Weathering Wash Mix Calculator — Paint-to-Thinner Ratio & Volume

Enamel washes are widely regarded as the most controllable for panel line work because they remain workable for several hours and excess can be removed cleanly with white spirit without disturbing the underlying acrylic base coat (provided the base is fully cured under a gloss clear coat). Oil washes offer even longer working times. Acrylic washes are safer to use (no solvents) but dry quickly and are harder to remove cleanly.

A gloss clear coat creates a smooth, non-porous surface that allows the wash to flow freely by capillary action into recesses rather than being absorbed by a matt base coat. Without a gloss coat the wash will stain the surface unevenly and be almost impossible to remove cleanly. Apply a gloss coat and allow it to cure fully — at least 24 hours for solvent-based clears — before applying washes.

Larger scales have physically wider and deeper panel lines at the model surface. A 1:35 AFV has panel lines roughly twice as wide as the equivalent 1:72 aircraft feature. Wider lines hold more wash by volume, so you need proportionally more wash on larger scale models to fill the recesses sufficiently.

There is no single correct ratio — it depends on the effect. As starting points: a panel-line or pin wash that needs to flow into recesses and stay put is usually around 1 part paint to 3–5 parts thinner; a general all-over wash is roughly 1:4 (about 20% paint); and a very thin filter-style wash that subtly tints the surface can be 1:10 to 1:20 (5–10% paint). This calculator defaults to enamel 1:12, oil 1:8 and acrylic 1:6, but the Dilution Ratio Override lets you dial in any value from about 1:3 to 1:30. Mix thinner than you think you need and build up — you can always add more paint, but an over-pigmented wash stains and is hard to remove.

For enamel washes, dampen a cotton bud or flat brush with white spirit or odourless enamel thinner and gently stroke along the surface away from the panel lines. Never scrub. For oil washes, use the same technique while the paint is still pliable. For acrylic washes, work quickly and use a clean damp (not wet) brush. Always work in the direction of panel lines to leave residue where it reads most naturally.