Glossary of Terms

  • Air Cool
    • When one leaves the piece of metal to cool by itself.

  • Annealing
    • Heat treatment process to soften material that has hardened during rolling or drawing processes.

  • Arc Welding
    • A type of welding that uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. They can use either direct (DC) or alternating (AC) current, and consumable or non-consumable electrodes. The actual base metal does melt and no solder is involved or needed.

  • Base Metal
    • Term for non precious metals e.g. aluminum, brass, copper, steel, and pewter

  • Brazing
    • Brazing is a metal-joining process in which two or more metal items are tightly joined together by melting and flowing a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Brazing is done at a higher temperature to soldering and has a stronger join. The base metal doesn’t melt just the brazing rod.

  • Buff
    • Same as polish.

  • Burnisher
    • A hand tool used to polish metal.

  • Burn Out
    • In casting when the wax is burnt out.

  • Carat – Gold
    • A term used to denote the fine gold content of precious metal alloys. The designation for fine gold is 24ct, therefore 9ct is 9/24 or 37.5% pure. Also a unit of weight used for precious stones – a carat is one fith of a gram

  • Ductile
    • Used to describe a metal that is pliable, allowing it to be stetched and thinned.

  • Electroplating
    • The process of covering a metal with a thin film of another metal. The metal is set in a chemical solution, through which an electric current flows to coat it with the other metal.

  • Enamelling
    • Colour technique applied to jewellery.

  • Fire / Fire Free
    • Fire is the term used to describe the red staining associated with the formation of copper oxide on or near the surface of material. Fire-free refers to material produced under controlled conditions to prevent this happening i.e. annealed under a protective atmosphere. Fire stain can also be minimised in subsequent heating and soldering operations by using a protective covering, Cookson supply a product known as Argotect for this purpose.

  • Flux
    • Used as part of the soldering process, flux is a chemical applied to areas to be soldered. Prevents oxides forming and allows the solder to run.

  • Hardness
    • The resistance of a metal or alloy to the penetration of another substance, or to abrasion i.e. wearing or machining. The hardness (or temper) of a metal determines its ability to be worked. Hardness is measured by a scale known as VPN (Vickers Pyramid Number). Certain manufacturing processes in the jewellery industry require material at a given hardness e.g., pins for earwires and material may be ordered as hard, half hard, quarter hard or by a specific VPN number

  • Malleable
    • A term used to describe a material than can be formed without splitting or breaking.

  • Oxidation
    • Metal blackened by a reaction with oxygen. The appearance is achieved by a chemical process.

  • Pickling
    • A mild acid bath treatment to dissolve the surface oxidation of metal which occurs when metal is heat treated in open air rather than atmosphere controlled conditions. Essentially a cleaning process.

  • Porosity
    • A defect which affects the surface finish of any product which has been manufactured via a casting process. It is caused by gas entrapment present in the product and generally only becomes apparent during the final finishing (polishing) process. It consists of a series of pinholes which become evident as the top surface of metal is polished away.

  • Quench
    • The act of placing hot metals into water.

  • Rhodium
    • A white, metallic element used for plating items white.

  • Soldering
    • A low-temperature analogue to brazing. soldering takes place with fillers (also known as solders) that melt at below 450°C. The filler, called solder, melts. When it solidifies, it is bonded to the metal parts and joins them. The bond is not as strong as a brazed joint or welded one. The base metal doesn’t melt but the solder filler does.

  • Strand Anneal
    • A heat treatment to soften wires which have become work hardened. The strand of wire is continuously passed from reel to reel through an atmosphere controlled furnace, the speed and temperature of which can be varied to suit the material. Annealing via this method overcomes the problem of wire sticking together during the process. It is mostly used to anneal fine wires for chain making which will be supplied on reels.

  • Stress Corrosion Cracking
    • A defect which appears in metal which has been cold worked. It is caused by a deformation of the molecular structure which brings about internal stresses within the alloy causing it to subsequently crack. It can be avoided by stress relief annealing which removes the unwanted stresses with a minimal loss of hardness in the alloy.



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