Primer for Testors One Coat

[MikeBoyle]

What are you using for primer under Testors one coat? I know some have shot it on bare plastic, but I have done body work that requires a primer coat to seal. My go to has always been Krylon, but I had a crazing issue with the One Coat. I know Tamiya primer will work, but there is no local source for it. I'd like to find something I can get in rattle can from a local hardware store or wally world if possible.

Thanks!

[Ace-Garageguy]

I use Duplicolor and Plasticoat sandable primers from the auto-parts stores. They come in several colors...gray, black, red oxide and white. High-build versions of some of them are also available.

The problem is that they're pretty hot for today's styrene-kit material. They will often craze the surface of bare plastic (if shot wet, especially) but letting them dry thoroughly, sanding with 600-800 grit, and re-primering as necessary will kill the crazing, and give you a very good base for your color.

This is Duplicolor light gray over some heavy bodywork, including a scale 3" top-chop.

Finished car, shot with Testors "one coat" (it took 5 coats of color and 3 of clear).

[Ace-Garageguy]

I use Plasti Kote T-235 Sandable gray primer no matter what type of paint I plan on using. It also comes in red oxide and white... It's also safe to spray over any styrene... I've used it on kits fifty-four years old with no problems. I buy mine at the local parts house.

A little more information here might be useful. Many styrene kits from from 50+ years ago (I'm currently working on a 1961 Johan Mopar original issue) were made from plastics that were MUCH more chemical-resistant than today's cheap-as-possible goo.

The old Johan kit-plastic is so tough, it will withstand SEM self-etching primer with NO crazing whatsoever, but the same stuff would ruin a current Revell '50 Olds kit.

Speaking of which, the Revell '50 Olds I have going on another thread (and just painted the hood on) is getting primered with Plasticoat, as a back-to-back experiment compare / contrast with Duplicolor primers.

I shoot my primers medium-wet to full-wet, in order to get good flow and leveling (and avoid lots of coats and sanding). Shot medium-wet over BARE plastic, the Plasticoat WILL CRAZE THE REVELL PLASTIC.

But as Plowboy says, once the primer is dry through, it makes an effective barrier under any paint. It's important to watch what you're doing, however. IF YOU SAND THROUGH YOUR PRIMER and have a bare-plastic spot, you'll need to get more primer on it to avoid possible local crazing from topcoats.

Edited August 10, 2014 by Ace-Garageguy

[MrObsessive]

While some fellas have had success with no crazing using Plastikote and whatnot, I'd strongly advise using a barrier coat before applying any paint on today's bare plastic. As Bill mentioned the older kits withstood a lot of harsh paints without crazing, but if you're building anything molded after 2004 or so, you're asking for trouble if you're not using a barrier coat.

I like Future for smaller parts, and while I use to use this for bodies, this is my go to barrier coat for those................

This has to be applied using an airbrush, but I've painted the model below in really hot automotive paint from the local paint jobber, and there's not a crazing section to be seen.

Ever since there were howls of protest about 10 years or so ago when Revell came out with the then new 2005 Mustang kit (and '06 Dodge Magnum Wagon) due to crazing, I've been a big believer in barrier coats for all paint jobs on new kits. Interesting enough, I remember Revell saying that they couldn't duplicate the problem with the complaints they were getting. I saw for myself however folks' models looking pretty bad from crazing when years earlier that was not a problem except for the very hottest of paints.

Just the appearance of today's plastic to what was molded in the '90's, one can see the difference. The plastic has a "soft" feel to it, and is obviously not as dense as in years past.

Hope this helps!

[MikeBoyle]

Thanks for the advice. Gary, is it necessary to thin the Zinsser and if so what do you use?

[MrObsessive]

You can use Isopropyl Alcohol to reduce the BIN. At least that's what I used to thin mine down with no issues. I do recommend using an older airbrush if you have one. I use my tried and true Badger Crescendo for jobs like this. It's not an outright necessity for an old airbrush------I just don't want to use my nice and fairly new Badger Patriot!

[MikeBoyle]

Thanks again. Unfortunately I only have one air brush so I may have to steal one of my friends extras or hold off on the zinsser for a while.

[Ace-Garageguy]

If you're careful with the Plasticoat or Duplicolor primers, and let the first coat flash off very well before adding additional coats (and don't ever pile it on, especially if you've broken through to bare plastic), you should be able to work without the barrier material.

To get a feel of how these primers will work, I strongly recommend you spray the backsides of parts (that won't show) on each model you're working on. Some plastics, even from the same manufacturers, are more sensitive than others.

Experimentation and practice on what YOU'RE building is the only sure-fire way to get good results.