Oiling Your Recorder
Joseph S. Wisniewski
Raw linseed oil is oil pressed from flax seeds. It is also sold as "flax oil," especially if you buy it in food grade at the local health food store. It really is a nasty tasting cooking oil, but an effective laxative. Even if you sit a pot of it on the stove and try to boil it, it will still be "raw" linseed oil. I usually soak woodwind instruments in raw linseed oil before final finishing.
Most nut oils, including raw linseed oil are very slow drying (if they dry at all) and will get "gunky" if left on the surface of the wood. Oils that don't dry are termed "non-drying oils" (suprise, surprise!) Almond oil, linseed oil, walnut oil, peanut oil, cashew oil, olive oil, grape seed oil, sunflower seed oil, rape seed oil, etc. are all non-drying oils. They are all edible to humans, so they are all edible to other forms of earth life, including bacteria and fungi. They can go rancid (stinky) and also grow mold. A little vitamin E will keep this from happening. I was suprised the other day to find a bottle of food grade almond oil (Hain brand) that looked clean, smelt clean, and even had the vitamin E already added. Again, non-drying oils should be wiped away as much as possible after oiling the bore: any oil left on the surface is going to do the gunky rancid thing (sounds like a new dance!). Their job is to replenish the little bit of the wood's own oils that get carried out of the instrument each time you wipe the bore, or leave it in a hot place, or run detergent (Dupanol, etc) through it.
Throughout most of history, musical instruments were not oiled. Then again, throughout most of history, instruments were not manufactured in Germany in the winter, placed on an airplane, taken up to near vacuum at 35,000 feet (10km), and delivered 10 hours later to the desert of California or the swamps of Florida. (OK, perhaps these examples are a bit extreme). Oiling the wood makes it harder for water to get in or out of the wood. It doesn't stop moisture gains or losses entirely, but it does provide a bit of a "vapor barrier" and reduces the odds of an instrument warping or cracking, or even raising the bore grain. These things happen when wood in some part of the instrument gets more moisture than that elsewhere, and by expanding more, creates internal stresses. At the microscopic level, stress breaks wood fibers, and loosens the bonds between fibers, so the wood gets softer, and the grain of the bore gets rougher, and the instrument gets "played out." A large stress leads to the more visible cracking and warping. Personally, I don't like cracking, warping, or raised grain.
Boiled linseed oil is raw linseed oil with some chemicals added. These chemicals are called "dryers" or "polymerizers." What they do is let the small hydrocarbon molecules in the oil join together to form long chain molecules, called "polymers," which are essentially plastics or lacquers. (Don't worry, good woods are largely lignin, another natural polymer "plastic"). Any oils that turn into natural lacquer are called "drying oils" or "self polymerizing oils" or sometimes "boiled" oils.
In the good old days (back when they would put toxic mercury in your teeth!) lead oxide was the dryer. It had to be heated into the oil (hence the term "boiled"). There are a lot of modern ways of polymerizing linseed oil. Nitric acid will do it, and can stain the wood at the same time if you add a little metal (reddish brown for iron, reddish green for copper, blue black for silver). Cyanoacrylate (CA, superglue) will polymerize linseed oil (and several other oils that are normally not considered "drying" oils, so you can make almond oil laquer with it!). Methylenemythacrylate will also work. That's enough long chemical names. Tung oil is an oil (I have no idea from what plant, but there is a botanist on this list) that is naturally self polymerizing.
Drying oils, lacquers, shellac, and common "wood sealers" do something much different from just replacing oil. They alter the bore, sometimes substantially. Something that soaks in a bit and then dries can stiffen the wood. A surface finish gives you a smoother finish. There are limits to how smooth a natural finish you can put on wood (especially maple and pear) due to the grain of the wood. Lacquer can give a maple bore the glassy smoothness of ebony or grenadilla or fine plastic). A sufficiently smooth, stiff, penetrating finish can turn any wood into the equivelant of ABS. These finishes also form a "vapor barrier" at the surface of the wood.
"Bore oil" that you buy at the local music store in little bottles is an entirely different story. It's often mineral oil or petroleum oil and has a number of interesting characteristics. First, it's biologically incompatible (except for special bacteria genetically engineered to clean up oil spills) so it does not go rancid. Second, it dries much slower, and is much more immune to natural and man-made detergents, so it stays in the bore much longer. Third, it's a very effective vapor barrier. But it's not as compatible with wood as the nut oils, and it's difficult to clean out of the bore (keeps building up in waxy layers). Personally, I avoid it. Clarinet and oboe players swear by this kind of oil, but then again, these are the same people who take Grenadilla (African Blackwood) which is absolutely beautiful with long streaks of browns, reds, and blacks, and stain it jet black (and lacquer the outside of the instrument) so it looks like plastic.
Forgot one important note: the drying oils such as boiled linseed oil or tung oil contain chemicals that make oils turn into plastic. I seem to recall reading that, if you take these oils internally (or even get them on your skin) before they dry, they can also polymerize your body's skin oils or fat, which is not a pleasant thing, sort of like being cooked from the inside. Again, that's only the boiled oils, and only before they're cured. After the finish has dried, they're harmless.