Baryta paper is the classic, top-quality photographic paper used in black-and-white photography. A white layer of barium-sulphate gelatine (called baryta) is applied to the paper ground, followed by a light-sensitive layer. A typical feature of classical photography is that this second, light-sensitive layer consists of silver halogen grains, usually silver bromide, suspended in gelatine. This light-sensitive layer is erroneously often called an emulsion; the correct chemical term is suspension since it dense particles are distributed through a viscous fluid. The silver halogenide in baryta paper is only sensitive to blue and violet light; therefore only red or yellowish green light can be used in the darkroom when photos are being developed on baryta paper. After exposure the photographic paper is developed, fixed, watered and dried. For glossy prints a dry press, also known as a baryta press, is used. When prints on baryta paper are carefully processed, the quality is excellent, with pure white, intense black and rich gradations of grey. Baryta paper is the most durable of all conventional photographic papers: prints on baryta paper can last more than a century. The developing process on baryta paper is so time-consuming and tricky that it is now only used for prints of particularly high quality.