I applied a coat of epoxy as a clear coat with a bristle brush:
The coating looked smooth at first, but then these bubbles appeared. I can't tell if they are from air trapped in the top layer of exposed fiber, or if the surface was dirty, or if dust trapped in the top fibers was breaking the surface tension of the epoxy.
Dragging the brush over the epoxy seemed to eliminate them, but new bubbles would appear. I tried to use my finger (in a nitrile glove) to squeegee the epoxy into the pockets and hold the surface smooth, but same problem... the bubbles would resurface. Warming the epoxy with a heat gun didn't seem to have much effect.
The bubbles are not originating from the epoxy or the application: I'm not foaming the resin. The bubbles seem to be generated by the substrate; either through out-gassing or a contaminant that is breaking the adhesion or surface tension of the epoxy.
Could the surface of the frame be simply too porous? Did I not sand it smooth enough?
Did I not allow the surface to dry long enough? Was the alcohol not fully evaporated?
This was the final surface finish over at least 50% of the frame.
After cure, I sanded the bubbles out.
At this point I applied another coat of epoxy. Small disaster: I did not sufficiently clean the sanding dust out of the remaining holes in the surface. So, the second coat of epoxy entrapped small white dots into the finish.
Forgot to photograph these white specks, sorry.
AND the second coat of epoxy still produced bubbles. I am thankful they expressed to a dramatically lesser degree. Here is what the second coat looked like (sanding of the frame in the background, I was so mad at the finish that I neglected to document the progress). Bubbles, but not as many. This is also after a light sanding with 800 grit, so the luster is matted.
Searching online for methods to remove the clear coat bubbles, I ran across this video:
Note he warns not to sand the bubbled finish because it will force the sanding dust into the holes. I wish I had searched for this earlier. So I took a razor to my whole frame removing the bubbles and white entrapped dust specs. Some areas I took the clear coat off completely down to bare fiber.
From here, I need to re-assess the situation. I cannot simply repeat the same clear-coat process because the same problem will certainly also repeat. Options... which I should try on a small test section of the frame:
The coating looked smooth at first, but then these bubbles appeared. I can't tell if they are from air trapped in the top layer of exposed fiber, or if the surface was dirty, or if dust trapped in the top fibers was breaking the surface tension of the epoxy.
Dragging the brush over the epoxy seemed to eliminate them, but new bubbles would appear. I tried to use my finger (in a nitrile glove) to squeegee the epoxy into the pockets and hold the surface smooth, but same problem... the bubbles would resurface. Warming the epoxy with a heat gun didn't seem to have much effect.
The bubbles are not originating from the epoxy or the application: I'm not foaming the resin. The bubbles seem to be generated by the substrate; either through out-gassing or a contaminant that is breaking the adhesion or surface tension of the epoxy.
Could the surface of the frame be simply too porous? Did I not sand it smooth enough?
Did I not allow the surface to dry long enough? Was the alcohol not fully evaporated?
This was the final surface finish over at least 50% of the frame.
After cure, I sanded the bubbles out.
At this point I applied another coat of epoxy. Small disaster: I did not sufficiently clean the sanding dust out of the remaining holes in the surface. So, the second coat of epoxy entrapped small white dots into the finish.
Forgot to photograph these white specks, sorry.
AND the second coat of epoxy still produced bubbles. I am thankful they expressed to a dramatically lesser degree. Here is what the second coat looked like (sanding of the frame in the background, I was so mad at the finish that I neglected to document the progress). Bubbles, but not as many. This is also after a light sanding with 800 grit, so the luster is matted.
Searching online for methods to remove the clear coat bubbles, I ran across this video:
Note he warns not to sand the bubbled finish because it will force the sanding dust into the holes. I wish I had searched for this earlier. So I took a razor to my whole frame removing the bubbles and white entrapped dust specs. Some areas I took the clear coat off completely down to bare fiber.
From here, I need to re-assess the situation. I cannot simply repeat the same clear-coat process because the same problem will certainly also repeat. Options... which I should try on a small test section of the frame:
- Enhanced cleaning practices, full dry [heated possibly], and re-coat with epoxy.
- Dilute the epoxy to reduce the viscosity and re-apply... possibly in a spray.
- Re-apply the epoxy and mist the surface with acetone like THIS (essentially dilution).
- Use a different clear coating, like a polyurethane.
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