Coating web with viscous liquid

Process comprises coating the web from below from a slit, the downstream wall of which defines a coating gap with the web at least twice the thickness of the required coating. To counteract web movement, there is an adjustable static pressure differential in the liquid between the inlet and outlet sides of the gap with the lower pressure at the inlet. The pressure differential is created by lowering the liquid level in a supply vessel relative to the level of the gap after coating has begun. Pref. liquid is fed to the supply vessel at the rate at which it is required to be applied, any difference in the rates automatically producing a change in level which eliminates the difference. Thus an even coating is applied independently of changes in, for example, liquid flow properties and web speed.