Ridiculously stupid question -- will glue stick to primer?

sbaxter · Post by **sbaxter** » Thu Feb 19, 2015 10:10 am

I see builds sometimes where it appears people have added parts to a kit they've already primed, and sometimes read accounts that seem to indicate some glues will adhere to primer, but I had always presumed it would not. I'm reasonably sure regular model cement wouldn't work, but what about CA and/or epoxy?

I don't mind sanding or scratching primer away from mating surfaces, but if I don't need to do so, sometimes it would make things easier ...

Qapla'

SSB

Tommy8008 · Post by **Tommy8008** » Thu Feb 19, 2015 10:23 am

From my own personal experience, I've had no trouble glueing painted parts together, even with Humbrol poly cement.

TREKKRIFFIC · Post by **TREKKRIFFIC** » Thu Feb 19, 2015 12:27 pm

Model glue or CA will soften paint causing the joint to fail. If you have a part that won't undergo much stress you can use 5-minute epoxy to glue it on without hurting the primer. Best to just scrape off the primer before gluing if possible.

Kylwell · Post by **Kylwell** » Thu Feb 19, 2015 9:02 pm

For small bits I'll glue straight to primer. Usually tho I'll sand or scrape the joint areas first to ensure a good bond.

gsb5w · Post by **gsb5w** » Fri Feb 20, 2015 7:35 pm

In my early days of model building i would often glue primed parts together and i can tell you that the bond is weak doing it that way. I still see people doing it but i dont anymore.

MillenniumFalsehood · Post by **MillenniumFalsehood** » Sun Feb 22, 2015 6:20 pm

I never do it these days. My experience tells me that if I do that I will end up with a terribly weak joint.

Tankmodeler · Post by **Tankmodeler** » Tue Feb 24, 2015 4:26 pm

Like just about everything else in this hobby, the answer is "it depends".

If you are glueing on a small part or something that shouldn't need to be held well, then any number of glues will work to hold the part to a painted surface.

If you need to part to take some knocks or some loads, then make sure you have all the paint off the surface first and this includes Mr. Surfacer.

Fundamentally, the bond between paint and plastic/resin is much weaker than that of pretty much any of the adhesives (other than white glue). If you need strength, scrape it off. The stronger it needs to be, the more unpainted surface to surface contact there needs to be.

Paul

sbaxter · Post by **sbaxter** » Tue Feb 24, 2015 5:32 pm

Okay, that was what I always thought and the way I always worked, but I had seen some people who appeared to have made it work. Sometimes it can be a little inconvenient to have to remove primer, but I guess I'll keep doing it. Thanks for the replies!

Qapla'

SSB