http://www.dakkadakka.com/dakkaforum/posts/list/8.page JForum - http://www.jforum.net How necessary is it really to wash off plastic parts with soap and water before you prime them? Common wisdom says do it, so I've always done it. But is it really necessary? Anecdotally it seems that washing may really only be required for resin (finecast) type parts.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880265.page http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880265.page GMT http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880296.page http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880296.page GMT http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880297.page http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880297.page GMT http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880341.page http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880341.page GMT GW spray paint!) so that may have something to do with it? I use Vallejo polyurethane primer through an AB btw.

I do wash anything that I have stripped (to ensure the stripping agent has fully gone) and all resins.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880481.page http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880481.page GMT
I failed to wash resin once and it was a nightmare.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880544.page http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880544.page GMT http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880589.page http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880589.page GMT FW models unwashed before and got away with it, but in general it's a good idea to wash anything where release agent has been used - Resin and Metal.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880696.page http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880696.page GMT GW and other generaly not necassery.
You might want to lightly sand really smooth surfaces though as some paint and primer might not stick to really smooth surfaces and can come pealing off later. (This happened a couple of times with me mostly around the edges.)
Metal never gave me more problems then plastic.

Resin like FW I recommend hot not boiling water and some dishwash soap and leave it soak overnight. If necassery repeat but use a soft scrubbing brush on the parts that give you trouble. Be careful as not to damage you parts.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880733.page http://www.dakkadakka.com/dakkaforum/posts/preList/541979/5880733.page GMT
Cast resin (Forge World and FineCast) use a different material, the resin, that will stick to the mold, so the before casting the molds are coated in a release agent. This agent, if you do not wash it off, will be between your base coat of paint and your model. If you don't wash it off, some time down the road your paint will start coming off.
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