GLAZE-Hungarian potter FERENC HALMOS creates matt crystalline glazes avoiding barium carbonate. Occasionally I have seen potters 'bathing' in glazes containing barium carbonate (BaCO_3) without any protective gloves, or worse still, spraying a glaze without wearing a face mask. This is a very dangerous way of production because of the toxic characteristic of the slighty water soluble barium carbonate. (This material was used to kill rats). But in the ceramics recipe books it is rare to find matt crystalline glaze compositions without barium carbonate. In my recent research I have found new ways of creating matt crystalline glazes, having experimented with them for the last fifteen years. Numerous ground materials have been tested in my recipes, which now total more than 1500 glazes. At the beginning I was lucky to get two nice crystalline pieces out of twenty. Although still risky, the results now are much better, with an 80 percent success rate. However, sometimes a mistake results in new possibilities. It happened by accident some years ago when the electric power supply was interrupted suddenly while I was firing crystalline glazed vases. Unfortunately the firing was at the stage where the temperature had to be held at 1800deg C for four hours in order to produce nice big crystals with high glass. The supply returned only a few hours later when the temperature has fallen to 660 deg C. When I looked for a second into the kiln I saw only a few small (1-3cm) crystals on the vases and thought it best to take no more risks in improving the glaze. So I reheated the kiln to 1150 deg C and then cooled 750 deg C per hour to 1000 deg C and then finished the programme.
展开▼
