Paint problems on a non-scifi-subject

[darth_daniel]

Hi everyone,
my brother is building a 1/24 Tamiya Porsche 911 GT2 kit and is becoming more and more frustrated as he can´t manage to achieve a satisfying paint job on the car´s body, while the rest of the car is pretty much finished. Some dark dots came out of the airbrush while spraying the clear coat, so he had to wetsand some spots, and when he shot those spots with paint again, this happened:
1 2 3 4 5

After sanding again, the same thing occured again. Can anyone tell me what causes those strange "engravings" and how to avoid them? It seems the edges are where the paint untouched by the sanding paper (previous paint layer) starts. Could polishing solve the problem? The whole body has an orange peel, so he´ll have to polish the body anyway (at least I´m trying to convince him to do so as he doesn´t want to invest that much work ).
Many thanks in advance for any advice!

[TER-OR]

Was there some sort of engraving beneath?

It seems the paint may be too thick, both the paint itself and the layer you're applying. The car guys will paint layers and buff between coats. At least some of them do.

Also, the PolyScale Plastic Prep has been a staple for me, it seems to cut all the plastic surface tension, and inhibit static charge.

[Joseph Osborn]

What paint chemistry is in use here? It looks like the paint isn't cured. With that heavy texturing, I think I'd strip the whole thing and start from a good primer base. Wet sanding between light coats will help, too. If nothing else, he can try a flat basecoat, wet sand, and then a clear gloss topcoat. That'll help to minimize the texturing. And clean out that airbrush before spraying the clear

Gloss paint = ugh

[darth_daniel]

Thanks for the replies. My brother is using Tamiya acrylics. I already assumed the previous paint layers might not be cured sufficiently, though he waited a week between each coat. Maybe the airbrush is to be blamed, as it´s a very basic Revell airbrush. For some reason he wants to use this one although he could borrow my Badger 360.
What I don´t understand though is why those "engravings" run like an edge around the area where he wetsanded.
Anyway, thanks for the replies and advice!

[Kylwell]

Possibly becasue the clear coat wasn't fully cured and the edgs built up a ridge. Possibly becasue he didn't fully feather the sanded area.

[kenlilly106]

Looks like there was a rough spot under the gloss paints, and the paint didn't completely fill in the rough spots.

Or else something reacted along the way at the edge of the sanded paint/gloss coat, hard to tell

Honestly, I'd strip it all off and restart from a nice clean base. If this problem has already happened, trying to fix it may cause the same problem to show up at other places or in the same place again.

Ken

[DX-SFX]

Ditch the model acrylics.

Strip the airbrush and clean it meticulously.

Strip the car body.

Spray with a white plastic primer like Duplicolor or similar i.e. real car paint, thinned with a little cellulose lacquer thinner and apply with the airbrush.

Spray with your chosen Duplicolor colour thinned with a little cellulose lacquer thinners and apply with the airbrush.

Polish.