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.