How to choose a metal accessory
GUIDE ON HOW TO CHOOSE A METAL ACCESSORY
BASE MATERIAL
Metal accessories for fashion can be made with different materials, depending on the uses and the quality sought:
– Aluminum: Very light, not very resistant and difficult to work. Suitable for very cheap products or for those where lightness is needed.
– Iron: Heavy and cheap material. It oxidizes very easily and, therefore, is not suitable for fashion accessories. It is used in very cheap productions. It is easily detectable with a magnet.
– Zamak (zinc and aluminum alloy): Medium weight material, cheap and easily workable and moldable. Widely used for medium-high quality products. The surface of the piece must be well prepared to get a good result.
– Brass: heavier than zamak and more expensive either as raw or as processed material. It is used for high quality products.
– Steel: being difficult to oxidize and very resistant, it is the material par excellence. Unfortunately, in addition to high costs, it is difficult to work and the surface can only be galvanized with pre-treatments that further increase the price. It is the most suitable material for coloring with PVD treatment.
SURFACE PREPARATION
The surface of the rough pieces must be cleaned and smoothed before the surface coloring (by electroplating, PVD or painting).
The smoother and more perfect it is, the better the quality obtained.
The various stages of preparation are:
– Tumbling (low quality): the pieces are vibrated inside rotating baskets, together with smooth stones.
– Vibratory polishing (medium quality): the pieces are vibrated for certain periods in the vibrators with ceramics of various sizes, and in various steps.
– SISAL polishing (high quality): the items are hand brushed with a rope brush on the various sides.
– “FOAMING” cotton polishing (very high quality): the garments are brushed by hand with a cotton brush on the various sides.
– Acid copper + second polishing (SUPERIOR QUALITY): first polishing + acid copper electroplating (to cover all imperfections) + further polishing. It is the highest quality.
COLORING THROUGH ELECTROPLATING
The articles are colored using an electro-chemical process: they are in fact immersed in a tank containing a formula of water and various products (eg: gold, if you want a gold color), and are passed through by electricity. By electro-deposition, a layer of material contained in the bath is created on the piece (eg gold, if the tank contains gold salts) .The thickness of the deposit depends on the immersion time and the intensity of the electric current that passes through the bath.
Actually, the steps are multiple and happening in different tanks, each containing “its metal”: each “immersion” deposits a layer of material on the surface for a given thickness.
The different layers and various thicknesses determine the “characteristics” of a finish (example: 1 mcn acid copper + 1 mcn alkaline copper + 10 mcn Nickel + 0.5 mcn gold)
There are two types of electroplating:
– TUMBLER: The items are all put together in a basket that rotates in the tub.
The pieces, colliding with each other, will have an imperfect surface. It is used for very small items or for low quality items
– FRAME: the items are tied to a support (frame) with copper wire, separated from each other. The frame is immersed in the tub. In this way the pieces do not collide with one another and the result (surface – color) is perfect.
Quality of the galvanic deposit:
The longer the items remain immersed, the greater the thickness of color deposited, and the greater the resistance over time and therefore the quality of the accessory. But the higher the cost.
– Average quality: about 0.1 microns
– High discrete: about 0.2 / 0.3 microns
– High quality: about 0.5 microns
– Very High: 1 micron and more
(note: 1 micron = 0.001mm)
Nickel: with of free from?
Usually galvanic colors are made on a NICKEL base, which made them more resistant. Unfortunately, contact with Nickel can cause skin irritation, so more and more brands have banned it and require accessories without the presence of nickel (NICKEL-FREE). To obtain the same color resistance without using nickel, however, it is necessary to increase the thickness of the precious base and therefore the final price.
Read our “galvanic finishes list”
Buy our “galvanic finishes folder”
COLORING BY VARNISH
The piece is spray painted, after having properly prepared the surface. The treatment can be by electrostatic painting, i.e. the piece is connected to a negative pole and the sprayed paint is positively charged. In this way the paint is attracted to the piece which is coated in every point, even in the most difficult to reach.
COLORING BY PVD
To meet the growing demands for “green” processes with low environmental impact, PVD treatment is becoming increasingly popular, as a substitute / alternative to galvanic treatments.
In fact, the PVD process does not include “chemical baths” and products to be disposed of.
It consists in bombarding the surface to be treated with precious vapors, in suitable vacuum bells (Physical Vapor Deposit).
This creates an interpenetration of the precious material on the surface of the treated element.
The results are:
AESTHETIC: the surface takes the color of the precious material used (ex. Gold, Palladium or Ruthenium)
MECHANICAL: the treated surface has
– high surface hardness and resistance to wear and rubbing
– resistance to acids and solvents and, in general, to atmospheric agents
(For example, this treatment is also used to treat screwdriver tips).
The best material on which to use the PVD treatment is steel.
The PVD treatment is also excellent as a “base” for subsequent painting: the final coloring is in fact tenaciously clinging to the surface and extremely resistant.
More and more often in the high fashion industry, galvanic colors are “converting” into PVD colors.
The technology is quite new, but new colors are being added every day to the initial ones available (gold and its shades, black and its shades), according to customer needs.