Prepare the areas of the mantel you want to antique. Typically, gold leaf would be applied on borders, trim and scrollwork, rather than the entire mantel. Remove any existing paint or lacquer from these areas with a commercial paint or lacquer remover, following the instructions on the package.
Sand the areas with 100-grit sandpaper to remove remaining traces of paint or lacquer.
Use a paintbrush to apply a coat of liquid gold leaf to the selected areas. Allow it to dry thoroughly.
Brush burnt umber paint over the gold leaf, working in small sections. After painting each section, immediately wipe off the burnt umber paint in a single stroke with a paper towel. Small areas of burnt umber will remain in the mantel’s scrollwork and crevices, simulating tarnished gold leaf. If you prefer a lightly tarnished look, you may stop at this point. To create the illusion of flaked-off gold leaf, allow the burnt umber paint to dry for two hours and continue to Step 5.
Paint over the gold leaf lightly with brick-red acrylic paint. This simulates the clay bore applied under gold leaf. Allow it to dry for two hours.
Apply an acrylic paint color of your choice in the crevices and corners of the gold-leafed area and allow it to dry for two hours. This simulates the mantel's original paint application.
Rub the painted area gently with a wet rag to expose the underlying layers. This will create the illusion of gold leaf worn away to reveal the underlying clay bole and original paint. Rinse the rag frequently to avoid muddying the colors. Allow the area to dry thoroughly.
Rub ochre wax into scrollwork and crevices to create the illusion of accumulated grime.