Ceramics - How it's made | Ceramic Tiles

 

GLAZING .. continued....

The various methods of coating biscuit tiles with glaze may be reduced to the two heads of machine glazing and hand glazing. Naturally the former is used for classes of tiles produced in bulk, such as white glazed tiles, and the latter for those made in smaller quantities, more particularly those in which a mottled effect is required. 

White-glazing by the waterfall process

Most of our machine glazing of white tiles is carried out on the "waterfall" principle. 
Over a horizontal traveling wire belt is placed a vessel at the bottom of which is a long fine slot at right angles to the belt. The vessel is kept constantly supplied with liquid glaze of milky consistency, which escapes through the slot and falls in the form of a thin sheet. Through this sheet the wire belt carries a constant stream of tiles, so that their faces – turned upwards – become coated with glaze. As most of the glaze's moisture is almost instantly absorbed by the porous biscuit, the handling of the newly-glazed tiles, though requiring care, presents no serious difficulty. 

Another mechanical – or semi-mechanical – method of glazing is that of aerographing, or air- 
pressure spraying, which we use for our "Recesso" fittings and for stencilled borders. The 
latter, in fact, are doubly aerographed, the "under-glaze" black or colour of the pattern being sprayed on through a stencil, and, the stencil removed, a colourless transparent glaze similarly applied over the whole face of the tile.  

Mottling and Dipping

Of the hand-glazing methods the simplest is that of "dipping," in which the tile's face, held downwards, is brought momentarily into contact with the surface of some glaze contained in a bowl or similar 
vessel. Most of our mottled effects are produced by the use of two or more different-coloured glazes, the ground colour being usually applied by dipping, and small quantities of the mottling colour or colours by being dabbed on here and there with a sponge. There are, however, a great many "tricks of the trade" used in mottling – such, for instance, as dipping a tile in glaze A, mottling over this with olive 
oil (which will evaporate on firing), and finally dipping in glaze B, which last will provide the mottle by "taking" only where the oil has not touched the first glaze. 

Majolica Colouring. Handpainting. Tubelining 

In the case of embossed tiles, such as key-pattern and chequer borders, the different-coloured glazes are applied to their respective parts of the tile with camel-hair brushes, the raised lines of the pattern preventing them from flowing into one another. Tube-lined tiles are glazed in the same way, but in their case the biscuit itself is flat, the raised lines being formed of a thin clay mixture applied – immediately prior to glazing – exactly as lines of icing sugar are applied to cakes. 

Handpainting – as the term is understood in the tile industry – is freehand painting in oil colours on the fired-on glaze. Its decorative possibilities are almost unlimited, being, in fact, akin to those of oil- 
painting on canvas. Hand-painted tiles undergo no less than three firings, the final one to fuse the colours into the glaze to which they have been applied. 

 

Colour-glazing 'Armitage' sanitary ware
for Edward Johns & Co. Ltd.

Apart from our products a certain amount of "Armitage" sanitary ware is glazed by us, in extremely beautiful shades of mottled green, blue, grey, and amber, for our associated house of Edward Johns & Co. 
The glazes used blend perfectly with those of our corresponding tile series – a fact which has given rise in Richards – Johns bathrooms to a perfection of harmony not readily to be obtained with components from unrelated sources. 

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From: "A Century of Progress 1837-1937" a publication to commemorate The Centenary of Richards Tiles Ltd.