Onglaze colours without heavy metals

Pigment & Resin Technology

ISSN: 0369-9420

Article publication date: 1 August 1998

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Keywords

Citation

(1998), "Onglaze colours without heavy metals", Pigment & Resin Technology, Vol. 27 No. 4. https://doi.org/10.1108/prt.1998.12927dad.019

Publisher

:

Emerald Group Publishing Limited

Copyright © 1998, MCB UP Limited


Onglaze colours without heavy metals

Onglaze colours without heavy metals

Keywords Colour, Glazes, Heavy metals, Heraeus, Pottery

At the Ceramitec fair in Munich W.C. Heraeus introduced a new range of onglaze colours, produced without any addition of lead or cadmium. They are especially developed for the decoration of bone china, vitreous china and earthenware. All 24 basic colours are reported to have a high colour intensity, very good printing properties and are acid and dishwasher resistant. The series H 56 is said to be particularly suited for the decoration of most types of ware used in the home, hotels and restaurants. They are all not suitable for use on porcelain.

Onglaze colours of the series H 56 are especially suited for the decoration of soft glazes with a thermal expansion coefficient of 65 to 90 x 10­7K­1. Depending on the glaze, soak time and the total firing cycle they can be fired between 700°C (1,292°F) and 900°C (1,652°F).

The carefully controlled grain size distribution of the colours guarantees optimum printing quality and ease of ink production; 90 per cent of the colour particles are smaller than 12 micrometer, 99 per cent smaller than 18 micrometer.

Onglaze colours of the series H 56 are produced without any addition of lead and cadmium. The trace contamination of lead oxide amounts to less than 0.2 per cent. Correctly processed and fired decorations are resistant according to DIN 51031/32. The heavy metal release of fired decorations lies usually under 0.001 mg lead/dm2 and under 0.00002 mg cadmium/dm2.

In testing the series, the decorations, produced with the H 56 colours, had a high alkali and acetic acid resistance. Even after 1,000 washing cycles in a dishwashing machine the decorations showed no attack. Therefore they belong to the category "dishwasher resistant".

The cobalt blue H 56115 deserves special attention. The colour intensity of this blue is said to be extraordinary for an onglaze colour. The blue reaches when overprinted with the flux H 56050, the alkali and acetic acid resistance of the other colours of the series. Purple mixed with mandarin orange gives beautiful red shades.

For further details contact W.C. Heraeus GmbH, Germany. Tel. + +6181/35-381; Fax + +6181/35-5261.

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