HELP!Melting paint....

[Too Bo Coo]

Hey All!

I'm having a strange problem. I have recently painted up some 1:64 Hotwheels cars for Car Wars/Dark Future
I applied the paint in the following order.
1: Base layer of primer is the enamel from Hotwheels
2: Black GW primer
3: Black drybrush
4: Detail painted with Army Painter paints.
5: 'Brush On' Army Painter 'Dip' Dark Tone.
6: Micro Set/ Micro Sol with decals
7: Army Painter matt coat
8: weathering with 3 Vallejo paints
9: AP matt coat again.

Now, at step 7 & 9 I noticed that the undercoating was 'melting', but it was not uniform, and since I'm painting for Post Apoc, it worked out. But I'm not clear why this happened.  Once the Matt dries, then it's fine to touch, but the 'cracking' is evident....

Does anyone have any ideas??  Thanks!

[Lordblackwing]

It's possible that the matt coat is reacting with the MicroSol. I'm not familiar with the Army painter matt coat,is it an enamel or  laquer base? If laquer base, it may be melting through due to the solvent base used to make the laquer sprayable. I have had this problem with certian brands of inks melting when sprayed with Dullcoat in the past. Hope this might helpsolve the issue.

[Za Zjurman]

Did you wash the car before painting? It is possible there was some grease on the model (from fingerprints etc.). It happened to me once. The paint seems to let loose at these spots. Next time give the model a wash in some warm water with a little washing up soap (Dreft   ).

Regards
Za

[snitcythedog]

Once the Matt dries, then it's fine to touch, but the 'cracking' is evident....

Have you used the same painting techniques on plastic or on clean metal?  I would be interested to see if is the Micro Sol reacting with the army painter dip creating an impromptu crackling medium. 
My first inclination though is that the GW primer is not adhering to the factory clear coat on the Hot Wheels.  I always strip the die cast cars to get rid of anything that might cause my paint to flake and so I get clean details when I paint them up.  I don't know if that helps, but that was my two cents. 
Snitchy sends.