Grisalla

This technique was used since ancient times to elaborate stained windows and has been improved over the years without considerable change in the basic procedures.

The colors used are obtained by mixing glass powder with pigments derived from metallic oxides, such as iron or cobalt oxides, and agglutinated with some of the substances before mentioned.

The first step consists in evenly covering the piece with a grey or sepia color. Once dry, the background color is removed to expose light areas by means of glaze. Then, the piece is set into the kiln at approximately 600ºC. Next step, translucent shades and finishing touches are applied, including the glaze, and the piece is reheated.

Silver-Yellow can also be used; this ancient procedure gives beautiful silver colors. Since it is not compatible with grisalla, it is applied on the backside of the piece. The resulting shine comes from the fusion of silver nitrate with glass.

As a general rule, the various brands of colours give different shades when reheated in the kiln. Thus, it is recommended to make samples to know the range of hues that can be achieved.