Automotive Paint Thickness Gauge: Detailing User Guide (2024)

By Christopher Brown of OCDCarCare.com

As a professional auto detailer, have you ever wondered: “is it really necessary to use an automotive paint thickness gauge (paint meter) for detailing paint correction projects?”

“No,” is an acceptable answer IF…

– You’re an adrenaline / chaos junkie who lives to roll the dice, living on the edge whenever possible.

– Or your local business is okay with potentially damaging customer vehicles and losing money, reputation, and market trust.

However, answering: “yes, it’s necessary to use a detailing paint thickness gauge for paint correction projects,” highlights an entirely different set of reasons and motivations.

Is an Automotive Paint Thickness Gauge (PTG) essential for achieving quality paint correction results?

No, but it does have a huge list of positive benefits, that once realized and understood, are nearly impossible to ignore.

1. Explain Why Paint Thickness Gauge’s (PTG’s) are Essential Tools for Modern Auto Detailing Businesses
2. Define what a PTG does (and does not do) Effectively
3. Explain How Paint Thickness Gauges Measure Automotive Paint
4. Discuss How to Effectively Measure Vehicle Paint Using a PTG or Paint Meter
5. Present Ideal Auto Detailing Situations for PTG (Paint Meter) Use
6. Illustrate How PTG Use Decreases Liability for New Vehicle Auto Detailing Services
7. Explore what Automotive Paint Thickness Readings Mean for Detailing Paint Correction

As discussed in a previous article, explaining automotive paint systems and individual vehicle paint layers, modern automotive paint is thinner than ever.

Thinner vehicle paint means less clear coat (paint’s protective layer) exists from the automotive manufacturer. Therefore, thinner factory clear coat levels mean less detailing paint correction services may be performed over the lifespan of new vehicles.

As a quick reference, average total paint thickness on contemporary OEM (factory) vehicles ranges between 95-125 microns (~3.7-4.3 mils) thick.

The clear coat paint layer generally accounts for ~40% of the general thickness of automotive paint systems. Therefore, most modern vehicle paint clear coat thickness ranges from 38-50 microns (~1.49-1.97 mils).

This trend of thinner vehicle paint is a wakeup call for the auto detailing industry. However, it’s not new. Automotive paint levels have steadily declined in thickness from vehicle manufacturers over the last 20 years.

Detailing professionals, as an industry, must adjust their paint correction procedures to meet the constraints set by thinner modern factory paint systems. The sooner detailing businesses understand and adjust their approach and methodology toward less aggressive paint correction services, the better.

Otherwise, detailing business owners will eventually learn the hard knock lessons of overly aggressive paint correction on thin paint from:

• losing money: due to mistakes and lost job opportunities
• disgruntled customers: due to vehicle paint repairs caused by overly aggressive paint correction practices
• potentially harmful business reputation: spread by potential negative social media reviews
• disheartened employees, and/or frequent employee turnover: due to vehicle damage occurring from following shop procedures

The automotive paint thickness gauge (aka paint meter or paint depth gauge) is a critical and invaluable tool for detailing paint correction. However, like all technology, it has limitations. Despite the marketing of some popular detailing supply websites, PTG’s cannot live up to many of their overhyped marketing claims.

What follows are some guidelines defining the abilities and limitations of a paint thickness gauge for auto detailing.

Over time, paint thickness gauges (paint meters) have proven hugely unreliable to read paint’s total film build on non-metal (non-ferrous) substrates. Therefore, painted vehicle components made of plastic, carbon fiber, fiberglass, and other non-metal panel materials cannot yield accurate estimates of overall paint thickness from a PTG.

While some PTG manufacturers claim this ability, when put into real world practice, the devices return unreliable and/or wildly varying results at best. Displaying vastly different reading in the same area with successive measurements is the opposite of consistency. And no real professional wants to make decisions based on unreliable or incomplete information—it’s just bad business.

Secondly, an automotive paint thickness gauge (paint meter) cannot accurately read the individual layers of paint on a vehicle. This is true, no matter what manufacturers or sales-based websites may claim. This was confirmed many times with many phone conversations with several PTG manufacturers– especially d3#e1$&0.

On principal alone, its best practice to use a paint thickness gauge (PTG) to measure vehicle paint levels prior to every auto detailing paint correction service. This practice verifies if all automotive panels contain enough clear coat to safely work on for paint correction (aka buffing or polishing) services.

If for no other reason, this policy enables detailing businesses to know if have the potential to deliver on the customer’s desired outcome.

Finally, this practice protects both detailing businesses and vehicle owners from awkwardly difficult conversations and tons of stress, resulting from accidental vehicle damage from overly aggressive polishing on thin paint.

Some may think or argue it’s a silly practice to measure paint all vehicles, including brand new vehicles. However, limiting exposure to liability is generally both a smart customer service practice and sound business policy. Therefore, spending ~10 minutes to measure each vehicle’s available paint system seems pragmatic and worthwhile in every way.

Again, as a business owner, the practice of measuring paint before every paint correction service could save the business many headaches. Every time a vehicle is accidentally damaged in the shop, the business loses money from: a) the labor & consumables used on that job and b) on the damage repairs. In addition, the business accrues lost opportunity costs from profitable projects due to damaged vehicles.

These missed opportunity costs occur in two timeframes. First, the original opportunity for profitable work disappears when a vehicle is damaged. Secondly, other profitable projects cannot occur when the damaged vehicle returns from repairs and original services must be redone.

To conclude, purposefully allotting ~10 minutes to test each vehicle’s baseline clear coat levels, before starting paint correction services can potentially save businesses from losing revenue, high levels of stress, and negative marks on reputation. And potentially a bill for a new phone for quick-tempered and reactive individuals.

An automotive paint thickness gauge is an invaluable tool to investigate inconsistent paint finishes noticed by the eyes.

Nothing replaces sharp well-trained human eyes and experienced instincts for locating repainted areas, entire panels, or mid panel spot blends. However, a detailing paint thickness gauge allows eagle-eyed auto detailers to verify if paint repairs did or did not occur on a panel.

Usually, visual paint inconsistencies display themselves in the form of paint color or texture differences. Most frequently, and probably easiest to detect for experienced auto detailers, are changes of paint texture (aka orange peel) between panels.

As mentioned previously, automotive paint thickness gauges (paint meters) cannot accurately measure non-ferrous panels. However, metal body panels, immediately adjacent to non-ferrous panels, are measurable. Measuring these neighboring panels yields useful information for detailers to find repainting clues.

When repainting automotive panels, painters try to best match the newly painted areas with the vehicle’s original paint. Blending occurs through matching the new paint with the original, either on one large panel or adjacent panels touching the repaired area. For example, picture repainting a full door. Depending on age and condition, generally about 30cm (12in) of the adjacent panel, on either side, may be lightly painted to best ‘blend’ that door to the original paint.

Therefore, if a bumper is a repaint suspect, investigate the entire scene. Meter the adjacent panels bordering each side of the bumper. If the first 30cm (12in) of the adjacent panels display paint levels noticeably thicker paint levels than the rest of the vehicle—it’s likely that bumper was repainted.

If a vehicle is 5 years old +, or has unknown ownership and care history, it’s a good insurance policy to know how much paint is on the vehicle. Especially if the vehicle appears textured grey and the owner wants it restored to a mirror like jet black finish!

Its best practice to measure the paint level on vehicle panels, if any or all the following conditions apply:

• The vehicle is 5yrs old, or older
• The vehicle lived its entire life outside 24/7
• The vehicle has unknown owner and care history

Automotive Paint Thickness Gauges (Paint Meters) accurately measure paint on vehicle metal substrates using technology similar to a ship’s sonar.

Paint Thickness Gauges use sound waves to take measurements. PTG’s generate ultrasonic sounds wave that shoot down, through all automotive paint layers, to the metal and bounce off and back up to the meter for analysis.

The meter determines the total thickness of all automotive paint layers by calculating the length of time the ultrasonic wave travels down to the metal substrate and back to the internal sensor.

Contrary to popular belief, many brand-new vehicles contain spot repairs. Therefore, its critical for auto detailing businesses to incorporate paint thickness gauge measuring into all vehicle intake procedures, prior to starting any services.

Most potential auto detailing paint correction related issues, on individual panels or entire vehicles, are uncovered and potentially prevented by measuring the paint thickness of available vehicle panels. This is noteworthy since repairs, caused by shipping damage of new foreign vehicles, frequently occur inside US port-based manufacturer facilities.

These auto maker locations operate inside Free Trade Zones (FTZ’s). The FTZ’s, even if located on US soil, are legally zoned as territory outside the US.

Inside FTZ locations automotive manufacturers can assemble, manufacture, repair, store, test, destroy or endlessly modify goods—all while considered outside US territory.

Only when goods leave an FTZ are they considered to reside within US soil. In the moment items officially leave the FTZ (secondary factory) they legally become goods, immediately subject to import duties, excise taxes, etc.

This is relevant because newly minted foreign vehicles ship directly to FTZ’s within, or adjacent to, US ports of entry. Upon US arrival, these automobiles undergo inspection inside auto maker FTZ facilities.

If a vehicle suffers any damage during the transporting process, it is immediately fixed inside the FTZ facility. Any vehicle repairs and/or repainted panels, performed within FTZ facilities, are considered OEM (factory).

Since repairs inside FTZ’s are considered ‘factory official’ the repairs are rarely disclosed–if ever. This explains how and why imported vehicles frequently display tiny spot fixes, entire repainted panels, or even entire vehicle sections–even though the vehicle is considered ‘brand new.’

The only way to know if new vehicles have spot repairs is to measure with an automotive paint thickness gauge.

For auto detailing businesses an automotive paint thickness gauge (PTG), or paint meter, is a powerful tool to both properly evaluate vehicles to generate profit and to avoid liability. However, the tool is basically worthless if it’s not accurate, and its usage does not produce consistent and reliable results.

Accurate measurement of vehicle paint, using an automotive paint thickness gauge, requires proper steps and consistent usage habits.

The following 4 steps outline effective procedures for measuring automotive paint and vehicle evaluation, using a paint thickness gauge (PTG).

All paint thickness gauges (paint meters or paint depth gauges) require verification of calibration, straight out the box, to ensure accuracy.

Any quality detailing paint thick gauge (PTG) contains a ‘calibration kit’, included with factory packaging. Typically, these ‘calibration kits’ include various pieces of metal to simulate different panel substrates and assorted thin clear plastic sheets. The thin transparent plastic sheets, labeled with their thickness levels, allow for gauge calibration testing.

To test paint meter’s calibration, place the meter into calibration mode. According to manufacturer directions, specific transparent plastic sheets (of fixed thicknesses) sit on top of included metal pads for testing. The PTG measures all thin plastic sheets, containing various thickness levels, to validate the meter’s accuracy.

Calibration testing confirms the meters accuracy to read automotive paint thickness within an approximate +/- 1-3% standard deviation. Therefore, if the test film plastic sheet displays 30 microns and the meter reads anywhere between 29.7-29.1 microns, the meter falls within proper calibration. In other words, its accurate and ready to professionally test vehicle paint levels!

If the paint meter falls outside the standard 1-3% deviation, then follow the PTG manufacturer’s manual for a reset procedure. If the meter has no ability for adjustment, then immediately return the meter for an accurate replacement.

Note: Calibration testing and settings for all PTG’s differ, so it’s always best to consult the manufacturers included instruction manual.

To ensure a vehicle is a candidate for detailing paint correction, its necessary to know the baseline of paint thickness- throughout the entire vehicle.

Baseline automotive paint system thickness is the average amount of paint which exists on all panels.

Finding the baseline paint levels reveals info, or clues, about the average paint thickness of the original paint, resprayed panels, and/or current state of the paint system.

Obtaining this data allows business owners to then choose the best course of action for paint correction services.

For older vehicles, a baseline of OEM (factory) paint thickness helps determine the safest paint correction steps for the desired services of the vehicle owner—according to the available amount of paint on the vehicle.

If a vehicle is exceedingly old, and/or has unknown history, it’s sometimes near impossible to find baseline paint thickness. The best sources of information stem from examining any protected painted areas as reference points. These points frequently act like time capsules, showing both the old aesthetic of the paint system and often close to its original thickness.

Commonly jambs areas, particularly door jambs, will yield information surrounding the original thickness of the factory paint system.

Additionally, the large vertical flat edges of doors (near the latch assemblies) usually remain untouched over a vehicle’s lifespan.

The driver and passenger side door jambs will likely provide the greatest and most accurate info for factory paint thickness. However, know the paint thickness levels of jambs is not gospel, but a potential guide for how much paint the vehicle started with.

Some auto makers carry reputations for cutting corners, spraying very little paint in these areas to limit cost and production times.

When evaluating a vehicle’s overall paint thickness, it’s also a great practice to thoroughly check common impact areas to verify if a vehicle contains body repairs.

Common vehicle impact areas where paint or body work repairs frequently occur include:

• Front bumper
• Hood
• Front Fenders (driver & passenger side)
• Along the Edges of Driver, Passenger, and Other Doors
• Adjacent leading edges of panels directly in front of or behind driver or passenger doors
• Rear quarter panels

Paying close attention to these areas yields definitive evidence if a vehicle has or has not been in a collision. Accurate measurement information is invaluable for deeply evaluating used vehicles or to help determine the appropriate level of paint correction for all vehicle panels.

The value of rare and/or ‘classic’ vehicles is exceedingly higher if they are original, meaning they contain zero paint or body work. Measuring the film build on an entire vehicle with a paint thickness gauge will reveal if full vehicles, individual panels, or tiny spot areas contain repairs.

While this data will not reveal insights about what work was done, when, or why–it will demonstrate if the seller or broker leans toward honest or greasy sales tactics. And, with the data available from measuring, asking simple questions can either validate or poke holes in the seller’s stated vehicle history.

To obtain accurate and trustworthy information a paint thickness gauge requires a consistent methodical approach. Therefore, a reliable procedure for physically measuring paint automotive thickness is equally as important as an accurate meter.

Auto detailing business must establish a solid and repeatable procedure for measuring paint thickness on vehicles.

This procedure must include the following elements:

• An order of operations. Establish where to start and the order to follow around the vehicle until measurement completion
• An established set of measurement points for each panel, depending on type. Best practice: divide a panel into even quadrants, measuring each quadrant independently.
• Establishing which panels are critically important to measure and verify, according to the job type.
• A method for tracking and displaying averaging measurements on panels or areas *
• A review methodology for overall vehicle evaluation *
• A storage method for each vehicle’s paint thickness data for liability insurance *

Since 2016 automotive paint thickness levels of global vehicle manufacturers have averaged between 110-125 microns (~4.3-4.9 mils).

However, in the United States, Ford and General Motors consistently produce vehicles with OEM (factory) paint systems as low as 95-105 microns (~3.7-4.15 mils).

Therefore, it’s critical to understand what paint thickness gauge (PTG) readings mean, or implicate, for auto detailing paint correction services.

Automotive paint thickness gauge readings, averaging between 110-125 microns (~4.3-4.9 mils) fall within the general range of most modern factory vehicles. Additionally, some paint systems, such as pearlescent finishes, may display average thickness levels about 10-15% higher.

Vehicle paint thickness levels, reading between 110-125 microns (~4.3-4.9 mils) indicate enough paint exists for detailing professionals to go about their business and correct paint ‘normally.’

Speaking of normal paint correction; let’s define it.

Normal paint correction refers to automotive paint polishing services grounded in paint preservation, featuring the least combined aggressiveness to reach the customer’s desired outcome. For this reason a more fitting term might be responsible paint correction. Because the entire goal of detailing paint correction should be to make vehicle owner’s happy, while leaving maximum clear coat (paint’s protective layer) on the vehicle.

Normal does NOT include sanding entire vehicles to remove texture aka orange peel for aesthetic gain. Because that is a completely unnecessary and harmful practice for the longevity of OEM (factory) paint. Sanding vehicles for aesthetic gains, to remove texture (orange peel), is completely opposite to the concept of preserving factory paint.

The term ‘bad’ might sound overly harsh. However, it’s important to mark this range of vehicle paint thickness as yellow alert territory in any detailer’s mind.

Automotive paint thickness levels, measuring between 90-100 microns (~3.5-3.9 mils), is where detailers must start weighing their options. In this range, vehicle paint thickness levels enter the thin side of the spectrum and require different considerations.

This range of paint thickness forces detailing businesses to choose a path of action. Detailing businesses make paint correction choices based on either long-term benefits for vehicles and owners or for their own short-term pocketbook.

If paint reads toward the bottom of this range (90 microns) then performing a deep two step paint correction may prove more detrimental over time. While it may remove most all of the defects and beautify the surface, it may remove too much clear coat when the total starting film build is already on the lower end of the spectrum. Therefore, an invasive deep cutting two-step paint correction may remove a large portion of the remaining clear coat. Over time this could potentially jeopardize the long-term integrity of the vehicle’s paint.

Alternately, performing a light one step paint correction at this paint thickness range would still improve the appearance of the vehicle. The benefit of a single stage paint correction is leaving more original clear coat protection behind to ensure longer life for the automotive paint system.

Any vehicle paint thickness reading at 75 microns or ~3 mils, or lower, is a major red flag.

Best practice for automotive paint thickness at or below 75 microns is to avoid paint major correction services. And it may be wise to avoid any and all paint correction entirely. With paint this thin, one mishap may cause a burned panel or section which is only fixed by repainting.

However, if some sort of paint correction or polishing is required, then the best approach is to purposefully obsess about preservation.

Keep the paint correction super light, leaving as much clear coat on the vehicle as possible. This means focusing on creating clean and shiny paint surfaces, instead of prioritizing defect removal. This is the textbook definition of a gloss enhancement paint correction service.

To achieve ‘pretty looking paint,’ without much defect removal, use a finishing polish paired with a medium foam pad.

Additionally, automotive paint levels, at or below 75 microns, are ideal scenarios for paint correction liquids containing durable fillers. Fillers, inside detailing paint correction liquids, work ‘improve’ automotive finishes by covering up defects. Durable filling agents target light defects like fine to medium scratches by ‘filling’ them in, so they are no longer visible.

Finally, the best practice is to use a ceramic coating primer polish that provides light correction, potentially fills, adds coating film build thickness, and prepares the surface for optimal coating bonding.

In this scenario, its best to pair the primer polish with a mild ceramic coating featuring moderate carrier solvents. A coating with aggressive carrier solvents may negatively interact with the already diminished paint system.

For automotive paint levels at or below 75 microns, the primer polish and mild ceramic coating approach ticks all paint preservation boxes. It leaves the best aesthetic result, minimizes the amount of clear coat removed, and adds measurable and durable protection behind with the ceramic coating.

A variety of weird or strange paint measuring scenarios exist which do not exactly fall into the previous categories listed above. These situations clearly raise a red flag showing some sort of body work or painting have occurred on the vehicle—no matter their unknown origin.

What follows are commonly strange situations that occur during when measuring automotive paint with a paint thickness gauge:

• Paint thickness readings, in small areas of a single panel, registering 10, 20, 30, 50, 100 + microns higher than the rest of the vehicle’s average paint level–are a red flag.
• Any paint thickness readings, on whole individual panels, registering 10, 20, 30, 50, 100 + microns higher than the rest of the vehicle’s average paint level–are a red flag.
• Any “N/A” meter reading, or inability of a meter to take a reading is, usually a clear indication of body filler work. Typically, Bondo or some other brand of automotive body filler, is used to fill-in or even out areas of the body.

Automotive body work is performed before any primer is sprayed onto a panel. Proper body work is quality checked to ensure it seamlessly blends with the existing panel or overall vehicle finish. A major point of focus of quality body work is matching the surface height and texture of the existing finish.

Poor quality body work instantly draws attention from the eyes. Often, it occurs because someone gooped body filler (Bondo) onto an area and didn’t bother looking at the repair from more than one angle. Other times, poor body work is not sanded down to properly match the rest of the panel. And it may even contain a strange texture or evidence of application marks.

Measuring a vehicle’s paint thickness, on every available panel, is the best practice for detailing paint correction services. This allows auto detailing businesses the ability to accurately understand each vehicle’s starting condition before services.

Accurate clear coat measurements, from consistent and thorough PTG measuring procedures, reveal the overall amount of material is present on vehicle surfaces.

Once vehicle paint thickness levels are known, detailing businesses must then weigh this information against the type, amount, and severity of defects. This method enables detailers to find appropriate paint correction service levels, allowing for safe and maximum defect removal for each panel.

The best auto detailing businesses incorporate an overall context for paint correction services aligning with each owner’s vehicle goals. A complete context includes the owner’s aesthetic, functional, and long-term vehicle objectives.

To close, let’s the review concept of paint preservation. This was originally covered in greater depth as the final topic of the OCDCarCare Los Angeles article explaining the 5 thin automotive paint layers relating to detailing paint correction.

Detailing businesses are expected to improve owner vehicles, not damage them. If unnecessarily aggressive paint correction removes excess clear coat, paint’s protective layer, then damage occurs. While not visible, this damage may potentially jeopardize the long-term integrity of the vehicle’s paint system.

Therefore, all auto detailers and detailing businesses, should approach all paint correction projects with the philosophy of paint preservation. Under this mantra, the lowest amount of clear coat is removed, according to the service dictated by client preferences.

The paint correction preservation mindset and method is best for both the vehicle and the owner.

And the only way to know if it’s safe to meet the client’s desired result, for their unique vehicle, is to measure the paint accurately and thoroughly with an automotive paint thickness gauge (PTG).

Therefore, for successful and profitable auto detailing businesses, its absolutely vital to use an automotive paint thickness gauge (paint meter) to test all vehicle panels before all paint correction services. This truth is strengthened as modern factory paint systems continuously evolve and become thinner over time.

“ALWAYS Keep Learning to Strengthen Your Passion & Your Business.”

© Christopher Brown – OCDCarCare Los Angeles