Q: How can I age an oil painting surface to make it look old?
Very old paintings can yellow over time. Colors may also fade if they
are not archival. Without damaging your artwork, you may want to thinly
glaze your artwork with either burnt umber or sienna. The glaze is one
part turpentine to two parts linseed oil with very little oil paint.
Try testing this on a corner of the painting first. You can apply this
mixture with a soft cloth, and it can be removed easily if wiped off
--by Camille LaPointe-Lyons