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Introduction
This page summarises my experience of using talc to treat hobby paints such that, when varnished, they dry matt. I first started to use it in 2011 and there's still a small jar of talc on my desk to this day.
Background
I ran into a persisitent problem varnishing my figures. Certain acrylic paints, mainly Vallejo reds and browns, dried satin or slightly gloss and no varnish, or combination of finishes, would produce a matt finish.
There was clearly some reaction between the paint surface and the varnish. At first, I did’t know what it was, but whatever it was it was preventing the matting agent in the varnish migrating to the surface and disrupting the surface for a matt finish.
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.”
I wondered if the talc would also act as a matting agent and therefore improve the finish on varnishing. 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 had access to standard cosmetic talc.
Initial experiments
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 just 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 and I soon learnt how much to add.
I found it worked 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. More importantly, varnishing the flattened paint produced a flat finish too.
Established technique
After six months or so of experimenting I settled on this approach:
- I transferred a small amount of talc to a clean, old paint bottle with a screw top. This is so much more convenient than opening a large bottle every time.
- I use a wet brush to pick up some talc and mix it with the paint. I’ve also found that it’s not necessary to clean the brush beforehand. The talc sticks to the paint and the talc left in the well stays clean. This is a very useful property
- I’ve also found that the easiest way to matt a portion of paint is to add two or three “dipped brushfuls” of talc. I stop adding talc just as the paint starts to look like a paste. I then thin the mix with just enough water to make the paint flow again.
This above has worked with paints from Vallejo, Rackham, Miniature Paints, Coat d’Arms and various cheap craft paints. I’m so used to doing this, that I curse myself when I forget (and end up with a shiny layer of paint).
I’ve treated whole bottles of paints too, but I’ve been careful not to add too much talc. I tend to add just enough talc so that I only have to add a final touch extra when the paint is on the palette.
I’ve also erred on the side of caution and added some matt medium after the talc just to maintain the fluidity of the paint in the bottle. By the way the matt medium does not flatten the paint on it’s own: I tried that first!
Many years later
After over a decade's experience:
- I still routinely add a touch of talc to many of my paints. I soon learnt which paints need talc and which did't.
- I really like the way it removes any insecurities about varnishing.
- The flat finish also helps to see any highlights during painting (less shine).
- I'm also pleased to say that I've not seen any changes in paint adhesion at all, which is a big plus.
- I seldom now add to talc to a whole bottle, because adequate mixing is a problem. It's much better to add small amounts of talc by brush to paint on a palette.
Why does it work?
Whilst adding talc solved all my varnishing problems I remained puzzled why I had a problem to begin with.
It didn't make sense that certain "un-talced" colours gave a satin finish after varnishing even if the paint was perfectly flat before varnishing and that further coats of varnish had no effect whatsoever. It wasn't just frustrating, it didn't make sense
In 2014 I did a bit of research online and found that the addition of talc doesn't just produce a flat paint surface. As the paint dries the talc particles, which are flat platelets, align with one another creating a barrier that cannot be penetrated by my preferred spirit based varnish. To my surprise I found it was this "sealant" effect that solves the varnish problem not the visible matting effect.
With problem paints, like "un-talced" reds and red/browns, the varnish penetrates the paint layer and the matting effect of the varnish is lost. As varnishing does not seal the paint, further coats of varnish have no effect either. The addition of talc ensures the paint is sealed enough so the varnish forms a discrete surface layer during drying and works as designed.
In 2025 I used an AI chatbot to re-investigate this. The resultant discussion explained that the talc platelets only provide a partial seal and they aren't a replacement for a specific isolation coat. Even so, in my hands it's more than enough "sealant" to solve this common hobby issue.
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