How to Fix, Sand and Polish Spray Paint




Introduction: How to Fix, Sand and Polish Spray Paint

We all make mistakes by being hasteful :)

So, I've been working on the final stages of the center channel stand I'm making for my Definitive Technology CS-8080HD center channel unit and I paid the price by rushing. My garage was very cold when I was painting the metal, which caused a couple of problems with the Rustoleum spray paint I was using. Here is how to fix those mistakes (hopefully you won't make them in the first place).

Sand and repaint sagging paint surfaces

When you apply spray paint too fast, too heavy, too cold of a climate or too humid of an atmosphere, you can get sags in your paint. This occurs because the underlying layers have not fully flashed, which means the solvents in the paint have not had a chance to reach the surface and allow the paint to dry. Therefore, new paint layers hang on subsequent wet layers and gravity does the rest to pull the paint down the vertical surface. Here I'll show you how to sand down the sags to a smooth surface and then repaint.

Sanding and polishing clear coat overspray

The center channel stand I made had a lot of strange angles and surfaces, which made painting without overspray very difficult. Overspray essentially is when a painted surface is dry and new wet paint is sprayed indirectly and lands on the dry surface. The result (especially with a clear coat) is a dull and speckled surface rather than a smooth glass finish. I'll show you how to sand and buff the clear coat back to a shine

Step 1: Wet Sanding Rough and Sagging Paint

When I wet sand, I like to add a few drops of soap to the water in order to allow the sandpaper to glide more easily over the surface and not grab as easy, biting into the paint. I used 3M 600 grit wet sanding paper to make small circles and knock the bumps down. Every now and then I'd dry off the surface to see how it looked. The goal is to try and not go beyond the primer layer.

Step 2: Repainting Sagging Paint Surfaces

This step is pretty standard since you'll simply follow the same steps you did the first time you painted, which can be found on the back of the can you're using. They typically look like this (varies among manufacturers):

  1. Be sure your surface is clean and dry (remove all contaminants)
  2. Use only when temperatures range between 50F and 90F where relative humidity is below 85%
  3. Begin and finish spraying off the object using a side-to-side sweeping motion, overlapping your spray slightly with each pass
  4. Paint can be recoated within an hour
  5. Paint fully cures in 24 hours

Step 3: Lightly Wet Sand and Polish Clear Coat

If your project has any orange peel (not quite perfect mirror finish), you might want to bring out the shine with the use of some wet sanding and machine polish. This is also a good step if your project retains some overspray from previous spray paint applications. In my case, I had so many overlapping spray angles, that the mist from the clear coat spray settled on a dried surface and made it dull. Wet sanding and polishing will get rid of that as well.

The important thing here is to go slow and not burn through the clear coat. You can always try another round of wet sanding and polishing, but once you hit the base coat, you've got a problem and need to repaint.

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    3 Discussions


    2 years ago

    An interesting article giving a detailed account on how to fix and polish spray paint. In order to avoid any further sagging or peeling of the paint, you could consider ceramic pro coats for the surface protection of the car. DRM Motors is one such service centre that can assist you in getting the painting done. Their service centre provides end to end services in terms of painting, polishing, repairing modifying, and maintaining the vehicle. Their experts do a fine job and thus have many satisfied customers.


    2 years ago

    Thanks for the article. How long do you have to wait for the spray paint to cure enough to start wet sanding?

    Technically Fun
    Technically Fun

    Reply 2 years ago

    Regular primer can be wet sanded after about 10-15 minutes. Colors take a little longer. I'd wait at least 30 minutes, if not an hour before wet sanding any spray paint colors. I would not recommend dry sanding. Also, be sure to add a pump or two of liquid soap in your water bottle to help glide over the surface. This will ensure you don't put too much lateral stress on the paint layer.