The central point of this decorative technique is the method of welding the granules to the underlying surface; in summary it consists in exploiting the properties of the generically called "copper salts"
In reality, these are copper oxides, sulphates or carbonates found in nature in various crystalline forms such as malachite, azurite and cuprite. All three forms are effective for welding the granules, naturally each craftsman uses them in various solutions and mixtures according to their own personal recipes.
Copper salts have the property of retransforming or reducing into metallic copper through high temperature in a reducing environment, i.e. in the absence of oxygen. These salts, arranged between the granules and the surface on which they rest, concentrate by capillarity between and under the granules, and once the object is brought to a temperature of 900°C, the salts are reduced to metallic copper, entering the alloy surface of the granules and on the surface with which they are in contact, creating a liquid film which solidifies by gradually lowering the temperature. In this way the granules remain perfectly welded in an imperceptible way to the eye, giving the impression of only being placed on the surface of the jewel. Wires, foils and other parts of the object are usually welded in this way.
