The appearance of Roman gold when it comes from the kiln is Matt or dull. In order to bring out its natural brilliancy, scouring or burnishing is necessary. This can be done with a spun glass brush made for this purpose, or it can be burnished with a special sand. In case an article has to be refired, be sure to remove all of the glass fibres as they would ruin the decorations. The beauty of the unburnished gold will be destroyed by moisture from the fingers. If sand is used, moisten a soft cloth with water, and after dipping it in sand, rub the gold gently. After the gold is polished, the china can be washed. The china is underfired if the gold comes off in burnishing. The gold can be burnished more easily and more evenly if a coat of liquid gold is used in the first firing and Roman gold on the second.
LUSTRES
Cleanliness is one of the first requisites for success in using lustres. The brushes should be cleansed with Gold-Essence or Alcohol from all traces of one color before using another, and should not be allowed to dry containing any color. The corks should never be changed from one vial to another as the least contact of tints in the unfired state is liable to spoil the whole vial. The vial should be corked at once when not in use as the liquid evaporates rapidly; this will also guard against dust and upsetting.
A soft camel’s-hair brush, that can be dipped into the vial, will be needed; also a wad of cotton enclosed in a piece of silk to form a pad as for ordinary tinting.
Use great care in handling pieces tinted with lustre colors. Clean the china thoroughly, using alcohol, being careful to leave no finger marks on the piece. Dust in the brush, in the kiln or on the china will make blemishes. See that the work is not exposed to any dampness. After the work is completed handle as little as possible and if necessary to be wrapped, use tissue paper, not cotton. It is best to apply the lustre in the last firings. An even tint is obtained by several applications, but always fire for each application of the lustre. A second coat on an unfired coat of lustre will produce a blotchy effect.
If lustre has fired spotty or in an unsatisfactory manner the fault can usually be corrected by applying another wash of the same color or a darker tint. A generous application of Mother of Pearl lustre will also remedy the defect. If lustre should fire too light, apply another wash of the same color and refire.
Lustres dry quickly and therefore should be padded without delay. Always have the dabber ready so that there will be no time lost after the color is applied. A good plan would be to apply lustre over a part of the surface and quickly pad it smoothly, then apply the lustre over the balance and finish by padding. To retard drying, mix a very little oil of lavender with the lustre, on the palette. This will also assist in padding the lustre more successfully. It is difficult to apply lustre smoothly with a brush inside of cups and small bowls. To obviate this pour a small quantity into the bowl and spread it with a silk dabber. Be sure that the lint has been singed from dabber. Firing of lustres require a great deal of care. The piece should be placed in the kiln in such a way that no dust can fall on it. Be careful in drying lustres as the color will pulverize if the heat is too strong. On lustre and gold decorations care must be exercised in burnishing the gold so as not to rub the lustre, as it is very easily scratched. Lustre applied too thick is liable to crack and if applied over fired color will lose its brilliancy unless the color is a very light tint. Fired tints and lustres can be removed with hydrofluoric acid.
Lustres should have a medium fire. Deep color effects are obtained by repeated applications and firings. If lustre color is to be applied over gold, see that the gold is burnished. It is not advisable to apply painting colors over lustres as the combination is not a success. Lustres applied over fired Matt colors will produce a rich metallic effect which harmonizes beautifully with gold and paste work. A variety of metallic effects can also be obtained by applying a greenish bronze tone. Ruby will produce a strong dark metallic effect, and orange over gold produces a bluish purple bronze tone. Lustres applied over liquid bright gold will be very brilliant, but richer effects are obtained over Roman gold.