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Lead in Glazes Why bother with lead in glazes? Lead has been use in ceramics for 3000 years; its unique inter-reaction with colours and the soft shine that it brings to glazes gives brilliance to pottery that cannot be matched. The wide firing range and elastic property that it has on cooling means that lead containing glazes are much more forgiving and less prone to crazing. Lead free glazes demand a more precise firing regime and are much less forgiving hence lead continues to be used throughout the industry. Although raw lead is a hazardous material this does not mean that leaded glazes are automatically a health hazard; all lead containing glazes sold by Cromartie contain the lead in a safe form. Before being combined with other glaze ingredients the lead is melted and chemically combined with silica (glass) in a process called fritting. These glazes are known as “Low Sol” glazes meaning low solubility; in this form the lead cannot readily be dissolved from the glaze and the toxicity is greatly diminished both in handling during the glazing process and after firing. The body does not readily absorb fritted glazes; in the jargon, the lead is not “bio-available”. Fritted lead glazes came into being in the late 1930’s to protect pottery workers from lead poisoning, a common problem in the industry. The health record of the industry was changed almost overnight and by 1944 the number of deaths from lead poisoning was reduced to nil. The ceramics industry has been transformed from one of the most dangerous to one of the safest. Where glazes are supplied and used in a liquid form the safety aspect is enhanced as there is very little dust formed. Where dust is generated by “finger sanding”, smoothing irregularities in the glaze surface, this should be carried out over a smooth surface that can be wiped with a damp cloth. As with all ceramic dust, floors and work surfaces should always be “wet cleaned”. Very little finger sanding is required as these glazes will smooth out most unevenness when they melt in the firing. In summary lead in glazes gives a sparkle and enhances the colours of ceramics just as full lead crystal glass is enhanced by the lead content. Usual common sense housekeeping is all that is required; keep glazing areas clean and tidy, avoid creating dust, wet clean, wash hands with plenty of soap and water after touching glaze and you will have excellent results and no health problems. It is worth saying that at Cromartie we have not had a single instance of health and safety problems with lead in twenty years of supplying leaded glazes. Ken Shelton Further reading- Glazes for the Craft Potter by Harry Fraser. Pub A&C Black ISBN 1-57498-076-9. Ceramic Faults and their Remedies by Harry Fraser. Pub A&C Black ISBN 0-7136-4033-2. The Potter’s Dictionary of Materials and Techniques. By Frank and Janet Hamer pub A&C Black ISBN 0-7136-4418-4
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