SCREEN Glass and ceramics decoration


Genie in a bottle


Applying images onto glass and ceramic is something for which the UK is renowned, but as manufacture moves offshore, are we in danger of losing our cultural heritage?


hen decorating glass or ceramic, the printing techniques are very similar: all aim to achieve the adhesion of pigment to the surface with sustained colour or performance over a specific time period. Unfortunately, the operating conditions of printed glass and ceramics can be extremely challenging, specifically in relation to mechanical abrasion and resistance to chemicals.


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For many years the favoured technique was to fuse inorganic pigments to the surface at high temperatures. As the environmental impact of the process and pigments make


them fall out of favour, organic pigments that are stuck onto the surface are becoming more popular.


So what is the difference between inorganic and organic pigments?


Inorganic pigments are derived from mineral compounds, normally oxides or salts of one or more metals. They are resistant to temperature, sunlight, chemical and mechanical attack, however they used to be made from lead, cadmium, chrome and other heavy metals. This meant they presented a health and environmental hazard and many of the heavy metals have been substituted with


By Peter Kiddell


Temperatures differ significantly when using either organic or ceramic/glass ink


safer materials.


Organic pigments come from plants, either in their natural state, or when they have been converted into oil and its derivatives. The pigments all contain carbon which means an almost limitless range of colours can be formulated, including vibrant, fluorescent colours. Unfortunately, organic pigments are poor at providing is metallic colour, unlike inorganic pigments that can be a suspension of metal flakes, such as silver, gold, platinum or aluminium.


Transfer Application at Royal Crown Derby (Courtesy Richard Dennis) 14 SCREEN PROCESS AND DIGITAL IMAGING l June 2010


While organic pigments are normally formulated into inks that consist of resins and solvents, or ultra violet systems without solvents, inorganic inks or enamels are a mixture of glass particles (frit) pigment, solvents, waxes or oils and additives. Although it is possible to use metallic pigments in organic resins, with effects similar to enamels, mirror finishes are only possible in specialist applications where the metallic ink is printed on the back of a high gloss plastic


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