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OILING WIND INSTRUMENTS
The idea wood should be oiled on a wind instrument might seem unusual at first but it is rooted in the understanding that wood changes size depending on many forces. Temperature, and moisture are the two most pronounced ways wood changes in size. Moisture offers the threat of cracking wooden wind instruments far more then temperature does (and the opposite is true for string instruments). The idea of oiling wood then comes down to the ability to block moisture from absorbing into that wood and keeping the wood in a permanently swollen state which aids in preventing cracks or stresses in the wood while being stored and played.
What exactly does it mean to oil wood?
This is where things become increasingly confusing, as oiling wood is not equal with all oils
A well oiled woodwind will have a bore that has a thin layer of oil exposed on the outside of the wood. This layer of oil repels water from sticking or staying in the bore of the instrument. This has many benefits in both preventing the wood from becoming swollen with moisture and also prevents and kind of rot from effecting the wood from the presence of moisture over time.
When wood is saturated with oil the grains are swollen with the oil, this expanded wood better represents the condition wood is in when growing in nature and is more geometrically stable. when wood dries out it will frequently shrink slightly and this shrinkage leads to the danger of cracks. Many woodwinds have metal keywork that is mounted into metal screws that are embedded in the wood, when the wood swells or shrinks these metal parts can make tension against the wood and cause cracks to form over time. The more stable and saturated wood is the less it will change size due to environmental conditions.
General Categories of Oils
For the use of oiling woodwinds
Polymerizing (Drying) Oil
Oils like tung and linseed oil are the principle members with oils such as poppyseed oil, safflower oil and soybean oil being slightly less common and effective members. These oils are categorized by their ability to polymerize over time as they dry out. Drying is the process where an oil evaporates out any constituents that are volatile. Oils can take from weeks, months or even years to evaporate when left on an open surface and take longer when they are absorbed into materials like wood. All drying oils contain some amount of oil that will evaporate over time, the greater the amount of the oil that polymerizes instead of evaporating the better they are at forming a hard and stable surface. Some of the oils in this category will form imperfect sticky surfaces for long periods of time before forming more stable polymerized surfaces.
Oils is this category primarily evaporate over time. These oils contain few compounds that polymerize and instead are mostly made of oils that slowly evaporate. Ideally these oils have large amounts of oils that take long periods of time to evaporate to offer the longest possible sure time. Different oils can take from weeks, months or even years to evaporate when left on an open surface and take longer when they are absorbed into materials like wood. With oils the larger the molecule size the longer the molecule will take to evaporate, also the larger the molecule size the thicker the consistency of an oil made from it has, with the longest molecule solutions being solid at room temperature (such things as saturated fats). There is a tradeoff present where an oil may be able to last longer before it evaporates but it also does not have useful working properties, because of how thick the oil is. In many of these cases secondary oils are added to make it a thin water-like solution that can soak into wood.
Synthetic oils come in a wide variety of physical properties and art typically made from silicone and from petroleum. These oils behave unlike the naturally occurring plant oils listed above. They tend to be well separated out into mono molecule solutions and can have some very exotic properties. Most of these oils fall into the evaporating category where they will evaporate over time and leave little trace of their original presence, this is unlike most plant oils because even plant oils that evaporate will leave some traces of the small amounts of oils that are drying oils. Synthetic oils are commonly used a lubrication oils for brass players and as key oil on woodwinds. Thicker varieties of these oils are also the choice oils to use for cork grease and thread oils. There is an interesting difference with lubrication oils and cork grease when it comes to woodwind communities, because the use of synthetic oils for these purposes is generally non controversial and has been widely excepted as the standard practice for well maintained instruments.
Oils commonly used to oil wind instruments
Sweet Canola oil- 1)
MCT (Coconut Oil)-
Linseed oil- Some instruments, especially replicas of historic instruments and recorders are soaked in linseed oil when manufactured. This is to allow the internal walls to have a protective polymerized layer. Though instruments with this treatment are less vulnerable to moisture many manufacturers still recommend oiling the instruments bore to maintain the best acoustic and moisture repelling properties. 2). When using linseed oil (or any other polymerizing oil) on an instrument, with the intentions of sealing the instrument there are a number of precautions that should be taken into account, specifically about altering the internal geometry of the instrument. If too thick of a later of the oil is applied and allowed to thicken, it will alter the internal geometry. Oils of this sort should be thoroughly thinned with a solvent and applied in layers to allow the oil to soak into the walls of the instrument and then any remainder in the bore or tone holes should thoroughly be removed. Using additional solvent and swabs is also a good idea to ensure no oil remains outside of the wood itself. After the first treatment the oil can be allowed to fully polymerize, taking between a week to a month and then additional layers of treatment can be applied. Once the bore hes become smooth, without additional oil altering the geometry of the instrument, the treatment is complete and should offer a great deal of resistance to moisture, comparable to paraffin wax impregnation.
Bore oil- Is a synthetic oil typically made of various mixes of mineral oils and silicone oils that have a favorable consistency for being absorbed into the pores of wood. Various manufacturers have different recipes that vary widely, and that also have different effective amounts of time that it protects the instruments. Most recipes for this kinds of oils remain proprietary to the manufacturers. Mineral oils (petroleum oils) are categorized as evaporating oils and tend to have longer evaporation times then the plant based oils. These oils also tend to have large and consistent molecule sizes and are readily available in forms that have isolated a single type of molecule for industrial use. These oils are often a mix of a large and small molecule to allow for a long evaporation time and to make an oil that is thin and water-like enough to absorb into wood.
Paraffin Wax- A unique process is used to make wooden recorders where the instruments are soaked in hot paraffin wax, often in pressure pots in order to facilitate impregnating wax into the wood and removing any air that remains 3). This process is most commonly applied to recorders made of maple wood, pear wood and fruit woods like cherry, plum, and apricot, all of these are temperate hardwoods that have many large and open pores as compared to tropical hardwoods and these woods readily allow for wax impregnation. Paraffin wax has a large molecule size compared to most other oils and under normal conditions will not absorb into woods, hence the use of heated wax in a pressure pot. This technique is less effective on woods with tighter grains such as grenadilla and rosewood. This is known to be a highly effective way to stabilize the wood and produce an instrument that will never need to be oiled at any time in its usable life. There is a drawback that if a wax impregnated instrument is left in a hot environment such as a hot car or attic it will weep paraffin out of the wood and have to be cleaned to remove it from the bore and tone holes.
Silicone oils- Silicone oil is classified by its hyper slick characteristics and long evaporation points. Silicone lubricants are common to use for oiling machinery and for oiling springs, valves and cork on wind instruments. Some synthetic based bore oil contains an amount of silicone oil. I am unaware of any bore oils that are made exclusively of silicone based oils, as many of these oils are too slick and have a tendency to migrate. Silicone oils are unlikely to be of direct use as a bore oil, but do make a good modifier to other oils to then them thinner and make them more water-like without reducing the evaporation time.
Oils Naturally Occurring in Wood
Some makers make claims that they make oils that closely match the natural oils present in the woods that instruments themselves are made of. Specifically this claim is made by the Woodwind Doctor 4) for instruments made of Grenadilla. The logic is that the best oil to use on a woodwind is one that closely matches the oils that naturally occur in the wood. This is interesting idea and brings up a relevent question, what are the oil constituents that naturally occur in woods? lets start by looking at Grenadilla.
Dalbergia melanoxylon- Commonly called Grenadilla or African Blackwood is the main wood used to make orchestral woodwinds. This wood has naturally occurring oils that are present in high amounts when harvested and which slowly leach out of the wood over time. The major oils found in the wood, leaves, and seeds are- 5)
linoleic acid (60.03%)
oleic acid (17.48%)
palmitic acid (16.72%)
Some of these oils may look familiar, as they are the same as what are found in many of the plant based oils. They are also in close ratio to those found in some of the nut oils.