How thin should I thin paint for airbrushing?

For base coating through an airbrush, aim for a consistency similar to skimmed milk. A ratio of 1 part paint to 0.5–1 part thinner is a good starting point. Acrylics such as Vallejo often need slightly more thinner than enamels like Humbrol or Tamiya. Always test spray on a piece of card before applying to your model.

What thinner should I use with each paint type?

Acrylics use dedicated acrylic thinner or clean water, though a purpose-made acrylic thinner gives better flow and retardation. Enamels use white spirit or dedicated enamel thinner. Lacquers require lacquer thinner — never use water. Oil paints are thinned with odourless white spirit or dedicated oil mediums such as Zestit.

Why does humidity affect thinning?

High humidity slows the evaporation of water-based acrylic thinners, extending working time. In very humid conditions you may need slightly less thinner because the paint stays workable longer. Low humidity speeds evaporation, which can cause acrylics to tip-dry in the airbrush needle, requiring a touch more thinner and a faster working pace.

Can I thin lacquer paints with acrylic thinner?

No. Lacquer and acrylic thinners are chemically incompatible. Mixing them will cause the paint to curdle and become unusable. Always use the correct manufacturer-recommended thinner for the paint type. Mr. Color paints use Mr. Color Levelling Thinner, and Tamiya lacquers use Tamiya Lacquer Thinner.

What ratio should I use for a panel line wash?

A panel line wash is very dilute — typically around 4:1 to 8:1 thinner to paint. The wash needs to be fluid enough to flow into recesses by capillary action but pigmented enough to leave visible colour. Apply over a cured gloss coat so the wash moves freely and can be wiped back cleanly.

ModelCalcs

Paint Thinning Calculator — Thinner Volume & Ratio for Model Paints

Calculate exactly how much thinner to add to your model paint for base coats, washes, glazes and dry brushing.

Paint Volume

Volume of paint you are thinning, in millilitres

Paint Type

The chemistry of your paint determines which thinner to use and base ratios

Target Consistency

The painting technique you are thinning for — each requires a different dilution level

Current Viscosity

How thick the paint is before thinning — straight from the pot or already partially thinned

How We Calculate This

This calculator uses base thinning ratios established by each consistency type and adjusts them for paint chemistry, current viscosity and environmental conditions.

The formula

Thinner volume = Paint volume × Base ratio × Paint-type modifier × Viscosity modifier × Evaporation factor × Humidity factor

Base ratio — the target thinning ratio for each consistency (e.g. 4:1 for washes, 0.5:1 for base coats)
Paint-type modifier — lacquers need less thinner than oils; acrylics sit in the middle
Viscosity modifier — thicker paint from the pot needs proportionally more thinner to reach the same target
Evaporation rate — faster-evaporating solvents require slightly more to compensate
Humidity factor — affects water-based paint open time and flow

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Always verify quantities before purchasing materials.