What exactly is the difference between a primer and a barrier/sealer? My understanding was that an automotive primer was a barrier but I just came across some information that contradicts that. Will an automotive sandable primer act as a barrier, especially over red plastic, or do I need to use a separate barrier/sealer product as well? If I do, what is a good product to use? I have heard the Floquil barrier mentioned before. Are there others out there as well or should I just look for that one? Thanks.
I don’t know for sure what the difference is in the make up of the paints but the sealer type primers go on as a smoother harder layer. The sandable primers are fluffier(for lack of a better word) and fill in small scratches and such better, especially the high build up type. Sandables are more porous by nature and chalky.
Not all automotive primers are sealers. I had forgotten about the different types of primers till recently myself. In thinking back I can remember articles in auto mags talking about the different types. Mainly for do-it-yourselfers that may be getting a vehicle ready for paint and having to do the bodywork a little at a time. If you’ve ever seen a car or truck running around with rust bleeding through the primer, they didn’t use a sealing type. It let moisture bleed through to the bare metal and start the rusting process all over again.(or maybe they didn’ t get rid of all the rust to begin with [:D], either way, it bled through)
It works both ways too. Not only does a sealer keep colored plastic from bleeding through the paint, it won’t soak up as much paint or be affected as much by the solvents in the paint so you could get away with a hotter paint without crazing the plastic.
I’ve been using DupliColor primers in a spray can and have had good luck. Over the last couple weeks I’ve started using a sealing primer once I’ve got the bodywork done and it has made a difference in coverage with the color coats. I have an older Monogram kit molded in red that I’ve been working my way up to. That plastic seems really soft and the few parts I used Testors glue on, it melted the heck out of so I’m anxious(and skeered) to see how the primer affects it. Always try something new on scrap of course…
Not a definitive answer but like Murphy’s Law states; if you’re not certain of the answer, at least make it sound convincing…[;)]
I have used Floquil Barrier to protect the plastic from melting when using a laquer type paint. Other brands may also work, but this is what I have always used…you know the old dog, no new tricks thing! Reading Wingmans reply, I realized how little I know about all this, so take it with a grain of salt.