Priming Resin Models

Angus6619 · Post by **Angus6619** » Tue Mar 15, 2011 2:50 pm

I've done a few searches here, but found conflicting answers.

I've been into modeling for years and have always used Krylon gray primer after washing my resin (or plastic) parts in warm water + mild dish washing soap.

This has always worked well for me, but my latest resin kit - a 20" Battlestar Galactica Pegasus made from white resin - doesn't seem to accept the Krylon primer as well as my past resin kits.
If I scratch the back of my fingernail across the primed areas it will come off with moderate pressure.

Does anyone have any alternative primer suggestions or maybe different preparation before priming?

Malcolm M · Post by **Malcolm M** » Tue Mar 15, 2011 3:28 pm

I'm not an expert, unlike many here. But when I've had primer adhesion problems it's usually down to mold release still on the kit.

I've had resin kits that have seemed clean after washing and then it's almost like the resin is bleeding fresh mold release. Usually a scrub with Simple Green cleans the remainder off.

However sometimes that doesn't work.

I bought the Coneheads ship and the mold release laughed at the Simple Green. It took an old toothbrush and Comet scouring powder to finally get it off.

Angus6619 · Post by **Angus6619** » Tue Mar 15, 2011 4:09 pm

Thank you for your reply and suggestions.

I'll try cleaning the parts more thoroughly before attempting to prime them again...

Angus6619 · Post by **Angus6619** » Wed Mar 16, 2011 5:26 am

I washed several other parts from the Pegasus kit with soap/water followed by a good dose of Comet. Primer adhered very well after drying the parts.

Thanks again Malcolm!!!

kenlilly106 · Post by **kenlilly106** » Wed Mar 16, 2011 11:33 am

I've had a few resin kits that I've had priemr not stick, I'm fairly certain that all of the mold release is off yet the paint scrapes off like in your test.

Looking at the surface it was nearly glass smooth, I don't think the primer could bond to it. I did the Comet+toothbrush trick and it worked, gave the primer some "tooth" to grab the surface.

Ken

Mark Yungblut · Post by **Mark Yungblut** » Wed Mar 16, 2011 11:46 am

Wipe the entire thing down with laquer thinner. Just don't soak it...

Scrubbing with Comet cleaner is a ggod idea too. Apply it with a toothbrush and the grit will produce a nice tooth in the resin for the primer to stick to...

Mark

nurturer · Post by **nurturer** » Fri Mar 18, 2011 10:47 am

Sometimes I will sand over a resin model to prep it for priming with a low grit sandpaper, ie, 600 grit. Maybe even 800. Enough to 'sand away' the release for the resin. And, you prep the resin 'skin' to receive the primer with more adherence.

Malcolm M · Post by **Malcolm M** » Sat Mar 19, 2011 12:10 am

Angus6619 wrote:I washed several other parts from the Pegasus kit with soap/water followed by a good dose of Comet. Primer adhered very well after drying the parts.

Thanks again Malcolm!!!

My pleasure, glad it worked out.

kenlilly106 wrote:Looking at the surface it was nearly glass smooth, I don't think the primer could bond to it. I did the Comet+toothbrush trick and it worked, gave the primer some "tooth" to grab the surface.

I've had kits like that. You look at the bare resin shining because it's so smooth and you think "primer won't key to that...hellooo comet!".

E-Dub · Post by **E-Dub** » Mon May 23, 2011 10:07 pm

Belt and suspenders, folks. Try comet (Heck, try cupid, donner and blitzen, too) Orange clean, isopropyl alcohol.

Harry Joy · Post by **Harry Joy** » Tue May 24, 2011 7:35 am

I'm a big propenent of using rubbing alcohol for all sorts of modeling tasks, and I use it to clean plastic all the time, but it's not ideal for resin. Alcohol just can't seem to cut it cleaning resin, and dishwashing fluid doesn't do it either. I usually use stronger cleaners like Castrol Super Clean or Formula 109 for resin.

E-Dub · Post by **E-Dub** » Mon Jun 06, 2011 3:59 pm

I use the rubbing alc to clean off any residue from the other cleaners.

AbsoluteSciFi · Post by **AbsoluteSciFi** » Wed Jun 08, 2011 6:26 pm

Lots of good advice here, but there are several things that clean the surface really good... detergents, for one, I have mentioned why in another thread; I tell about the "diode" and how it works. (http://www.starshipmodeler.net/talk/vie ... hp?t=91861) Comet is a detergent + a peroxide which acts like bleach, but that part of cleaning is purely for disinfecting, and whitening.

Any degreaser will benefit your cleaning process, and detergents are considered to be encapsulation cleaners, which act in conjunction with higher alkalinity.(higher alkalinity helps to lower the surface tension making its easier to remove things from a surface)

I hear a lot of people say alcohol works good, but they don't seem to know why. Alcohol works because it is very viscous and has a super soft effect on water. It "pulls" the oil off the surface, but you need to rinse it completely away or otherwise remove it by giving it a better thing to bond with, such as a paper towel. Detergents make it so that the grease WONT rebond to the model but be take with the water. Following by alcohol will make the surface more receptive to paint, as it strips ions from the surface.

Sanding the surface of the model is a good idea for the simple reason that you are making micro scratches in the surface for the paint to latch onto.