Stop-off Lacquer. A thick opaque inert fluid, which when applied to a surface and dries it prevents any action taking place to that surface. It is used in finishing medallic items as a protective covering on a portion of a medal while some other portion is plated, oxidized, or some other finishing operation. It stops both chemical and physical actions from occurring to the area so covered. Afterwards it is stripped off.

In acid etching a stop-off varnish is used in a similar way. It is far thinner consistency than stop-off lacquer and is painted or otherwise applied to the back and sides of metal plates where the etching is not to occur.

Stop-off lacquers and varnishes are available commercially. It is also known as a resist or resistant. In Great Britain the term is stopping-out or blocking-out.