Lustre Colours may be applied and fired on glazed china and earthenware to produce a unique and appealing decoration of metallic tints. However it is important to observe some elementary rules.
For best results the lustre should be applied with a flat brush, evenly and in medium strength, for too heavy a deposit will cause blistering or flaking in the firing and uneven coatings will tend to cause colour variations. The exception is with respect to Mother of Pearl lustre, which should be applied in a cross-cross manner and subsequently stippled to bring out the mottled effects characteristic of Mother of Pearl.
Because of their basic ingredients lustres will vary in viscosity and workability. Those that appear thick and tacky can be conditioned by adding a few drops of Lustre Thinning Essence. Lustres may also be thinned further and applied by spraying.
The ideal firing temperature in any particular kiln is best determined by experience but the following temperature ranges will be useful as an initial guide.
Bone China 680-760°C
These are the top temperatures and should be approached slowly during the "smoking off" stage. Ideally the kiln door should be left open slightly until the ware has smoked off, but above 500°C, the door should be closed and the ware fired to maturity. The kiln may be switched off immediately top temperature is reached, or may be held at temperature for a soaking period of about 30 minutes. The actual temperature depends on the ware itself, harder glazed ware will require a slightly higher temperature than soft glazed ware. The principle is to fire as high as the ware will stand. If under-fired the decoration will wipe off and if over-fired will sink into the glaze and lose its appeal.
Another point to remember is that the kiln should not be crowded with too much ware. Allow sufficient air space to permit the complete burning off of the combustible matter in the lustres.