Building Tips and technical articles. > Paint and finishing

CA ridges showing through paint top coat?

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Dennis Toth:
Guys,
Am working on finishing a top color coat over the fuse/wing center planking joint. I got the fuse in place, added some epoxy/fiberglass flower filler then used Elmer's wood filler as smooth coat. This came out very smooth, I used some CA to seal the sanded the filler by applying and wiping off. This I sanded with 400 and thought I was ready for the black color coat. I seemed to have missed getting all the CA that got wiped onto the planking area sanded totally flat. The paint is Design Master acrylic lacquer and goes on very smooth (electric don't need fuel proof). Now for the bad news. Once the paint dried there were streaks down the center planking where the CA wipe was applied. It looks like where the CA wipe went over the planking it was not totally flat. I sanded the streak area flat with a block to get it totally flat. Then after wiping down, re-sprayed the DM black. It is very nice paint and goes on very nice. BUT, when it dried there were the streaks. OK, sanded it down again and re-coat, same result. On a test piece I wiped on CA just as I did the fillet, let it kick and set for a few hours then sprayed the DM black over it, no problem.

I called Design Master customer service, which is very good. They said they never ran across this issues but admitted they didn't work with modelers that much. We discussed an option of using a primer first then top coat. I have done some test pieces and it goes over the primer with no problems. I will try this on one panel on the bottom.

Having said that has anyone had this kind of experience with any type of paint going over CA sealed surface (I know Windy used CA to seal lots of small pieces before painting with no trouble)? If so how did you solve the issue.

Thanks,   DennisT

Randy Powell:
I've had weirdness happen. Never this particular weirdness. No idea unless there is some sort of chemical reactivity going on.

Avaiojet:
Primer?

Dennis Toth:
I did the test with the primer on one section on the bottom. The primer is a universal sandable solvent based material that I have used under dope and other paints. After sand down the black DM paint to where I could not see or feel any ridges I applied the spray primer of a section that had previously had the ridges develop. The primer went on smooth with no bad reaction. Let it dry several hours. When I came back to check how it was doing a problem developed in that as the primer dried and I assume shrunk a bit it formed gaps in the film surface down to the bottom surface paint. Some places adhered well but the surface was uneven. The prep I did was to sand down the DM black paint with 150 grit dry until smooth with no ridges. Then a light sand with 400 dry. and spray area with the primer. My thought was to not get it super smooth so the primer had something to grab to.

I am working with a test piece now and trying to apply a clear coat (Diamond Clear) seal to the DM paint that can allow a smooth coat. So far the DC went on smooth, will check in a few hours to see if it can be painted over with the DM.

Best,   DennisT

Dennis Toth:
This is becoming a real pain. For something that should have been a 15 minute deal it's taking four days of time to sand, test, sand again, test. Still no clear answer. The Diamond Clear went on and dried hard but in the areas were the CA ridges were it is not smooth and the ridges are still there. For some reason the area where the CA streaks are will not seal nor will it allow a fill in to get it to sand smooth.

Best,    DennisT

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