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Let’s talk about scratches with 3M
October 3, 2025 Verity Moring

Let’s talk about scratches with 3M

When time is of the essence, getting the job done right without the need for rework is vital. Sanding imperfections, such as scratches and pigtails, lead to visible repairs that need to be corrected. These defects may appear during the sanding process or after the repair is complete so preventing them to avoid any rework is key.

Taking time upfront can help save time in the end. 

1. Deep inline scratches while sanding filler.

Blocking with a coarse grade abrasive can leave deep scratches on a surface that resemble semi-straight lines put in from each pass.

Identifying these scratches on a panel can not only help visually show what the scratch profile looks like, but it can also tell us that we still have some work to do. 

2. Inconsistent scratch profile during blend panel prep.

While it may be difficult to see these inconsistent scratches with the naked eye, following sanding best practices and using the correct tools can help bring these issues to light before it’s too late.

Any visible bumps or shiny edges left, will need to be removed for an even, flat finish.

3. Unwanted pigtails during surface prep.

Pigtails are fortunately fairly easy to identify.

Unwanted swirl-like marks or scratches that resemble “pigtails” may appear on surfaces and should prompt technicians to course correct before spraying.

 

There are no shortcuts in refinishing. Every scratch matters and quality paint jobs start with quality body and prep work. Learn how these imperfections are caused and how they can be avoided below.

⚙️ 80 and 180 grit scratches should be non-existent.

At the start of the sanding process, the use of coarse grade abrasives are required (typically 80g, working upwards through the grades) to sand down and feather out filler and glaze. As a result, deep inline scratches are left on the panel.

✔️ Apply guide coat before each sanding step or grit change to easily identify and remove scratches along the way.

⚠️ Before applying primer, some tech sheets require prepping with no coarser than 320, sometimes even 400. You should not move on to the primer step without removing these coarse grade scratches.

⚙️ Adapting your process for today’s ultrafine metallics.

Basecoat metallics are finer than they’ve ever been, requiring a finer and very consistent scratch profile. Technicians today are having to sand finer than they ever have before. Too deep of a scratch, improper removal of paint build up, or even inadequate removal of dust on the panel could all impact the quality of the job.

✔️ Strive for a uniform, flat finish with even scratches.

✔️ Hand sand with a flexible abrasive and apply light pressure around curves, body lines, and arches.

✔️ Double check paint company recommendations for exact abrasive grade before DA sanding (typically 800-1000 or finer).

⚙️ The risks of “covering up” vs. avoiding all together

Pigtails may start to appear on a surface during the sanding process as result of a variety of factors. Sandpaper loading, incorrect grit selection, and inconsistent sanding techniques (uneven pressure or sanding pattern) are some of the main reasons why imperfections may result.

✔️ Do not use abrasive past the life of the disc, avoid loading or clogging.

✔️ Dust extraction solutions can help remove dust and contaminants that contribute to loading.

✔️ Use the correct grit sequence before transitioning to finer grades too quickly.

Failure to address or avoid these types of sand scratches, could lead to possible rework or a complete repaint of the panel. 

Body Repair

Cut through the complexity of today’s vehicle repairs. Choose high-quality abrasives and tools that can help drive productivity throughout your process. Proper body work and prep is the foundation of a quality paint job.

Metal warping during body work.

Avoid sanding metal too long that could lead to weakened metal. Unwanted jagged edges and burrs could also appear without a clean, precise cut.

✔️ Get the job done with:

  • 3M™ Cubitron™ 3 Cut-Off Wheels
  • 3M™ Cut-Off Wheel Tool

Structure damage caused by weld removal process.

Using a file belt instead of a drill can help with faster removal of welds, limiting the chance of any additional damage to the substrate or inner structure of the vehicle.

✔️ Get the job done with:

Paint Preparation

Speed, performance, and consistency are all factors to strive for in shop process and abrasives. Consider the use of dust extraction to help boost productivity by helping to reduce rework and cleanup time. With the right tools, processes, and resources, vehicles get to the finish line faster.

Deep inline scratches while sanding filler.

Identify and remove scratches whilst working upwards through the grades. Be sure to remove all coarse grade scratches before spraying primer.

✔️ Get the job done with:

An inconsistent scratch profile during blend panel prep.

Use a combination of hand sanding and DA sanding to achieve a uniform finish with even scratches, especially when spraying complex metallic colours.

✔️ Get the job done with:

Unwanted pigtails during surface prep.

It is important not to use an abrasive past the life of the disc to avoid clogging or loading. Failure to keep the surface clean can introduce dirt and other contaminants.

✔️ Get the job done with:

Paint Finishing

Mishaps happen along the way and that’s okay! When defects appear after paint, and they often do, it is a visual indication that the vehicle has been repaired. Many times, remediation or paint correction is necessary, aimed to match the texture originally put in from the factory.

Matching factory orange peel after paint.

Sanding with 1500 or 2000 grit abrasives with an optional Paint Finishing interface pad, can help flatten some of that unwanted texture. Get the job done with: Keep a close eye on the vehicle’s adjacent panels to ensure you are matching the texture originally put in from the factory.

✔️ Get the job done with:

Removing dirt nibs in paint.

Knock down the nibs seen on the panel with a 1500 or 2000 grit abrasive on a small or tilted DA sander. Blend the surface to avoid having any flatter spots where the defect existed that could stand out later on.

✔️ Get the job done with:

Please always consult national regulations for suitable Personal Protective Equipment (PPE) for use against hazards, including isocyanates.

For additional information, including important safety and warranty information, regarding 3M Automotive Aftermarket Products, please visit: www.3m.co.uk/aad-info

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