Antique oil paintings often have cracks across their surface caused from the paint drying out over many years. If you have an oil painting you wish to give an aged look to, you can make the surface of an oil painting crack with the application of a specially designed "crackling" medium. The ageing technique involves applying two specially formulated varnish-type coatings, available in a kit at art supply stores, that will give your painting the cracked and aged appearance you desire.
Brush the painting with a dry paint brush to remove any dust. Carefully inspect the surface of the painting to be certain there are no bristles left from cleaning the painting with the brush.
Apply the crackle medium to the surface of the painting with the paintbrush, according to the manufacturer's instructions. Cover the entire surface evenly with uniform strokes. Allow to dry completely.
Apply the ageing varnish over the dried crackle medium. As the ageing varnish dries, you will see the lines caused by the crackling varnish begin to darken. If the lines are not dark enough, after the ageing varnish has dried completely, you can apply a second coat of ageing varnish provided the manufacturer does not discourage it.
Be sure you select a crackling medium designed specifically for oil-based paints.