Weathered detail on top of enamel paint

[Washnugget]

A question for you veterans on how to apply weathered detail over enamel paint. I've decided to use Colourcoats enamel paint on my USS Indianapolis model. I read acrylic varnish can be applied over the enamel so it protects the paint from rubbing away when applying enamel based weather effect paint. Is that the right way to do this? I'd hate to have a nicely painted ship only to screw it up when adding the weathered detail effects at the end.

[spejic]

You need to wait a while before painting acrylic on top of enamel - at least a week, maybe more for Colorcoats (which seem to take a long time before they stop smelling). If you don't wait long enough you might get cracking in the paint.

[wefalck]

I would not apply acrylic varnish over enamel paints. The old painters' rule is 'fat over lean', so enamel varnish over acrylics would be ok, but not the other way around. However, acrylic washes for weathering over (matt) enamels would be ok, as this does not form a uniform layer of paint. Whether the washes stick depends on the enamels and how rough/matt their surface is.

[EJFoeth]

I thought the general rule of thumb was lacquer < enamel < acrylics?

[wefalck]

Depends on the lacquer.

The general rule would be not to apply hydrophilic paints (i.e. paints based on the polar solvent water, such as acrylics or watercolours) over hydrphobic paints (i.e. oil- or non-polaric solvent-based paints). The inverse is possible, because the oil-based paints can key-in mechanically into the rough surface of the other paints. Conversely, in addition to be repelled due to Van-der-Waals forces, the water-based paints cannot key into the closed film of oil-based paints (it depends on their roughness also). It is a question also of the respective surface tension and the relative wet-ability. These are complex phyico-chemical surface processes. Alcohol-based acrylics may attack oil-based paints and therefore, could be able to get a foothold on them.

[Stephen Allen]

No problem applying an acrylic clear gloss over Colourcoats, provided you have let the enamel thoroughly cure. As an example I used AK Interactive Gauzy Intermediate Shine Enhancer (stupid long name I know but a good product) on my USS Fletcher to protect the Colourcoat base colours before weathering with oils. Similarly I have used Humbrol Acrylic gloss over Colourcoat painted armoured vehicles. In both cases airbrushed.

You really want an acrylic based barrier over your base coat if you are planning to use oils or enamels for weathering.

Cheers.

Steve