Oil paintings often become dull and soiled, especially older oil paintings on canvas. This can occur when paintings are stored in a dusty attic or a room that isn't temperature controlled. Paintings that need restoration can become like new again with a little care, specific materials and a lot of patience.
Make sure the painting is dry and that you are in a dry, well-lit working area. Take a large paintbrush and carefully sweep it over the canvas oil painting. This will help loosen up any dirt on the surface of the canvas. Make sure to brush around the edges and in crevices. You can also use the small and medium sized brushes for this if necessary.
Use a soft cloth and carefully wipe over the canvas, making sure not to use too much pressure. Do not get this cloth wet, especially with water or soap. This could potentially ruin the painting.
Examine the oil painting. If it appears yellow or is cracking, there is a varnish over the oil paint. If this is the case, soak a clean cloth in varnish remover. Squeeze any extra liquid from the cloth until just damp. Wipe the painting with the cloth firmly but gently in a rolling manner. Do not press hard on the canvas or it may stretch. If you notice paint coming off onto the cloth, use less pressure and do not touch that area again.
Dip a small paintbrush in varnish remover and tap the bristles to remove any extra liquid. Sweep this over the canvas in small areas. This will take time and patience as you want to work in small sections comprised of only a few inches to completely remove the varnish. Put careful but firm pressure onto the painting with the brush.
Let the canvas dry completely.
Examine the painting again. Look to see where the actual oil paint colours are chipped, faded or cracked. Make sure you have these exact oil paint colours. With the smaller paintbrush, repaint small areas of the canvas where the oil paint has faded, using the same colours. Use small strokes and stay inside the lines as much as possible, using a magnifying glass if necessary.
Let the paint dry completely. To complete the restoration, sweep a coat of fresh varnish over the painting and let dry.