There is clearly some reaction between the paint surface and the varnish. I don’t know what it is but it is preventing the matting agent in the varnish migrating to the surface and disrupting the surface for a matt finish.
However, all is not lost as this week I stumbled across a really simple solution.
Whilst surfing the web I read an article on the Kings Miniatures blog on converting artists acrylics into miniature paints and I noticed this comment:
“Next add a small amount of industrial talc. Adding talc gives a solidity and glow to the paint you may find familiar. Back in the 1990s, a white dwarf article mentioned that talc is used in citadel paints, so having talc on your models was not going to effect the paint job much- this clued me into trying it out, and it makes a big difference to some mixes.”So I wondered if the talc would also act as a matting agent. In the past I have used fumed silica to improve the matting properties of Humbrol Matt Cote. The fumed silica was provided by a neighbour who worked in a paint laboratory but as he’s now retired I only have access to standard cosmetic talc.
I bought a life times supply of colour and perfume free talc from the local Chemists and experimented with adding small amounts to samples of the problematic paints. I started adding very small amounts but quickly realised that the paint will take quite a lot of talc before refusing to flow. It’s easy to do on a palette so experiment for yourself to get the quantities right.
I’m pleased to report that it works really well producing a very flat finish. There was little change in colour and any change is solely due to the lack of any surface sheen.
I’m going to continue adding talc to paints on my palette for while. I have added talc to some dropper bottles but I’m certain I’ve not yet added enough. I think I’ll get used to the technique first before attempting to fix a whole bottle.
Follow up article after some months experience.