Yet another pointless varnish thread

[Jeremy]

So here’s one for the experts. Why is it, when I brush on Vallejo matt varnish, I get a kind of satin effect. Yet, when I airbrush that same varnish, I get a perfect matt finish? Is it because I thinned it? Is it because it is, as Freddy would say, under pressure?

[grizzlymc]

There is only one varnish - Testors dullkote, all else is apostasy.

[Jeremy]

That was exceedingly helpful. Thanks Grizz!

[Count Belisarius]

I brush on the Galleria matt. It's matt.

[goat major]

I’ll break tradition and attempt to answer the question

I suspect it’s the thinning. The satin effect is probably caused by the medium and by thinning it for the airbrush you’ve diluted the medium significantly. Also your airbrushed layer is much much thinner than you could ever brush on so there will be much less medium spread over your figure.

For no scientific reason I’ve tended to use daler rowney for brush on matt and Vallejo for spray-on (because the DR varnish requires white spirit to thin it and I don’t fancy spraying that)

[Jeremy]

Thanks GM!

[Zenbadger]

Daler Rowney & Windsor & Newton both go satin for me unless I varnish warm figures with warm varnish and then let them dry in the airing cupboard. I suspect temperature and humidity to be the key.

[Essex Boy]

Surface tension and light refraction. That's what you need to work on. Practice, practice, practice.

You're welcome.

[vexillia]

You're right it probably is pointless but I can add something that might help.

Basics Paint
[1] Paint is composed of pigments (finely ground solid particles) held in place by a medium. At a microscopic level the finish can range from smooth to rough and from very porous to just plain porous.
[3] When paint dries matt it is because the surface is rough such that it doesn't reflect light in a coherent manner.
[4] High pigment paints will tend to dry less shiny than low pigment paints as there's a greater chance of the pigment being at the surface.
[5] Some colours with low pigment levels (like red) are more prone to dry shiny (see 4). This also applies to excessively diluted paint unless diluted with matt medium.
[6] Cheap paints contain a lot of filler (usually talc). This is a good thing as far as the finish is concerned. The flat talc platelets produce both a rough surface (= matt finish) and lock together sealing the paint layer to penetration by solvents (see below).

Basics Varnish
[1] A matt finish relies on the matting agent (usually fine silica) being held on the surface of the top paint layer by the medium of the varnish.
[2] Porous paint surfaces will absorb the varnish preventing it forming a consistent surface layer and doing its job of matting the surface. In my experience, once the varnish has penetrated the paint it seems to change the paint layer making it even more permeable.
[3] On porous paint multiple coats will be required. This is to eventually seal the paint layer; then the final coat matts the finish.
[4] No varnish will penetrate paint that contains talc as the talc layer is impervious to both water and organic solvents.

Spray vs Brush On
[1] Sprays should (if done properly) dry the moment they reach the model. In these circumstances penetration of the surface is highly unlikely whatever the state of the surface.
[2] Over-spraying a varnish effectively reduces the difference between sprayed and brushed on varnish.

[vexillia]

Daler Rowney & Windsor & Newton both go satin for me unless I varnish warm figures with warm varnish and then let them dry in the airing cupboard. I suspect temperature and humidity to be the key.

Warming both the figures and the varnish will increase the rate at which the varnish evaporates and may minimise its ability to penetrate the top paint layer. Likewise for the drying regime.