Coating - What does coating mean?
This entry has two definitions:
In labelling, coating refers both to a substance and the process of applying that substance to label materials. A coating is a (usually liquid) material that is used to create a film that covers the surface (or surfaces) of one or more of the layers within a label construction. Coatings enhance the appearance and finish of a surface, add a protective layer over a surface, improves the printability of a surface, or promote adhesion between adjacent or subsequent layers and substances.
The coating is usually applied in a liquid state that turns into a solid film through oxidation (chemical reaction with oxygen), evaporation (carrier substance turns into a gas leaving a solid film behind), or polymerisation (chemical reaction caused by a catalyst). Common types of coating substances include emulsions, lacquers, and varnishes. Coatings can be applied on press during the manufacturing or converting processes, or as a separate finishing operation before or after a label has been printed, and are either applied over the entire surface of a material (over coat) or to sections of the surface only (spot coat).
In paper manufacturing, coating is one of the final steps in the manufacturing process and is used to determine key characteristics of the final paper product, including opacity, surface smoothness, finish, colour, whiteness, brightness, and printability (including ink receptivity). A substance (or coat) is applied to the entire surface of the paper while it is on the paper machine or on a separate machine entirely.
A coat is a mixture of pigments and binders (sometimes referred to as adhesives), although additional chemicals may also be used to control the properties of the finished material. The coat fills the gaps between fibres in the paper, which improves its surface smoothness, and the pigments contained in the coat enhance its finish as required. For example, refined clay creates a glossy finish, titanium dioxide improves brightness and opacity, and calcium carbonate increases the ink absorbency of paper. Paper that has undergone coating is referred to as coated paper, while paper that has not is known as uncoated paper.Go Back to Glossary