A | B | C | D | E | F | G | H | I | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
A
Agemina or inlaid work
The pattern is routed out of the metal or precious stone using a burin. The spaces have to be undercut (usually with a trapezoidal cross-section) and have metal wires hammered into them to form a support until all the spaces are filled.Filing and final polishing highlight the pattern made by the colours of the various materials.
Alloying
Preparing a metal alloy by adding one or more metal or non-metal elements to a metal. Alloying is of enormous importance as it produces composites with characteristics suitable for any production and function needs.
B
Brazing
(see cleaning)
Burnishing
Protective treatment for metal surfaces with the creation of a fine, well-adhered layer of oxide or sulphur in a dark grey colour, also used for silver. This can be a chemical or heat treatment.
C
Chaser
(see repoussé)
Coating
Treatment of an article with special chemical components, which give a brown colouring. The raised parts are then cleaned, highlighting the relief effect.
Coining
Pressing of metal articles, generally coins and medals, mainly in round shapes.
Commesso or mosaic-style with semi-precious stones
This is an inlay composition where semi-precious stones in a wide range of colours are used together, making the most of the different colours to create chiaroscuro chromatic effects. This technique is used for decorating altar frontals and table tops. Widely used in gold jewellery since the Renaissance. The Medici promoted this technique with the founding of the Opificio delle Pietre Dure for the working of semi-precious stones.
D
Deoxidation
Heat treatment carried out on a metal in its solid state in a reducing gassy atmosphere. It is carried out in muffle or bell kilns at a temperature that reduces oxides.
E
Electroforming
A manufacturing technique for producing metal pieces or printed circuits from negatives or matrixes. It is used for reproducing an object (medal, small statue, etc...) through an electrochemical process. Matrixes for reproduction can be made from metal or other substances. When using non-metals, the matrix is generally made out of a gelatinous material and fine layers of metallic powders or vapours are used to make its surface conductive and activate the galvanic deposits of the coating material. In some cases the matrixes are melted to give a hollow lightweight article.
Enamels
These are silicate (glass) composites ground into powder and coloured with the addition of metallic oxides. This powder in suspension in water, is applied to the cavities or the surfaces to be decorated and then melted in special kilns. There are various enamelling techniques and methods, summarised briefly as follows:
Champlevé: the application of enamels to cells (troughs) engraved (cut out) of the surface.
Cloisonné: the enamel powders are inserted into cells outlined by fine metal wires (cloisins) welded to the body of the object.
Basse-taille: this uses an engraved or chased low-relief pattern on the metal as a base, which is then covered with transparent enamel. The varying depths of the low-relief and the cuts create surprising chiaroscuro effects.
Engraving
Various depths of grooves make a pattern formed by sharp tools called burins, which remove and dig into the metal of a surface that may be flat or shaped.
It is different from chasing, with which it is often confused, as the latter involves moving the metal and not removing it.
F
Filigree
This is the composition of the finest flattened wires, either smooth or rope-like, wound around in spirals, circles and wavy lines. It can also be in a perforated design when the element s are welded together and are not supported on a base sheet.
Fusion
The main fusion techniques used in gold jewellery manufacture are:
clamp method: pressure is used to make a negative of a model for reproduction, on special sand, normally called “Foundry sand”, held between two metallic clamps.
The model is removed by opening the clamps, sprues are cut into the sand and the two clamps are closed again to allow drying and casting with molten metal.
This technique is generally used for medals and small tags because undercuts cannot be obtained in this way.
Cuttlefish method: two cuttlefish bones are rubbed together to smooth them and a previously prepared model is then pressed between them by hand to give a negative impression. The model is removed, sprues are cut out, the two bones are put back together and tied together with wire and then filled with the molten metal.
G
Gilding
A technological operation used for coating an article in any kind of substance with a very fine layer of gold.Gilding was known to the Egyptians Egypt and to the Greeks and Romans, who used it to embellish furniture, arms, statues, vases, etc. It was widely used in the Middle Ages on paintings for the haloes of saints and for bases of icons, illuminated manuscripts, tablets (so-called gold backgrounds) frescos and friezes.
Gold was either put onto the backgrounds, previously prepared with Armenian bole or with mordant in very fine sheets, or was ground into a very fine powder, diluted and then painted on. Before electrolyte techniques were perfected, gilding was exclusively carried out using fire or plating.
Glyptics
This is the technique of cutting and engraving semi-precious stones and shells for cameos.The stones (or shells) can be of the layered type (like agate or chalcedony) thus permitting the creation of bas relief items in various colours or single colours, called cameos.
The stones can be engraved with indented patterns to make seals.
Gold leaf
Extremely thin, almost impalpable sheet of gold, used for gilding or decoration.Such fine gold leaf is obtained by beating piles of sheets separated by special papers, held tight between two tanned donkey skin sleeves.
The art of gold-beating was also known in ancient times when the profession had its own craft corporations.
Granulation
An ancient gold jewellery technique whereby gold grains placed on a sheet of gold and welded are used to make ornamental patterns. The oldest examples of granulation date back to a number of gold workshops of the so-called “Treasure of Priamus" (circa 2350-2100 B.C.). Granulation jewels have been found in Egypt (the Cairo Museum), Crete (Gold Bee Pendant), Mycenae (Gold Frog Pendant) and are also documented in Greek art, especially in the Geometric period.
The most sophisticated examples however belong to Etruscan gold jewellery which reached a very high level of perfection.Some craftsmen and artists have attempted to reproduce granulation on pieces inspired by these ancient eras, including the Roman Castellani goldsmiths, who achieved good results.
Guilloche
A mechanical engraving method on flat and domed surfaces. The engraving tool remains immobile and copies a set design (rice grain, waves, etc...) while the article being engraved is moved.
The French goldsmith Fabergé used this technique widely around 1883 when he worked for the Tsars.
H
Hammer and lathe modelling
When the metal sheets are hammered and hammer-flattened on special anvils to make generally bowl-shaped objects used as holy ware and vases.
Metal-sheet discs for plates and trays are lathe-turned and modelled on special wooden shapes with burnishers (large-headed tools) pushed by hand, using the fixed pins of the turning lathe for leverage.
Heat treatments
A group of operations carried out on materials in order to change their physical state and obtain particular properties and characteristics.
Hollow-section production
Hollow-section in sheet or bars used to make tubes that vary in diameter and offer considerable rigidity to bending and resistance to twisting without excess weight.
Hollow-section is also used incorrectly to mean the formation of solid bodies through the application of a flat or shaped base to previously moulded hollow items that, with the prerogative of seeming solid, add the characteristics of robustness and lightness in proportion to apparent volume.
K
Knurling
Continuous pressing operation of metal ribbons used mainly for the decoration of heavy silverware. Rolling mills are used, into which are inserted shaped cylinders that act as matrixes for pressing..
M
Mounting
he word used to refer to setting stones into jewellery, below is a list of the most important methods:
open-back: when the stone is transparent and prongs are used that allow the light to pass through the sides and from underneath, to enhance the brilliance of the stone.
closed-back: when the stones are not transparent and the prongs may have a backing and side edging without allow the light through.
Claw: when the stones are held in place by a crown of tapered prongs whose ends curve over.
Bezel: when the stones are held in place by a metal border, folded over at the top by hammering with chasing tools.
Pavé: setting used for facetted stones placed one next to another; it takes the name from paving.
Riviere: when the stones are set alongside each other in a continuous line, their individual settings may even be connected by joining links.
N
Niello
This is a black-coloured mixture obtained by melting together silver, copper, tin, lead and sulphur.
It is applied to engravings like enamel and melted by a heat source so that it fills the grooves. Then it is filed and polished to eliminate an excess material and to show up all the beauty of the pattern.
P
Plating
An operation that consists of covering the surface of articles, mainly metal, with a fine layer of another solid material. Unlike gilding or silvering (galvanic treatments), plating is carried out by mechanical fixing of two different metals or alloys. This is necessary when the layer used for covering must have a high chemical-mechanical resistance or in the construction of gold and silver articles that must meet weight requirements. In the latter case, plating using precious alloy sheets is carried out on non-noble metals that act as a support and make for ease of working and are chemically removed once the article is finished.
Polishing (or cleaning)
A process used to give a certain degree of surface finish to the final article. Cleaning may be mechanical or electrolytic. Mechanical cleaning involves placing the article against an abrasive on moving brushes. Electrolytic cleaning is an operation that polishes a metal surface made the anode of a cell, whose electrolytic bath changes according to the metal being treated.
R
Removal
Term used in gold jewellery production for the chemical or mechanical removal of the non-precious material used as a core for the construction of articles that must meet certain weight and volume requisites. This operation is the natural complement for articles made in two-metal materials through plating.
Repoussé and Chasing
The decoration or the pattern are worked in relief from the back of a sheet of metal and then embossed with wide punches hit with a hammer. To allow the metal to deform, the lamina is applied to a piece of hot pitch.Once the desired shape has been achieved, the sheet is removed from the pitch and cleaned. The cavities are once again filled with pitch and the pattern is finished from above, with the outlines and details defined using chasing punches.
It must be noted that these do not remove the metal, they simply move it..
S
Satin-finishing (or silk-finishing)
This operation leaves the external surface of a gold or silver article matt or silky looking and is carried out with a burin or very fine grinding wheel.
Stamping
A mechanical operation for processing sheet or solid metal in one or more stages, without producing waste, in order to obtain an object that has its own shape, either flat, solid or hollow.
Tools called dies are used in special machines that apply static or dynamic pressure to the pieces.
T
Trimming
Mechanical operation that defines the outlines and cleans up the item, removing processing waste.
W
Welding
Technological process that joins two or more metal pieces using heat, with or without the use of metal material.The most widespread types of welding are: fusion, pressure, brazewelding and brazing.