SUCCESS WITH LUSTERS

Lusters are metal-based transparent overglazes available in rainbow colors. They are applied over gloss, satin and matte glazes as well as porcelain bisque. Beautiful if applied over china paints, lusters can also be applied over other lusters. When fired they are iridescent. Lusters can be used to save streaky or unattractive underglazes or to give a new or different look to a piece. The most popular and perhaps best known luster is Mother of Pearl which has vari-colored appearance after firing. The firing range for lusters is 022 to 017 as recommended by the manufacturer.

How do lusters work?

• Metallic salts, colorings, a reducing agent (usually organic binder such as oil of lavender) and resin are mixed with oil medium.
• Lusters are applied to a glazed surface with a brush.
• During firing, the reducing agent burns out causing localized reduction.
• The oil medium and the resin burn out and leave the metal.
• A thin layer of pure metal is deposited on the glaze.

Concerns when using lusters:

• Dust on ware before application causes an uneven, splotchy look. Your work area should be dust free and you can clean ware with alcohol and let dry before application.
• Essence brush cleaner left on a brush causes the brush to pick up luster from the ware and leaves brush strokes. Let brushes air dry 2-3 hours after cleaning with essence.
• Wet brushes used for lusters cause a streaky look. Let brushes air dry 2-3 hours after cleaning with essence.
• Using the same brush for different colors of luster causes a muddy appearance. Maintain and use separate brushes for each color.
• Too much luster causes a powdery appearance, open/dull spaces between glossy luster areas, blistering or crazing, and brush marks on the luster. Apply 2 even, thin coats.
• Too little luster causes an uneven appearance. Apply 2 even, coatings.
• A piece fired before the luster is dried causes color to disappear/vaporize, white splotches. Let the luster piece dry overnight before firing.
• Overfiring of ware causes weak colors. Use witness cones to verify heatwork on the shelf.
• Underfiring of ware causes lusters to powder-off. Use witness cones to verify heatwork on the shelf.
• Insufficient ventilation causes migration of lusters and contamination of colors. A frosty appearance after firing results from the reaction of oils and fumes. Insure adequate ventilation of kiln by introducing air into kiln, circulating air throughout kiln, and moving fumes from kiln so they cannot deposit on other pieces. Use the Orton Kilnvent to circulate and supply air to the kiln for the best results.

Fumes from lusters include vapors form oils and metallics. These should not be inhaled. Take caution during application to work in a well ventilated area. Crack windows or doors or use an exhaust system or fan. Take caution during firing to ventilate kiln and remove fumes to outdoors.

(Printed with permission of Orton Firing Institute)

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