Is tung oil safe for antique furniture? No, not really.

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In the late 1980s, the Journal of the American Institute for Conservation published an article about the contents of historical furniture finishes. It identified five main components of various historical finishes: tree resins, insect resins, oils, gums and waxes. Tree resins, such as from pine trees, are often used to make varnish. Insect resins, such as that from the lac beetle, are used to make shellac. Boiled linseed oil and oil from the tung tree are common oil finishes. Gum is another product from trees and is used as a binder. Waxes are primarily beeswax and the much harder carnauba wax.

Furniture Detective by Fred Taylor

But somehow, in the American viewpoint of furniture care and maintenance, the only part of this variety of finishes that seems to have been retained is the “oil” part – and not as a finish component but as a maintenance vehicle. Virtually every commercially advertised household furniture care product proudly touts among its contents such ingredients as “lemon oil” or more recently “orange oil.” While lemon oil and orange oil do in fact exist, what, if anything, do they have to do with the maintenance of furniture finishes?

The oils of various citrus products are derived by the process of cold pressing or low heat rendering of the skins of the fruit. This gives a concentrated concoction of natural oil that is highly acidic. It is a natural, safe degreaser and as such has a useful place in some household and commercial cleaning applications. It is especially appropriate in hand cleaners where a non-toxic degreaser is desirable instead of the traditional petroleum distillate degreasers such as mineral spirits or naphtha. It is also appropriate when there are sensitivity questions or environmental issues about the use and disposal of petroleum products.

But that is as far as it goes. Lemon oil, in an appropriate concentration, is a cleaner. Period. The same goes for orange oil. These oils have no magical properties that lend extended life or beauty to wood or its finishes. You have only to read the advertisements for some of these products to realize the lack of understanding of furniture finishes on the part of the vendors. For example, one famous lemon oil product which also contains carnauba wax,  says in its ad that it “treats the wood and enriches the beauty of the grain.” How can it “treat” the wood if it never touches the wood through the finish? The same manufacturer has a “cabinet and panel treatment” which it claims has “higher absorption by the wood resulting in higher preservation.” Yet there is nothing in the product that will penetrate the modern lacquer, shellac or urethane finish found on most cabinetwork. So how can it lead to “higher absorption by the wood” if it never reaches the wood?

Is tung oil safe for antique furniture?Tung oil has its place in furniture finishing, but not in long-term furniture care as it will damage existing furniture finishes over time. Photo courtesy www.woodcfraft.com

Another highly advertised product, The ___ Solution, claims to be a mixture of beeswax, lemon oil and a specially designed mineral base oil. It then claims that the product is a “true wood feeder that is fed into the wood during application.”

The last time I looked, the wood in my antique furniture had been dead for some time and no longer required feeding of any sort. What it needs is protection from too much or too little atmospheric moisture, accomplished by a surface finish.

But commercial products are not the only perpetrators of myths about oil on furniture. The literature and the Internet are full of home recipes for furniture polish. One online guru states that while the traditional recipe for a good polish calls for 1/4 cup of linseed or vegetable oil and a few drops of vinegar, she prefers the opposite, 1/4 cup of vinegar and a few drops of oil since in warm weather the oil may get rancid! She then states “The vinegar pulls the dirt out of the wood and the few drops of oil lubricates the wood so that it doesn’t dry out.” Lubricates the wood? Was it squeaking? No amount of oil will keep wood from drying out when the relative humidity is below 30 percent.

Another “expert” on a vegetarian food page suggests a furniture polish/dust remover made of 1/2 cup lemon juice and 1/2 cup olive oil. Maybe she should stick to cooking because she sure doesn’t know anything about furniture polish or finishes.

The problem with oil – any kind of oil applied to finished surface – is what happens next. There are basically two kinds of oil: drying and non-drying. The non-drying is the least harmful initially since it doesn’t undergo a chemical reaction. The most common non-drying oils are lemon oil, orange oil and mineral oil. These oils have a very slow evaporation rate and remain on the surface in a microscopically thin semi liquid state for days – even weeks – after application. As a result, they produce a surface that smears easily and accumulates every particle of dust, pollen and pollution that passes its way. The build up eventually must be removed.

Drying oils such as tung oil or linseed oil are especially harmful since they actually undergo a chemical change as they dry and attempt to bond chemically with the surface. As they become hard through oxidation, they become difficult to remove and over time the accumulation of layers of dried oil forms a shell over the old finish and eventually turns dark, obscuring the original surface.

The fact is, unless the original finish of a piece of furniture was an oil finish, then oil has no place on a piece of furniture. Think of the finish on your furniture as the finish on your car. They are both coatings designed to protect the basic structure underneath, whether it’s steel or wood. They are designed not to allow moisture or dirt or grease to touch the primary surface.

You don’t oil the paint on your car. Neither should you oil the finish on your furniture. Use a good paste wax and apply a light coat, buffing when dry and then dust gently between semi-annual waxings. It’s that simple.

Fred Taylor’s “How To Be a Furniture Detective” is available for $18.95 plus $3 S&H. Also available is Fred and Gail Taylor’s DVD, “Identification of Older & Antique Furniture,” ($17 + $3 S&H) and a bound compilation of the first 60 columns of “Common Sense Antiques by Fred Taylor” ($25 + $3 S&H). For more information call 800-387-6377, fax 352-563-2916 or info@furnituredetective.com or visit www.furnituredetective.com.

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