Thinner

Thinner is a volatile solvent added to paints, varnishes, and coatings to reduce viscosity and improve application. By lowering the solid content, it helps coatings flow more easily, level out, and wet the substrate. Thinners are used with solvent-based systems such as enamels, varnishes, and oil-based paints. For water-based systems, water itself often serves as the thinner, though some products use specially formulated additives.

Common solvent-based thinners include mineral spirits (white spirit), naphtha, turpentine, xylene, toluene, acetone, and ethyl acetate. These substances vary in evaporation rate, polarity, and compatibility with binder resins. The choice of thinner affects drying time, gloss, leveling, and the properties of the final film. Always use the thinner recommended by the coating’s manufacturer and mix in appropriate ratios.

Safety and environmental considerations are important. Thinners are typically highly flammable and emit vapors that can be harmful if inhaled or absorbed through the skin. Use in well-ventilated areas, keep away from ignition sources, and store containers tightly closed. Dispose of waste and rags according to local regulations to prevent fire and environmental harm. Many regions regulate volatile organic compound (VOC) content in thinners and related products.

Tips for use include testing a small amount on a scrap surface, adding thinner gradually to reach the desired viscosity, and avoiding over-thinning beyond manufacturer guidance. In some industries, thinners are labeled as reducers or diluents and are formulated to match specific paint systems.