Tamiya 81040 Acrylic Paint Thinner X-20A 250ml Bottle Review (2026)

What this thinner is made for

X-20A is Tamiya's acrylic and polycarbonate thinner, built specifically to dilute Tamiya Color acrylic paints to the right consistency for airbrushing, and it also doubles as a cleaner for brushes and airbrush parts after use. Because it is formulated around Tamiya's own acrylic paint chemistry, it is the manufacturer's recommended pairing rather than a generic thinner meant to work equally well across every acrylic paint brand on the market, and builders using a different acrylic line are generally better served by that brand's own matched thinner. Tamiya sells the same formula in smaller bottles too, so this 250ml size is simply the higher volume option within that same product line.

Bottle size and value for regular airbrushing

At 250ml, this bottle is considerably larger than Tamiya's smaller thinner bottles meant for occasional brush painting, making it a more economical choice for anyone airbrushing regularly, since thinner gets used up quickly once paint is being reduced for spray consistency on every color change. Buying the larger bottle also means fewer reorders and less risk of running out mid session compared to keeping only small bottles on hand, which matters when a painting session depends on having enough thinner to keep paint flowing smoothly through an airbrush. A builder working through several kits a year will likely find the larger bottle pays for itself compared to repeatedly buying smaller ones.

Flow, drying time and workability

Thinning Tamiya acrylics with their matched X-20A formula is described as giving smoother flow through an airbrush and slower drying than the paint alone, which gives more working time to blend colors or fix a spot before the paint sets. Slower drying is a meaningful practical benefit during airbrush work specifically, since paint that dries too fast in the air between the nozzle and the model surface can lead to a rough, stippled finish rather than a smooth coat, and a properly thinned mix reduces that risk. Getting the ratio right takes some testing per color, since coverage and pigment density vary across Tamiya's acrylic range.

Cleanup duties

Beyond thinning paint for application, X-20A also serves as a cleaner for brushes and airbrush components after a painting session, dissolving residual acrylic paint that would otherwise dry and clog fine airbrush passages or stiffen brush bristles. Keeping a dedicated bottle for cleanup separate from the thinner used in active paint mixes is a common practice, since paint tinted cleanup thinner is best kept away from fresh color mixes. This dual role as both a mixing thinner and a cleaner is part of why a larger bottle offers good value for anyone doing much airbrush work.

Fit within a Tamiya focused paint setup

For a builder working primarily or entirely in Tamiya Color acrylics, this thinner is the straightforward, manufacturer recommended choice that avoids the guesswork of testing a third party or cross brand thinner against Tamiya's specific paint formula. Builders mixing paint brands on the same shelf, such as pairing Tamiya with Mr. Hobby or Vallejo, should expect to keep each brand's matched thinner on hand separately rather than relying on one bottle to serve every paint line evenly, since acrylic formulas differ enough between manufacturers that results can vary. Sticking with the matched thinner is the simplest way to keep spray results consistent from one session to the next.

Frequently asked questions