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HANDBOOK ON FINISHING (Other types of finishing processes :confetti_ball:,…
HANDBOOK ON FINISHING
Other types of finishing processes
:confetti_ball:
Jewellery pieces are offered to the customer with a surface texture, required by the specific design
The fundamental difference between hand-working and machine working lies in the precision of forms and patterns that can be obtained.
Machine work can always be recognised from the perfect replication of the decoration, the sharpness of the edges etc.
Refer to engraving, florentine finish, hammering, faceting and other types of decoration
Among the modern finishing processes should mention surface finishing by laser
*Electroplating
:fire:*
ELECTRODEPOSITION OF GOLD AND GOLD ALLOYS
"White gold" is a general term used to call colored gold alloys.
white
Such as Platinum, Chromium, Cobalt, Sangka, Tin, Silver and Iron etc. Each type of metal has different advantages and disadvantages. Some make metal The mixture is harder and harder to operate and has cracking problems during heating and dulling etc.
RHODIUM PLATING OF GOLD ALLOYS
Rhodium is a metal of the platinum family with a good white colour, a
high reflectivity, does not oxidise or tarnish and can be easily polished.
Rhodium plating, like all galvanic plating operations, requires that the
pieces to be plated be thoroughly cleaned.
“MASKING” OF THE SURFACES
“Masking” is carried out when specific areas of the surface of the
jewellery pieces should not be coated during the electroplating process. In practice, the areas not to be electroplated are covered with appropriate
CHARACTERISTICS OF GALVANIC COATINGS AND
DEFECTS THAT CAN OCCUR
these galvanic coatings will not be continuous on the microscale and will contain some interdendritic porosity. The amount of porosity will be related to the plating conditions and reduces with increasing coating thickness. Galvanic coatings may also be internally stressed and tend to crack as coating thickness increases. Commercial plating salts often contain special additives to control internal stress
formation, to reduce porosity and to promote continuous bright coatings.
Gold alloys and their behaviour in finishing
:star:
general correlations between caratage and composition of gold alloys
Pure annealed 24 ct gold is very soft and ductile and will polish differently from age-hardened 18 carat gold, for example. In general, harder metals polish better than soft ones.
In the case of electrochemical polishing
there are specific electrical parameters that should be defined and adjusted for each alloy to get the best results.
In the case of mechanical finishing
that each alloy has its own mechanical property characteristics (e.g. hardness)
Concluding remarks
: :tada:
Secondly, the speed of finishing needs to match the rate of production of the jewellery product
if the product is gold chain, which is manufactured at high speed, it can be advisable to consider use of electrochemical polishing
In all other cases
In all other cases
The main finishing processes used in gold jewellery manufacture have been reviewed
manual
mechanised
electroplating
electrochemical
Chemical finishing: ‘bombing’
: :explode:
“Bombing” was widely used in both small and large gold jewellery manufacturing workshops
is not a true finishing process, but rather a part of it. It is a way to obtain a uniform bright colour and it is carried out on jewellery pieces after the conclusion of all manufacturing operations.
Most precious stones and pearls are not damaged by “bombing”; the exceptions are opal and turquoise, which may be damaged by this process.
(035,059,060)