Question: Proper surface preparation for resin bodies?

[clowncar]

After a couple of years of staring at my little stash of resin Germanica in blind animal terror, I've decided I should take a stab at finishing one or two of the forlorn things this coming summer.  Cutting out vacuformed clear parts aside, the most intimidating aspect, for me, is getting nice paint on the body shell.  I think I can apply a fairly smooth coat of paint.  But:  Is there a definitive guide to proper surface preparation for painting resin bodies?  Specifically, what grits to start with, use, and not use, and how and with what to clean/wash prior to painting?  And, do different manufacturers' resins need different treatment because of varying softnesses, willingness to let paint adhere, or just plain simple chemical off-gassing cussedness?

i've got little resin roller-skates from Herb Deeks, Model Factory Hiro, DDP Models, and Fernando Pinto all staring me in the face, if that makes a difference.  All 1/24th scale.

[tatocorvette]

As a general rule, you want to make sure the resin is clean. If it still has any mold release agent, nothing short of nuclear fusion will stick to it. Years ago I used Westley's bleach white (white wall tire cleaner). After the resin is clean, I usually sand it with 400 grit to roughen it just a bit. After that, your favorite primer can be used. The primer will tell you if there is a contaminated or soft spot as it will not adhere properly. I once had a resin body that had a soft spot in the middle of the hood. Nothing worked and at the end, I did a recess cut and filled with putty. It was that stubborn. But generally the same rules apply: Clean surface, smooth primer etc.
Hope this helps!

Thanks,

[clowncar]

Ooohhh.... Degrease first, then sand?  Very interesting!

[tatocorvette]

Yes. If you do it the other way around you risk spreading the contamination.

[clowncar]

Makes perfect sense, in retrospect. Merci!

[robhart]

Don't use acetone to degrease. I dissolved some aftermarket parts a few years ago by soaking them in acetone.

[clowncar]

A thousand years ago, I briefly worked in QC in the plastic extrusion industry. Our destructive examination protocols involved gallons of acetone. Wasn't aware it might affect polyester resins, though. Note made. Merci beaucoup!

[4wheels]

Brake fluid as a stripper for resin is a no-no as well. And yes, always clean first! Sanding first can drive the release agents into the resin, making it harder to get clean. A good automotive lacquer primer is always a good idea, too. I've used Tamiya with good success as well.

Brian

[2whl]

I've used Wesley's Bleche-White in the past. But recently for my MFH resin, I've been soaking the pieces in Polident. I also use Tamiya primer almost exclusively

[clowncar]

Polident! I'm getting really good Dos and Don'ts, here.

Thank you all, and please keep 'em coming.