Perhaps lurking in your attic somewhere is an old oil painting -- a family heirloom you think has some value. Or you spy an epic landscape oil painting at the neighbourhood garage sale that you believe may be worth something. Determining its value is helpful for many reasons, such as for insurance purposes, possible donation to a museum or to sell outright on your own in the current art market. Before you go running off to the local art gallery for an opinion, do research first. The bottom line: if you do your research and get the best determination of the value of the oil painting, you could be money ahead in an investment or generate some needed cash.
Gather provenance information about the painting. Where has it been since its origin? Is there a family history or has it been documented in other establishments? Tracing the history of the object up to the present will help confirm and establish a value of the piece. Keep the documents together for easy reference.
Determine if it is really an oil painting. In most art markets, oil paintings tend to have more value than acrylic paintings, and are easily confused by the untrained eye. For the most part, an acrylic painting will dry leaving a flat finish and an oil painting will dry leaving signs of brushstrokes. Many media can be added to thicken acrylic paint to simulate the appearance of oil, which makes it more difficult to distinguish between the two; however, an expert should be able to distinguish between them. Acrylic paint is also relatively new to the world of painting, only introduced about 60 years ago by such artists as Rothko and Lichtenstein. If your painting is older than 60 years old it was probably done in oil, which will increase its value.
Do a quick evaluation. Is the oil painting signed? What is the composition of the work? Are there other distinguishing marks or attributions?
Take digital photos of the oil painting. One photo should be of the entire piece. Get close-up shots of the artist's signature as well as any other distinguishing attributes, such as the texture of the paint on canvas. If your artwork isn't too portable, having quality digital photos is the next best thing. Also, you can e-mail digital photos to out-of-town markets or appraisers.
Find an expert who can identify characteristics of an oil painting, preferably from a local museum or college. Be wary of galleries or other places that sell artworks for commission. Their opinion may be biased depending on if they want to purchase the artwork or sell it on consignment.
Find an appraiser. Usually an appraiser is the best option to determine value in current market conditions. An insurance agent should be able to refer an art appraiser, or check with your local art museum. Ideally, ask if they are accredited by the International Society of Appraisers (ISA) or American Society of Appraisers (ASA). Before agreeing to an appraisal, ask about any upfront fees. If the artist is fairly well known, try looking up auction prices for similar pieces on your own.
Keep the painting in the original frame if possible.
Do not have the painting altered or even cleaned until an appraisal or evaluation is done. This could seriously affect the value of the painting.