How to Thin Acrylic Paint for Miniatures

To thin acrylic paint for miniatures, mix it with a thinner or medium made for acrylics, a little at a time, until it flows off the brush in a smooth, slightly see-through coat. Most hobby paint is thicker than the best painting consistency, and a thinner such as Vallejo Thinner Medium or AK Acrylic Thinner brings it down without turning it weak and watery.

Why should you thin acrylic paint for miniatures?

Paint straight from the pot is made to be stable on a shelf, not to sit gracefully on a 28mm face. Thick paint hides sculpted detail, leaves brush marks and clumps in recesses. Thinned paint settles into the surface, and two thin coats cover better than one heavy one. It is the single habit that most changes how a painted army looks up close.

Thinning also sets up everything else you do with a brush: smooth base coats, shading, glazing and layering all depend on paint that flows where you put it and stops where you stop.

Thinner, water or medium: which should you use?

Water is the first thing most painters reach for, and a few drops are fine. The trouble is that paint is a pigment held in a binder, and water dilutes both. Vallejo formulates its thinner to dilute color without loss of adhesion, resistance or consistency, so the thinned paint still grips the surface and holds up as it would from the bottle. In its own words, that is the point of using a thinner instead of plain water.

Here is how the main types differ:

• Thinner. Brings the paint to a working consistency. Vallejo Thinner Medium (70.524) increases the flow and transparency of colors; AK Acrylic Thinner is a water based thinner, non-toxic and odorless, for brush or airbrush, and AK says it is compatible with other brands.
• Glaze medium. A colorless medium that improves fluidity, increases transparency and slows drying. Vallejo recommends its Glaze Medium (70.596) for shadows, shadings, glazes and working with pigments.
• Retarder. Slows drying. AK Drying Retarder gives more time to thin paint into glazes and build smooth, translucent layers, or to blend in a controlled way.
• Flow improver. Helps paint move, mostly an airbrush job. Vallejo's Airbrush Flow Improver improves the flow of the paint and delays drying, at three drops to every ten drops of paint.

How much thinner do you add?

Start with a little less than you think you need. Vallejo gives hard limits for its Airbrush Thinner: for airbrush colors, a maximum of 25% thinner, and for colors applied by brush, a maximum of 50%. Stay inside those numbers and the paint keeps what it came with.

1. Put a small blob of paint on your palette. Do not thin the whole pot.
2. Add thinner a drop at a time. Count the drops so you can repeat the mix next session.
3. Mix, then test. Paint a stroke on the back of your hand or a spare base. It should flow without pooling and leave the color visible in one pass or two.
4. Adjust. Too see-through, add paint. Too thick and dragging, add a drop more thinner.

How do you thin Speedpaint?

Speedpaint is made to shade and color in a single coat, which is why its thinning medium is a separate product. The Army Painter Speedpaint Medium is a resin medium that thins Speedpaints to the consistency a job calls for: each drop added on the palette makes the color more transparent, so less pigment reaches the model. The Army Painter names glazing and tinting as the techniques it makes easy. It comes in an 18ml spill-free dropper bottle, and in a 100ml dropper bottle for painters who use it often. Both have mixing balls pre-loaded in the bottle.

What about thinning paint for an airbrush?

An airbrush asks for thinner paint than a brush does, and the usual limit is the nozzle. Vallejo Airbrush Thinner is sold in a large 200ml bottle for painters who spray regularly, and AK's 3G Thinner is made for maximum airbrush performance and to prevent paint jamming or clogging. If paint is drying at the tip, a flow improver or retarder is the tool for that job rather than more thinner.

Does a wet palette change how you thin?

It does, and for the better. A wet palette keeps a thinned mix at the same consistency from the first brushstroke to the last, so you stop re-thinning a mix that has started to skin over. If you have not set one up, our guide to what a wet palette is and which to buy covers it.

What should you get first?

One thinner for everyday brush work, and a medium for the paint line you use most. If you paint with Speedpaint, the Army Painter medium is the natural pair. If you are new, our first miniature paint kit guide lists what to put on the bench, and how to prime miniatures covers the step before you start painting. Everything for the bench lives in our paint and hobby supplies.