Bar coating is a straightforward wet‑processing technique designed to apply a thin, uniform layer of liquid solution onto a substrate. The process works by positioning a coating bar — also known as a Mayer rod — on the substrate surface and drawing it across a reservoir of fluid; as the bar moves, it spreads the liquid into an even thin film or coating layer. Widely used in research, development and manufacturing, this method plays a key role in producing products such as automotive coatings, photovoltaic cells, and lithium‑ion batteries. Depending on the type of bar employed, the technique is also commonly referred to as drawdown coating, rod coating, wire‑bar coating, or Mayer rod coating.
Bar coating can be carried out manually, making it suitable for small‑scale work or laboratory trials, or performed using automated systems to achieve higher precision, repeatability and processing efficiency. In automated setups — such as the Ossila Bar Coater — an automatic film applicator moves the chosen bar (for example, a wire‑wound Mayer rod) across the substrate at a carefully controlled, consistent speed, ensuring consistent coating quality over the entire surface.