate .05 mils (.00005) of an inch or less, meaning they can be removed multiple times with out comprising the paint`s thickness. However some random isolated deeper scratches (RIDS) can easily penetrate from .1 mil to .5 inch thick. Any defect that you can feel by dragging your finger nail over the paint is likely 1 mil or more deep and should not be repaired from factory paint systems.


Is a paint gauge necessary for paint correction?

Yes and no. If you are a professional detailer or an enthusiast who is concerned with having your car (or your client`s cars) as near perfect as possible, then using a paint gauge is extremely recommended. Paint gauges come in two forums: magnetic, which can measure metals (most quality gauges such as the Defelsko Posi Test DTF can measure both ferrous and non-ferrous metal) and ultrasonic which can measure the paint thickness on composites such as plastic, fiberglass, and carbon fiber.

When measuring paint on metal body panels you can only measure the total thickness (the space between the top of the paint and the metal) of the entire paint system. There is no way to know what percentage of that material is primer, what is base coat, and what is clear coat. Most modern cars, due to increases in body panel manufacturing, use extremely thin layers of primer. Most older cars used very thick primers in order to hide any imperfections in the body panel. However there is no tried-and-true method of knowing exactly what you are working with.

Using a paint gauge is extremely powerful tool for reference, whether measuring the total amount of material removed over the life of a vehicle, or how much is being removed during an intense re-leveling of the surface. This is even more valuable if you are truly concerned about getting your paint as defect free as possible and keeping it that way for the life of your vehicle. If you are an enthusiast who prefers his paint to look good by giving it a mild polish every couple of years that a gauge may be overkill.


Err to the side of caution.

If your vehicle is driven frequently and subjected to the environment regularly than maintaining maximum paint thickness is the priority. Using a two step paint polishing system (starting with a swirl mark removing polish and finishing with a gloss enhancing final polish) will usually provide great results with out removing too much material. There will likely be RIDS remaining but these do not usually reduce gloss and shine. Keep in mind that it is better to have really good paint that has enough material for future polishing then to have perfect paint that can never be polished again.


Keep it looking great.

Using proper washing techniques, such as those described in these threads: How To: Wash Your Car Using The Two Bucket Method or How To: Rinseless Wash Your Vehicle will go a long way towards eliminating future paint defects and severely limiting the depth of new ones. As long as the paint defects are extremely shallow then the future polishing can be kept extremely fine and maintain maximum paint thickness, while keeping your car looking great.

[Concours.John]

I`ve said it before and it again. It`s good to have someone who can explain things in a descriptive manner that is easily understood.

I refer people to read your articles here when explaining the process.

Nice article!

[Todd@RUPES]

I`ve said it before and it again. It`s good to have someone who can explain things in a descriptive manner that is easily understood.

I refer people to read your articles here when explaining the process.

Nice article!

Thanks John!

[wendell jarvis]

Speaking in general to deep scratches, my rule of thumb is if you can feel it with your finger nail its probably too deep

[Todd@RUPES]

Speaking in general to deep scratches, my rule of thumb is if you can feel it with your finger nail its probably too deep

A great rule of thumb for one time paint defect removal.

[Addicted2Bling]

Great article, I had no idea clear coat was that thin, that makes me want to go out and buy all the opti-coat I can get!

[glfahlc]

i have deep scratches on the side of my truck i`m afraid i won`t be able to remove completely. its through the paint and into the primer unfortunately but i will see how much i can smooth it out next spring. pictures forthcoming. thanks for the explanation todd and i enjoy reading your writeups...

[ca.detailchick]

This is really good information.

Many people dont understand there is not an infinite amount of paint you can take off .

Especially some of the newer vehicles have very little clearcoat.


I once had a customer who argued with me that a scratch would come out ,but it was all the way down to the primer . He still didnt get it after I explained it to him and insisted it would come out

[mikenap]

I once had a customer who argued with me that a scratch would come out ,but it was all the way down to the primer . He still didnt get it after I explained it to him and insisted it would come out

Man, some people only believe what they want to believe.

[Pats300zx]

Great writeup Todd. Top Notch

[Todd@RUPES]

The fingernail is trick is great for new cars or cars that you are very familiar with their polishing history. It was taught to me years ago by Mike Phillips (in Tampa at a roadshow in 2006ish) and it is something that I have taught to others. The only draw back is if you are unfamiliar with the paint.

Imagine the car has been buffed many times before (perhaps a scratch had already been removed from that area) and you attempt to remove another one. This is why I would strongly encourage somebody who is detailing professionally or working on various cars to consider a PTG (Paint Thickness Gauge). This provides a powerful frame of reference to surrounding panels and could prevent a costly mistake in the future.

[RaskyR1]

Great article Todd!



To answer the question in the thread title.....this would be considered too deep!

[Todd@RUPES]

Here is a link depicting the common thickness of household items in relation to how thick paint is. LINK