what is etching
etching. the cutting of a hard surface such as metal or glass by a corrosive chemical, usually an acid, in order to create a design. acid etching etching of dental enamel with an acid in order to roughen the surface, increase retention of resin sealant, and promote mechanical retention.he cutting of a hard surface such as metal or glass by a corrosive chemical, usually an acid, in order to create a design. acid etching etching of dental enamel with an acid in order to roughen the surface, increase retention of resin sealant, and promote mechanical retention.