paint wrinkling

[piggypod1]

Hi, i've spray coated humbrol acrylic matt varnish over brush painted xtracolour enamels and on several occasions the varnish has wrinkled the paint and has in effect ruined many hours of paintwork, does anyone know the cause as i have now reverted to brush painting humbrol enamel vernish and putting up with the resulting brush marks, any suggestions, thanks Phil

[DAL-T]

I made the same mistake long ago on a lovingly decorated Mustang (Ford, not North American). The trouble is acrylic varnish forms an impermeable layer which prevents the solvents in the enamel continuing to evaporate. It has to be either acrylic on acrylic or enamel on enamel - brush or spray shouldn't matter, and with a wide, flat brush and properly thinned varnish there shouldn't be any marks left from the hairy stick. Everyone has their favourites, of course, but personally I avoid Humbrol varnish like the plague and use either Ronseal or Xtracolor. For matt, Xtracolor FF is, in my view, unequalled, particularly at returning an even finish if some areas are already matt and others have been glossed for decalling.

[piggypod1]

Thanks for the advice, 50 years old and i never realised paint continued to give off fumes and continued to dry under varnish, are you referring to Xtracolour flat in 250ml bottles and do you spray or brush, thanks phil

[DAL-T]

The bottles I have are 75ml, although Hannants also used to do tins the same size as their normal paint (14ml?), which now seem to be discontinued - I think they were just 'F' (or 'S' for satin) and 'FF/SS' actually denotes the larger size. For final coat varnish, and glossing for decals when needed, I both spray and brush, depending on the model (anything up to 1/72 Spitfire/Bf 109 size gets brushed, larger gets sprayed). I thin with Xtracolor thinners, which are quite high-flash, if spraying, or artist-quality white spirit if brushing (for clean-up I use general purpose w/s, sourced in volume from B&Q in the UK or any local supermarket here in France, at a fraction of the price).

I'm no paint technician, but it's my understanding enamel still gives off significant solvent fumes long after seeming to have dried and hardened - I've been told that's at least as long as it takes oil paint to dry, and I know I always under-estimate how long that is when I use oils for figure painting. If you wait long enough it might just be possible to get away with overcoating with acrylic, but I think the fact that Humbrol include enamel varnishes in their 'acrylic' range (with adverts saying 'because enamel paint needs special varnish') suggests it's just not worth the risk. Cheers, David.