Metal Release
Regulations have existed since the late 1960s to protect consumers from the potential risk of toxic materials, mainly metals, being released from glazes into drink and foodstuffs. Lead and cadmium are the metals of greatest concern, although testing can be extended to include others. The propensity for any glaze to release metal may depend on complex interactions between the formulation used, any applied decoration and the kiln atmosphere.
Monitoring the level of metal release from glazed ware forms part of the Quality control procedures of all reputable producers. Test methods are specified according national and international standards, although testing usually involves: the ware being immersed or filled with a 4% acetic acid solution; covered and left for 24 hours at room temperature, although if cooking ware is being tested higher temperatures are needed; the acetic acid solution decanted from the ware and the concentration of leached metal measured by Atomic absorption spectroscopy. Acceptance limits are enforced by legislation, and whilst varying between countries all are within the ppm range. Some of the most well recognised legislation are: across Europe 'EC Directive 84/500/EEC 1984'; for the UK 'GB Ceramic Ware (Safety) Regulations SI 1647, 1988'; and for the USA 'FDA Compliance Policy Guide 7117.06 and 7117.07 for cadmium and lead.'
Read more about this topic: Glaze Defects
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