Automotive Paint Fish Eyes – How To Prevent And Fix Surface Defects

ByJim Boslice Metalworking & Fabrication

Automotive paint fish eyes are small, crater-like holes that form when contaminants like silicone, oil, or wax repel the wet paint. You can prevent them by thoroughly cleaning the surface with a high-quality wax and grease remover before spraying.

If they appear during painting, stop immediately, let the surface dry, sand it smooth, and re-clean the area before applying a new coat.

You have spent hours sanding, masking, and prepping your project car, only to pull the trigger on your spray gun and see tiny, circular craters forming in the fresh color. It is the most frustrating sight for any garage DIYer, but it is a common hurdle when learning to spray automotive finishes.

We are going to break down exactly why these defects happen and how you can stop them in their tracks. Whether you are working in a professional booth or a humble home garage, understanding the root cause is your ticket to a mirror-like finish.

By the end of this guide, you will have the knowledge to prep your workspace, choose the right solvents, and tackle your next paint job with total confidence. Let’s get into the shop and clean up those surfaces for a professional result.

Understanding why automotive paint fish eyes occur

At their core, automotive paint fish eyes are a surface tension issue. When a tiny particle of a low-surface-tension material—like silicone, oil, or even floor wax—sits on your panel, the paint refuses to flow over it.

Instead, the paint pulls away from the contaminant, creating that dreaded “crater” or “volcano” look. It happens most often when you are using spray equipment in a space that hasn’t been properly isolated from common household chemicals.

The most frequent culprit is aerosol spray products. If someone used a silicone-based lubricant or furniture polish anywhere near your garage, those microscopic particles can drift through the air and settle on your freshly prepped metal.

The importance of proper surface preparation

Prevention is always cheaper and faster than fixing a mistake after the clear coat is already on. You must treat your surface prep like a surgical procedure if you want to avoid automotive paint fish eyes.

Start by washing the vehicle or part thoroughly with a dedicated automotive degreaser. Avoid household dish soaps, as they often contain moisturizers or additives that can leave a residue behind.

Once the surface is dry, use a high-quality wax and grease remover. Use the “two-rag” method: wipe the surface with a wet rag soaked in the solvent, and immediately follow it with a clean, dry microfiber cloth before the solvent evaporates.

How to troubleshoot your air supply

Sometimes, the contamination isn’t coming from your garage air, but from your own tools. Your air compressor is a common source of oil and moisture that can ruin a paint job.

If your compressor is older or has not been drained recently, oil and water can make their way through your air lines and into the spray gun. This will cause craters that look exactly like silicone-based defects.

Install a high-quality moisture trap and an oil separator at the point of use on your airline. Drain your tank every single time you finish a project to keep the internal air quality clean and dry.

Handling automotive paint fish eyes during the spray process

If you are mid-spray and notice these little craters appearing, do not try to “cover them up” by spraying more paint. This will only make the problem worse and lead to a thicker, harder-to-sand mess later.

Stop spraying immediately. Allow the paint to flash off or cure according to the technical data sheet of your specific product.

Once the surface is hard enough to handle, scuff the area with fine-grit sandpaper—usually 600 to 800 grit—to level out the craters. Clean the area again with a wax and grease remover, ensuring you get into the edges of the repair, and then proceed with your next coat.

Using anti-silicone additives safely

If you are working in a less-than-perfect environment, you might consider using a “fish eye eliminator” or anti-silicone additive. These are chemicals you mix into your paint to lower its surface tension.

Think of these as a safety net, not a replacement for good prep work. They help the paint flow over microscopic contaminants that you might have missed during the cleaning process.

Always follow the manufacturer’s mixing ratios precisely. Adding too much can cause other issues, such as poor adhesion or a loss of gloss in the final finish.

Common mistakes that lead to surface defects

Even experienced woodworkers or metalworkers who are new to painting can trip up on basic shop habits. Here are a few things to watch out for:

  • Hand oils: Touching your sanded surface with bare skin transfers oils that will cause craters. Wear nitrile gloves at all times.
  • Compressed air hoses: Using old rubber hoses that have been used for pneumatic tools previously lubed with silicone.
  • Contaminated tack cloths: Using a low-quality or old tack cloth that has picked up dust or grease from a dirty workbench.
  • Poor ventilation: Letting overspray and contaminants linger in the air where they can settle back onto your wet project.

Frequently Asked Questions About Automotive Paint Fish Eyes

Can I fix fish eyes after the clear coat is fully cured?

Yes, you can, but it is labor-intensive. You will need to carefully sand the defect flat with a small block and high-grit paper, then buff and polish the area to restore the shine. If the crater is deep, you may need to spot-paint the area before clearing it again.

Is it possible that my paint is just defective?

It is very rare for modern automotive paint to be “defective” in a way that causes fish eyes. 99% of the time, the issue is environmental or related to surface prep. Always check your mixing cups and stirring sticks for contaminants before blaming the paint brand.

Do I need a professional booth to avoid these problems?

You do not need a professional booth, but you do need a clean, controlled environment. A makeshift booth made of plastic sheeting can work wonders by keeping dust and airborne particles away from your project.

How do I know if the contamination is in my air line?

A simple test is to spray a piece of clean cardboard or glass with just air from your gun. If you see tiny droplets or spots forming, your lines or compressor are contaminated. You will need to flush your lines and check your filters.

Final Thoughts on Achieving a Flawless Finish

Mastering the art of automotive painting takes patience, but solving automotive paint fish eyes is all about disciplined preparation. Treat your workspace like a clean room, be obsessive about your cleaning routine, and always keep your air supply dry.

Don’t let a few craters discourage you; every pro painter has dealt with these exact issues at some point in their journey. By following these steps and keeping your process consistent, you will spend less time fixing mistakes and more time admiring your hard work. Keep your shop clean, keep your tools maintained, and keep building!

Jim Boslice
Latest posts by Jim Boslice (see all)

Similar Posts