PROJECT DESCRIPTION
BACKGROUND
Over the past decade, the presence of lead in glazes for ceramics has posed health risks for workers exposed to high concentrations, including lead poisoning and neurological problems. Recent studies have also shown that exposure to lead compounds may lead to infertility. Although more restrictions on the use of lead have been introduced, it remains an essential element for glazers. There is therefore a need for non-toxic alternatives to lead glazes.
OBJECTIVES
The main objective of the LEAD-COLOURED LEAD-FREE project was to eliminate lead compounds from the production of glazes with high aesthetic and technical value. The aim was to use a two-stage melting process; replacing lead with boron, while minimising boron volatilisation. To do this, the project set up a pilot system with an innovative melting process, using two different temperature levels for the two stages: a melting stage at low temperature for boron processing and a rotary melting stage for subsequent mixing with other glaze elements. The project set out to assess the options for using this industrial process on a large scale, without increasing costs, in order to make the technique more widely applicable in the ceramics sector. A further goal was to minimise boron losses during the production process, which could jeopardise the environmental benefits arising from the elimination of lead compounds. The project also undertook measures to develop awareness among customers and suppliers about the opportunities for making production processes more eco-sustainable, without reducing the quality of the products or their aesthetic characteristics.
RESULTS
The LEAD-COLOURED LEAD-FREE project succeeded in demonstrating the technical viability of a new melting process able to replace lead with boron in the production of glazes, while minimising boron volatilisation. The operative grinding line and modified kilns are operating at Ceramiche Ascot’s Castelvetro factory. New glazes were created during the project, which have a wide interval of workability. These new samples have shown that the elimination of lead compounds can be achieved without compromising the quality and aesthetic standards of glazed products. More than 1 000 m2 of tiles and grès stoneware were produced by the end of the project, without the use of lead in the manufacturing compounds. Different experimental conditions were used to help optimise the process. The main innovation of the project was the new two-stage melting process, in which a low-flux glass with high boron content is obtained using lower temperature levels that minimise the volatilisation of boron, followed by a higher temperature melting stage in which prepared glass is added gradually in powder form. The project demonstrated in a pilot system that this was technically feasible at an industrial scale. Reductions in the volatilisation of boron were achieved by using a pre-glaze (frit), involving a low-flux oxide mixture that enables the temperature to be kept at levels where the volatility of boron is minimal, and, at the same time, providing either a fluid phase of viscosity low enough to be poured or adding a semi-solid compound at a late stage during the melting process. The lower volatilisation of boron means, firstly, that the need to add excessive quantities of boron compounds into the raw material mixture is no longer required to ensure its presence in the final glass mixture, and secondly, that current boron filtering and reduction systems are able to work longer. In both cases, the result is lower plant engineering and management costs. The low-flux frit with high boron content has a relatively long storage life. This reduces the problems of storing boron generally, which is highly corrosive, has high water solubility and is highly reactive with other materials. The preparation of a high-boron frit therefore stabilises boron and keeps it from being released into the environment when the frit comes into contact with humidity or water, which helps to optimise ceramics production. The long shelf life also protects operators from fluctuations in the price of boron compounds. New glazes, produced from low-flux boron frits and silicate-calcium-sodium glass, substitute lead compounds not only in terms of composition, but also in terms of technology, quality and cost-effectiveness. They have an aesthetically pleasing appearance, and low porosity similar to those produced using lead frits. However, when substituting lead compounds with boron compounds, lighter tiles result. The weight of each tile for residential application is critical when considering buildings with several floors, so the weight of tiles could affect the overall building. Lighter tiles mean lower static loads and the chance to create slimmer structures. Environmental benefits derive from the elimination of lead compounds from the production of glazes, and in minimising the amount of boron required. Calculations suggest that the adoption of the proposed technology at the European level would mean a reduction equal to 131.6 g/year of emissions of lead compounds. The elimination of polluting chemical substances reduces the quantity of materials that require purification, thus reducing the environmental and health impacts of ceramics manufacture. Workers benefit from a safer working environment. The project’s success in eliminating lead compounds and minimising boron volatilisation contributes to meeting targets set in the EU regulation on Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH). The new pilot system can be potentially replicated all over Europe. There are no geographical limitations to the project’s methodology and the process only requires a few production plant modifications. The boron compounds have costs that are lower than barium compounds (currently used for the most part in leadless frits in the market). In addition, the new process minimises boron losses in the kiln, resulting in additional savings. The application of the method proposed reduces the production costs (lower plant engineering & management costs). In addition, the project demonstrated that there is a real opportunity in creating a market for the project product that appears to be suitable as substitute of raw materials.
Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).
