Previously sanded off details come back after clear coat...

[Jamese30]

Hi All

On my Sunbeam kit I sanded off some Tiger decals to turn my Tiger into an Alpine. I sanded, primed, sanded and primed again until the detail had all gone. They were still not visible after the base coat of Tamiya paint had been applied and dried (3-4 costs) but then after the automotive clearcoat was applied and dried they reappeared as a silhouette.... visible in some lights.

I'm guessing my lacquer is a bit "hot" and has pulled the paint down.

 

Any ideas????

 

James

Edited 1 hour ago by Jamese30

[peteski]

Yes, "ghosting" can be a problem.  As I understand coating the sanded areas with liquid cement (basically melting the plastic surface back into solid state) BEFORE priming and painting will prevent this from. But that isn't much help to now.

[Bainford]

This phenomenon is called 'ghosting'. It is quite common when using 'hot' paints over sanded-off body features. 

Though I haven't tried it, I have heard that painting on a layer of thin liquid model cement over the sanded surface before final sanding and primer can prevent this from happening.

[sidcharles]

agent #99 . . .

[LOBBS]

Ambroid Proweld or a similar hot solvent glue brushed over any details like that will make them "pop" again and you can resand them smooth for good. Kinda like taking a damp rag to woodwork to make the grain stand up before laying down your stain and varnish.

[SpeedAndViolence]

Not even a primer/sealer will work? I thought that was the whole point of using a sealer? 

[LOBBS]

9 minutes ago, SpeedAndViolence said:

Not even a primer/sealer will work? I thought that was the whole point of using a sealer? 

"Ghosting" occurs due to stresses in the plastic from the injection molding process. The hot solvents, whether from using a glue before painting or from a hot paint, relieve some of that stress causing the sanded off details to rear their ugly heads again. 

[Straightliner59]

Zinsser BIN will definitely help. Apply it under the primer.

[Chris V]

"Ghosting" is a common phenomenon caused by differences in the density of the plastic from the injection molding process:

As the molten plastic cools from the outside, microscopic pores form towards the centre of the part. By trimming/sanding off bodywork details, you expose material that was originally further from the outer surface and thus more porous/vulnerable to solvents in the paint than the immediate surrounding area.

By giving the area a gentle wash of liquid cement you essentially saturate the porous plastic with solvent and binders, causing a controlled "collapse" of the area prior to paint. This allows you to fill in any cavities left as the cement evaporates and sets. Always allow the plastic ample time to thoroughly dry and set before proceeding with the surface preparation and paint.

The severity of the ghosting varies a great deal depending on the type of plastic and the paint you use. Some automotive type lacquers contain highly volatile solvents, and in some cases ghosting can even happen on surfaces which have been thoroughly prepared:

 

Edit: These images illustrate one of the most extreme cases of ghosting I've ever experienced. The surface had been meticulously prepared, using the liquid cement method described above, and then left to cure for several months. However in this case the unusually "hot" solvents in the lacquer (Zero Paints automotive lacquer basecoat) were able to penetrate the primer and react with the brittle old sixties' plastic underneath. 

Edited 2 hours ago by Chris V

[bobss396]

I've had ghosting happen MONTHS after paint/clear was applied. Too many solvents too soon.