The function of paint thinner and the typical usage ratio

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The functions of paint thinners and the typical usage ratios I. Functions of thinners ① Reduce the viscosity of paint, making it thinner and easier to apply by brushing/spraying; this reduces the likelihood of brush marks and uneven application. ②To adjust the drying speed, use a slow-drying anti-dry brush or pinholes in summer ； Use a fast-drying, anti-whitening type in winter; it doesn’t leave residue. ③After using the cleaning tool’s spray gun or paint brush, clean it immediately with a solvent to prevent curing from blocking the gun. ④Improving film formation quality: if it’s too thick, it will cause orange peel effect and wrinkling ； If it’s too thin, it will run and have poor coverage. II. Common paint thinning ratios (weight/volume; for beginners)
1. Alkyd paints (ordinary anti-rust paints, mixed paints, enamel paints)
Ratio: Thinner:paint = 5%–15%. That is, 1 L of paint requires 50–150 ml of thinner. Use a thicker mixture for brushing (5%–10%) and a thinner one for spraying (10%–15%).
2. Epoxy paints (H06-1 epoxy zinc-rich primer, epoxy ferrochrome intermediate coat, epoxy topcoat)
Ratio: 5%–10%. Note: An epoxy-specific thinner must be used; acetone cannot be used. Using too much thinner will result in sagging, loss of luster, slow curing, and reduced adhesion.
3. Acrylic and polyurethane paints
Ratio: 5%–12%. Use slightly more thinner for spraying and slightly less for brushing; it’s better to use less rather than too much.

III. General judgment methods (accurate without a scale)
For brushing: The paint should spread smoothly without leaving obvious brush marks.
For spraying: The paint should emerge in a misty form, without stringing or clogging the sprayer.
Principle: Add thinner in small amounts multiple times instead of adding a large amount at once.

IV. Important precautions
Thinner types specific to different paint systems must not be mixed up (use epoxy thinner for epoxy paints, and high-temperature paint thinner for high-temperature paints). Use less thinner in low-temperature and high-humidity conditions, as this can prevent proper drying and cause whitening. Thinner is flammable; ensure good ventilation during application, and avoid open flames