Paper-like nonwoven fabrics made using short fibers suspended in a liquid are referred to as "wetlaid". To distinguish wetlaid nonwovens from wetlaid paper, a material is defined by EDANA as a nonwoven if "more than 50% by mass of its fiberous content is made up of fibers (excluding chemically-digested vegtable fibers) with a length to diameter ratio greater than 300, or more than 30% fiber content for materials with a density less than 0.40% g/cm3". This definition excludes most wetlaid glass fiber fabrics that others would class as nonwovens.
The wetlaid process was initially developed in the 1930s by Dexter as an attempt to reproduce special papers made in Japan using long fibers. Dexter's solution was to lower the the fiber to water ratio and incline the angle of the forming wire - the inclined wire system. In general, the fibers are suspended in a diluted slurry and deposited on a moving screen that allows water to pass through the screen and fibers to collect on the screen. The machine direction (MD:CD) ratio of the fabric being formed can also be influenced by the velocity of the water and the angle of the wire system.
Compared to the dry web-making processes (carding, aerodynamic and spun web methods) the distinctive features of the wet method are its high productivity and wide range of application. One of the key advantages of the wetlaid system is the ability to process many types of fibers including leather, Kevlar, glass, and stainless steel. However, sythetic fibers for use in wet-laid nonwovens are 20% to 50% more expensive than the same fiber in the form of textile staple, because the market is small relative to that for textile fibers, and special handling and cutting are required. Specialty fibers such as low-melting bicomponent fibers are even more expensive, and their total production is too small to allow economics of scale to be fully realized. Only a small number of companies use a wetlaid process due to the high cost of equipment and substantial volumes of water needed.