The gilding of decorative ceramics has been undertaken for centuries, with the permanence and brightness of gold appealing to designers. Both porcelain and earthenware are commonly decorated with gold, and in the late 1970s it was reported that 5 tonnes of gold were used annually for the decoration of these products. Some wall tiles also have gold decoration. Application techniques include spraying, brushing, banding machines and direct or indirect screen-printing. After application the decorated ware is fired in kiln to fuse the gold to the glaze and hence ensure its permanence. The most important factors affecting coating quality are the composition of applied gold, the state of the surface before application, the thickness of the layer and the firing conditions.
- Acid Gold - developed in 1860s at Mintons, Stoke-on-Trent, England. The glazed surface is etched with dilute hydrofluoric acid prior to application of the gold; the process demands great skill and is used for the decoration only of ware of the highest class.
- Bright Gold or Liquid Gold - is a solution of gold sulphoresinate together with other metal resinates and a bismuth-based flux. It is particularly bright when drawn from the decorating kiln and so needs little further processing. This form of gilding was invented or at least improved by Heinrich Roessler. Rhodium compounds are used to improve the binding to the substrate.
- Burnish Gold or Best Gold - is applied to the ware as a suspension of gold powder in essential oils mixed with lead borosilicate or a bismuth-based flux. This type of gold decoration is dull as taken from the kiln and requires burnishing, usually with agate, to bring out the colour. As the name suggests it is considered the highest quality of gold decoration. One solvent-free burnish gold composition was reported to consist of 10 to 40% gold powder, 2 to 20% polyvinylpyrrolidone, 3 to 30% an aqueous acrylate resin and 5 to 50% water.
- ↑ "Gold In The Pottery Industry. The History And Technology Of Gilding Processes." L.B. Hunt. Gold Bulletin. 12, (3), 116, 1979.
- ↑ "Gold And Lustres For The Ceramic Tile Industry." S.F.Etris. Ceramic Industries 119, (5), 36. 1982.
- ↑ "Comeback Of Gold Decoration? Trends And New Materials For Tile Decoration." K.Abt. Keram.Z. 60, No.1, 2008.
- ↑ "Precious Metal Preparations: Composition, Applications And Special Decorative Effects." E.Groh. Ceramic Forum International. DKG 72,No.3.1995.
- ↑ "Improving Gold Decorating Techniques." L.V.Gerasimova, V.M.Ivanova, E. Yu.Peskova, E.V.Druzhinin. Glass and Ceramics. 48, No.11/12. 1991.
- ↑ "Dictionary Of Ceramics." A.Dodd, D.Murfin. 3rd edition. The Institute Of Minerals. 1994.
- ↑ "Liquid Gold And Other Components Used In Decoration Of Glazed Porcelain And Glass Articles." N.V.Rovinskaya, E.V.Lapitskaya. Glass and Ceramics. 55, No.3/4. 1998.
- ↑ "Burnish Gold Decorating Composition." UK Pat.Appl.GB2216536 A, for Heraeus W.C.,Gmbh.
- Este artículo incorpora texto de la Encyclopædia Britannica de 1911 (dominio público).
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