3

I was trying to paint my bare chromoly steel bicycle frame and fork. I sanded the frame and fork with 120 grit sandpaper to give it a slightly rough surface for the paint to adhere to. I used a quick-drying acrylic rattle can spray paint to apply primer to it.

I waited for more than 24 hours to apply the top coat (same brand and paint type). I stuck masking tape to check if the primer would come off, it didn't. I applied a little too much of the top coat so there were runs on some parts of the frame. I tried wiping the runs with a rag thinking that only the top coat would be wiped off. Unfortunately, when I wiped it off, the primer went with the top coat.

Is that supposed to happen when I wipe off a fresh top coat? I'm not sure if the metal was still too smooth for painting but it is scuffed. Also, for runs, if I can't wipe it off, do I just wait for it to dry and sand to smooth out the surface and then reapply another layer of top coat?

By the way, these are the instructions on the can: enter image description here

It doesn't say how long the paint dries

  • 1
    Not knowing exactly what you used it is my guess that the solvent from the topcoat softened the primer. Did you follow the directions on the can for the primer? As far as runs go practice your technique to minimize them. Then sand them smooth after they cure and respray a topcoat. – mikes Dec 18 '16 at 19:48
  • 1
    While no expert, I think there are several errors here. The first was the sandpaper - 320 grit is the coarsest I've heard of people using, and going in stages to 2000, or even 3000. The second is applying way too much paint in each coat; many thin coats produce a better outcome. The third is incorrect timing between coats. Read the instructions on the can carefully, then follow them to the letter. In particular I guess you didn't wait long enough between coats. Nate says it's 90% prep and 10% skill. The skill part is 90% patience. – andy256 Dec 20 '16 at 3:48
  • @andy256 yeah, I've read that around 300-400 grit would do it but I just tried scuffing the surface and when I tried that with 200, I couldn't feel the that the metal was rough enough for the paint to stick so I tried 120. – dork Dec 20 '16 at 7:54
5

As mikes indicated, the chemicals in your top coat reactivated your primer coat, much like if you were to write something in sharpie, it is dry to the touch, but if you were to wipe alcohol over it it would smear.

I use aerosol cans for a lot of different types of painting, and unfortunately drips are often impossible to remove without a lot of sanding or starting over. The best method is to avoid them in the first place with good technique. I realize this sounds a bit arrogant but correcting them often leads to more issue and the clear coat not laying smooth.

You can wait for them to dry, sand the entire area or tube smooth and start over. Don't only sand the area of the drip or you will get an uneven surface.

As they say in the autobody world, paint is 90% prep and 10% skill. When using rattle cans it also helps to let the cans sit in warm/hot water for several minutes before use. This allows the internal temp to rise and allows the paint to atomize more efficiently. You may also find "artists" paints used for graffiti murals don't drip as easily and they are very heavily pigmented and a bit thicker paint. Brands as an example would be, Belton Molotow, Montana, Loop, and Flame amongst others.

Also when sanding large areas or tubes, you should not hand sand as your fingers push at different pressures making the sanding stroke uneven, this can be remedied by using an electric sander, block or something similar, ive also found for round tubes a thick cloth or towel behind the strip of sand paper works well for pulling around a circular shape, the cloth helps prevent the sandpaper from tearing and gives nice even pressure.

Good Luck!

  • 2
    Further to nate's points. Cheap spraypaint sucks - spend a bit more. Avoid fixing runs by not making them in the first place. More thinner coats works better than heavier coats. Don't be surprised if you can still see through the first two-three coats. Good things take time. Use a higher grade of sandpaper too, 120 is quite coarse. Lightly sand between coats too. – Criggie Dec 20 '16 at 0:06

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.