Pavlína Volfová
<Pavlina.Volfova@preciosa.com>

Environmentally friendly crystal and coloured glass
Květa Sázavová & Pavlína Volfová
Preciosa, a.s., Opletalova 3197/17, 466 01 Jablonec nad Nisou, Czech Republic

Preciosa is a leading international glass manufacturer and supplier of machine-cut crystal components. It primarily produces semi-finished products for the fashion jewellery and garment industries. The most popular products include crystal chatons, chaton roses, and glass beads. Our company believes in supporting the preservation of the environment and utilizes ecologically responsible technologies.

Preciosa has own R&D department for applied development of glass. We develop new glass colours, modify the glass composition for new processing technologies, and also eliminate toxic and polluting compounds from the compositions of the glass. Removed compounds have to be replaced by other oxides in order to achieve the same properties and, predominantly, the same colours of the glass.

The glass components PbO, As2O3 and CrVI+ have been regarded as environmentally harmful and therefore we produce lead-free, arsenic-free and chrome-free glass. PbO is a compound that is important to achieve the desired optical properties, and As2O3 has been used as a refining agent, now it is replaced with antimony. Nowadays our research is focused on red glass. The red colour is caused by the cadmium based Cd(S, Se) pigment after heat treatment. However, as cadmium is toxic to humans and hazardous to the environment, we try to achieve the red colour with another colouring compound. An alternative, the copper ruby, represents a clear deep red glass containing metallic copper in crystals of colloidal size. In ruby glass the colour is achieved by heat treatment.

Crystal glass has been developed having a refractive index higher than 1.53 and a high mechanical strength, free of any content of compounds of lead, barium and arsenic and guaranteeing maximum health safety. The base glass composition is alkaline-calcium, which is modified by ZnO, TiO2 and ZrO2 oxides. Refractive index increases with Li2O and CaO oxides.