Sterling silver and gold fish knife, with photoetched fish decoration, and an ivory handle.
Materials and techniques
The ivory handles are sawn and filed into shape then polished. The silver parts are decorated using photo-etching drawn and photographed onto film. The metal sheet is coated with a liquid called photo-resist in a subdued light. After this is dry, the film is placed over the metal and this is exposed in ultra-violet light. The metal is then placed in a developer and the parts of resist not exposed to the light (ie. those parts covered by the black areas of the film) are washed away leaving a pattern of photo-resist, corresponding to the original design. After a further drying the metal is placed in a solution of ferric nitrate. This attacks metal not covered by the resist. In this way an etched design is worked into the metal and adter the required depth has been reached the resist can be removed. The silver sheet is then cut and formed into the correct shapes. They are then polished and slotted into the ivory where they are riveted into place. The gold decoration is applied last, by the riveting technique, since any heat would destroy the ivory.
Taken from 'Sutton/Treen' - Notes and Technical Information.