Thin your paint. For brush painting with water-based acrylics, water is all you need - no special product required. Aim for the consistency of milk. If your paint is dragging, streaking, or filling in detail, it is too thick. Add water, test on the palette, repeat until it flows cleanly. That is ninety-five percent of the answer. Note: water only works as a thinner for water-based acrylics while brush painting. We strongly discourage using water to thin acrylics for airbrushing, and water will not work at all for enamel or lacquer paints - both require their own dedicated thinners.

Multiple thin coats are always better than one thick one

The most common reason people do not thin their paint is the assumption that thick layers save time. They do not. A thick coat obscures detail, floods recesses, and dries unevenly - and then you spend time fixing it, or stripping the model entirely and starting over. That is the time cost of not thinning: not the thirty seconds it takes to add water, but the hours it takes to recover from a result you were never going to be happy with.

Two or three thin coats take longer per session and produce a cleaner result every time. The detail stays sharp, the colour builds evenly, and you are not fighting the paint. Thin coats are not the slow way. Stripping a model and restarting is the slow way.

Paint at pot consistency is formulated to survive shipping and storage, not to brush on cleanly. For brush application it is almost universally too thick: it drags across the surface, dries with the stroke direction visible, and sits on top of texture rather than settling into it. The assumption that paint comes ready to use straight from the pot is where most of the trouble starts.

Thinning to a milk-like consistency solves this because milk has the right balance of flow and body for a brush to carry and deposit paint cleanly. It moves off the brush with no resistance, settles flat as it dries, and does not pool at the edges of raised detail. That behaviour is what you are trying to replicate when you thin paint - not a specific ratio, not a rule, just that feel.

What you thin with matters too. For brush painting, water alone works but weakens the acrylic binder at higher dilutions and can cause beading and tide marks as it evaporates faster than the pigment. A small amount of acrylic medium mixed with water thins the paint while keeping the binder intact and improving flow. For most brush painting, medium plus water is more reliable than water alone. If you are airbrushing, do not use water to thin your acrylics - use a dedicated airbrush thinner instead. Water does not behave well through a nozzle and we strongly discourage it.

A basecoat at milk consistency will flow from the brush without resistance, settle flat while drying, and not pool at the edges of detail. If you pull the brush across a surface and can see the individual stroke direction in the dried result, the paint is still too thick. If the paint runs freely off the brush before you have touched the model, it has gone past milk toward water and lost too much body for reliable coverage.

The right number of coats is two or three, not one. A single thick coat trying to achieve full coverage will always be too thick. Two thinner coats that each approach coverage will produce a flatter, more even result with no filled detail. Building coverage across passes rather than forcing it in one is the fundamental shift that makes basecoating feel controllable.

How to test on the palette

Mix your paint on a wet palette and draw a thin line with the brush tip. The line should have clean, defined edges and be slightly translucent at thin areas. If the edges are ragged and the line is completely opaque even in thin areas, the paint is too thick. If the line bleeds or spreads beyond where the brush touched, it is too thin. A good basecoat mix sits cleanly without either failing.

Scale modelling note

For airbrushed basecoats on scale models, consistency is measured by how the paint atomises at your working pressure rather than by brush behaviour. The paint should mist finely onto the surface without spitting or running. Most dedicated airbrush paints are pre-thinned for typical hobby airbrush pressures; if you are thinning model colour or other brush paints for the airbrush, aim for a consistency closer to whole milk and adjust pressure downward rather than thinning too aggressively.

Purpose-made shade paints - Citadel Shades, Army Painter Quickshades, Pro Acryl Washes - are pre-formulated to the right consistency for wash work and can be used directly from the pot. When you thin your own washes from regular paint, the consistency needs to be substantially thinner than a basecoat: it should be watery enough to flow freely into crevices but retain enough pigment to leave a visible mark when dry.

The failure modes at each extreme are easy to recognise. Too thick: the wash sits on the surface rather than flowing, dries as a tide mark around the brush stroke, and does not shade recesses at all - it just tints everything. Too thin: the wash floods large areas evenly, loses all pooling behaviour, and produces a flat tint rather than targeted shadow. Either way, the shading effect is lost.

Application technique matters as much as consistency

A well-thinned wash applied to a surface that is too dry, too absorbent, or not sealed will still misbehave. A gloss varnish over the basecoat before washing gives shade paint a non-absorbent surface to flow across and produces cleaner, more controlled pooling. This is why experienced scale modellers almost universally seal before washing, even though the chemistry does not strictly require it for most paint combinations. The technique and the consistency work together.

A useful check: hold the brush tip just above the surface with the wash loaded, and let a single drop fall. If it immediately spreads into nearby recesses on its own, the consistency and surface are both right. If it sits as a dome or ball without spreading, the wash is too thick, the surface is too textured, or both.

Highlighting requires less thinning than most other stages, not more. The paint needs to be fluid enough to apply without dragging but opaque enough to sit on the raised edge as a clean line. Too much thinning and the highlight bleeds into surrounding areas, losing the crisp edge that makes a highlight read. Too little and the paint drags, pulls up the layer below, and leaves a rough edge.

The single most common highlight mistake is overloading the brush. The brush tip should carry just enough paint to deliver the stroke without pooling. Wipe the side of the brush on the palette before touching the model - the tip should still look loaded, but a light stroke on the palette should not leave a blob. That wicking step is doing most of the control work.

Edge highlights vs blended highlights

Edge highlights - the fine line along the sharpest point of an edge - generally use paint slightly thicker than a blended mid-highlight, because you need the opacity to show on a very small area. Blended highlights sit between the basecoat and the edge highlight in both position and consistency, and benefit from a slightly wetter mix that allows a small amount of wet-into-wet blending at the edges. These are different passes that ideally use slightly different mixes, not one consistency applied twice.

Glazing - applying an extremely thin translucent layer to subtly shift colour on finished work - uses the thinnest paint of any stage. The consistency is thinner than a wash and far thinner than a basecoat. When beginners first try glazing, they almost always use a mix that is too thick: it shows too dramatically, covers detail, and produces a stain rather than a subtle shift. A glaze that works is nearly invisible after one pass. The effect builds across multiple passes.

There is no reliable universal ratio. Pigment density varies significantly across paints: a highly saturated dark ink may need six parts medium to one part paint. A lighter, less dense layer colour may be workable at two to one. The palette test is the only guide: look at the pool on your palette in good light. If you can read the colour as a clearly distinct tint, it is too thick. If you can just barely identify it as a colour, you are close.

For more on glazing, including how glaze medium and Contrast medium behave differently and why the wrong one damages both techniques, see our full Three Glaze Myths article.

How to diagnose a consistency problem on a finished model

Most consistency problems leave a recognisable trace in the dried paint. If you know what to look for, you can identify what went wrong and correct it on the next model without guessing.

Visible brushstrokes in the dried basecoat

Paint was too thick. The brushstroke direction has dried into the layer because the paint could not self-level before drying. Fix: thin further and apply in shorter strokes, reloading more frequently.

Chalky or gritty surface texture

Paint was too thick, or dried too fast mid-stroke. The pigment has piled up unevenly rather than settling flat. This is especially common with white and yellow. Fix: thin more aggressively, use a damp brush to keep the working area wetter, and apply in lighter passes.

Tide marks around areas where wash was applied

The wash was too thick, or it ran onto an absorbent surface and dried before it could flow into recesses. The water evaporated first and left a pigment ring at the edge. Fix: seal with a gloss coat before washing, and ensure the wash is thin enough to flow freely.

Highlights that bled and lost their edge

Brush was overloaded, or the mix was too thin. The excess paint flooded beyond where the brush tip touched. Fix: wick more paint onto the palette before touching the model, and mix the highlight slightly thicker than feels natural.

Recesses that look flooded and muddy after washing

Wash was applied too liberally, or over a basecoat that was still slightly wet. The wash could not flow cleanly because the surface was not ready for it. Fix: let the basecoat cure fully before washing, apply the wash in smaller amounts, and wick excess off with a clean dry brush before it dries in unwanted areas.

All recommended products are stocked at Wheels & Wings Hobbies in Toronto and available online with Canada-wide shipping.