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CCSA Queries about Lead in Glazes29 Feb 2008
CCSA Queries About Lead in Glazes There has been a flurry of queries on the CCSA website about safety of lead in glazes following a TV program in the States. There is a lot of misinformed comment around this issue causing perceptions of danger which could damage the industry. There is more detailed information in the Health & Safety section but the following highlights the most important points. At Cromartie we want our customers to be fully informed of the facts, we do not consider this just an opportunity to sell more glaze. Advice to Studios As alternatives to the food safe glazes you may be using we offer Gare NTG9000 and Duncan CN2000 lead free glazes. Both are in stock and have been extensively used for many years. If approached by the media or concerned customers and staff, explain the technical points listed below and refer them to our website Health & Safety section or direct to Cromartie. Print off our notes on Lead in Glazes for interested customers and staff. Putting up Lead Free Studio notices is more likely to draw attention to the issue and send the wrong messages to your customers. MSDS (Health & Safety Data sheets) are available to download from our website but be aware that the format of these sheets is not very user friendly and can be misinterpreted. Read them in conjunction with our notes on Labelling Lead glazes. If you have any concerns over lead in glazes please talk to us. Important Technical Points All Duncan and Gare food safe glazes sold by Cromartie contain lead in a “fritted” form. The fritting process involves melting lead with silica (sand) so that it is permanently fused together. This renders the lead “non-bioavailable” meaning it is not readily absorbed into the body by ingestion, inhalation or through the skin. Chemical analysis of the glaze or dust produced by the glaze will show substantial levels of lead but will not show the way that the lead is encapsulated by silica in the mixture, just the separate elements present. Thus a safe glaze will appear toxic. Full lead crystal glass contains the same level of lead as our glazes, we are all happy to drink from them. Lead makes glass sparkle and makes a glaze more forgiving in the firing, smoothing more easily and having a wider firing band. There is no such thing as dust “full of lead” being produced during the firing. In the fritted form lead is stable in the firing, no lead fumes are produced from lead frits unless fired to1200°C – way outside the firing range of our glazes. We are happy to supply several excellent lead-free Duncan and Gare glazes which are available from our stock. Lead-free glazes are a little less forgiving so it is necessary to be more precise about firing temperature and glaze viscosity. Ken Shelton 28 Feb 2008 Comment posting is off |