Onyx was known in Biblical history as alabaster and has been used as a decorative material for centuries. It is crystalline in structure and translucent with soft delicate bands and a cloudiness of amber, red-orange and green. It is entitled to be classed among the most decorative stones. Normally the ground color is white but almost invariably veined by an unequal distribution of the coloring, or by the subsequent infiltration of metallic oxides during its stalagmitic formation, i.e., stalagmites and stalactites.
I make no apologies for including the background information in my articles. I am of the opinion that without history, there is no future for craftsmanship. I meet many people who are interested in decorative paintwork and all of its facets - not only as a recipe to extend their skills but also to gain knowledge that wasn't available to them in earlier training.
Algerian Green Onyx
My technique is designed to produce a transparent effect by integrating water-based under-painting with veins in oil media. The process can be completed using a large surface such as block work.
The ground color can be based on Benjamin Moore #486 satin eggshell to a smooth hard finish. The color can be varied according to the scheme, but the same tone value should be used, and it must be free of brush marks or roller texture like orange peel.
Hint: Rub a thin coat of Penetrol into the dry surface. Wipe off the surface with a dry cloth to pick up any excess. This will seal the Acrylic and create a non-absorbent surface for the water-based glaze.
Tools & Materials Required:
Acrylic Scumble Glaze
Acrylic Green Satin Paint
Black & Burnt Sienna Tints
White Acrylic Primer Undercoat
Clean Lint-Free Rags
Pointed Sable Writer
White Undercoat Tube Oil Colors: burnt sienna, burnt umber, yellow chrome
Pale Oil Varnish
Step 1: Rub over the panel with a damp sponge and Rottenstone powder to eliminate cissing. Coat with a thin, even film of weak acrylic glaze. Add a small quantity of black tint to acrylic glaze and apply patches at random with a soaked piece of rag or a feather. Add small areas of burnt sienna as illustrated and soften all edges with the Badger. Allow to dry thoroughly.
Step 2: Coat the dry panel with a film of Acrylic Scumble glaze followed by a thinned white acrylic undercoat and using a large feather in areas as illustrated. Carefully soften all edges while wet with a Badger brush and allow to dry thoroughly.
Step 3: Wipe over the panel with a thin film of Penetrol. Use the oil rage with a small amount of chrome yellow and raw sienna tube oil color to wipe over the white areas of the panel and soften into the background.
Step 4: While the panel is wet, and with three colors on the palette - i.e., small quantity of the ground color, burnt sienna and burnt umber tube oil colors - sketch in the structure of the veins with mixtures of the colors. Soften carefully to give the illusion of the veins in a transparent ground, strengthening other areas. Complete the work with an extra pale (no yellow cast) oil varnish to enhance the effect of the translucency.
Courtesy of the The Faux Finisher and the Paint and Decorating Retailers Association - www.pdra.org