Drowning in Oil

The original article (in German language) was published on http://www.clarissono.de/CS_Archiv/01Ertrunken.html
This is a translation by www.the-clarinets.net. Used with permission. Some paragraphs have been shortened. The document will remain in the net even if the original article may be removed. Anyway, visiting the website www.clarissono.de is definitely worthwhile (it contains English pages, too).


Contradicting Views

There are but many wood wind makers who are convinced and who will tell you that the corpus of a clarinet or oboe need from time to time to have a bath in oil. For maintenance they completely disassemble the instrument, remove all corks and pads and put the keys into a galvanic silver bath and the wooden parts into an oil bath. The duration of the oil bath varies from some days up to two weeks. Other manufacturers do disapprove - and they give reasons, why the oil bath does not make any sense (from their point of view). Yes, some even state that it will affect the sound quality of instruments in a unfavorable way. The tone will drown in oil. So - who has got it right and who is wrong?

There is a simple answer to the question, but it needs some insight into the matter. There are good points to both sides, as always. Let us first focus on the basic question:

Why do some say oiling is good?

Wood is a living material, that consists of a mixture of organic substances and minerals. Next to these the water that is bound in cells and gaps between cells is a very important factor. Before we can build any instrument parts from the wood (whatever type of wood it is) you have to let it pre-dry. This can be achieved by storing it over long periods, that is years, first in the open, then in special drying rooms or - today, much faster - in artificially climated drying chambers. Drying will reduce the water content of the wood and so the wood will shrink in volume. The idea of drying is that you want to reduce the amount of water in the wood to a degree that will later remain more or less constant, because

  • fresh wood - that is wood with too much water - would loose volume, the mechanique built (screwed) into the wood would create tensions, and the key system would not work properly or even the wood might crack.
  • dry - too dry - wood might suck up humidity from players breath in the bore and swell. This would result in blocked tensions, problems in the mechanique and - again - cracks.

This leads us to the purpose (and the only purpose) of oiling:

It shall prohibit or at least control the change in humidity in the wood. There is no doubt it makes sense to protect the wood from an excessive humidity. So what could be wrong with the oil bath, if it can achieve this goal (and everybody agrees that oil will do that)?

To answer that question we must know more about oil and its effects.

From the wood worm's perspective

Until now we have looked at the issue from an outside position. Now just do follow me into the inside of our instrument, and feel into the wood, looking at it from the wood worm's perspective. This microscopicaly small "wood worm" is feelin' good within "its" instrument (especially when you play Mozart!). And - more than anything else - it loves the vibrations, that make the instruments body swing and then its own body. But in order to make the most out of this feeling the wood worm must press its head against the wood and hold himself with his tiny feed at the walls. Only then he can swing. Otherwise the walls would just shake and the worm would become sick from being shaken from one side of his hole to the other, resulting in serious headache, even with Mozart...

An oil-drop will feel the same. Since there is not handle or hook to which it can hold itself, it can not join in with the instrument's vibrations. The drop will rather be thrown here and there - and will work like a microscopic dampener to the swinging: Each movement and friction will reduce a littel of the swinging energy. Especially the very high frequencies will suffer from that; all the little drops together will muzzle these nearly completely. In the end all the tiny drops will absorb considerable amounts of energy, and especially in the high overtone range. The result will be a much duller sound than before oiling (some will use the euphemism "darker").

In general nothing new

Some instrument makers know about these facts in detail. A well known wood wind instrument maker acts like this:

The wood will be stored in the open for eight years (at least it was like that not so long ago). Then it is put into a big vacuum-container, in wich the pressure of atmosphese ist reduced quite far. This will make all fluids that can evaporate to leave the wood, including the water (in form of steam). The chambers with wood that is dried out like that will now be filled wiht oil, and the wood will suck up the oil like a thirsty sponge.

Now the wood will rest for two more years (at least such were the standard procedures - by which I want to say that it might be different now). Not before the end of those two years the wood will be drilled and transformed into instruments.

Instruments made this way are known to show problems in the beginning, they just don't "take off" that easy, but after some years of proper treatment they will become better and better. The sound will improve and be more free. What is happening there? Shouldn't we be able to build instruments, that are perfect from day one on?

Oily details (oils ain't oils!)

Now it is time to learn a little more about oils. You have to differenciate between two larger groups of oils, that haven't got much in common except for their name. Chemically speaking they are completely different.

a) Mineralic oils

These oils are mixtures of carbon-hydrogene with 8 to 20 carbon atoms and make the most prominent part of crude oil as it is pumped out of earth and used to make petrol and gas (to end up as Diesel or gas fuel in cars or as greasing lubricants, for example). You can't eat or drink this stuff or it would kill you.

b) Organic Oil (from plants or animals)

These are, chemically speaking, glycerin ester, saturated or unsaturated carbon acids (triglyceride). You could think of these oils as fluid fat. These are the ones a wood wind instrument builder uses, and therefore I will treat them in more detail.

A triglycerid will look somewhat like this:

Bild: Triglycerid

There are three fat acids hanging at a glycerin-molecule. The fat acids could be of quite different nature. You find two types:

  1. saturated fat acids with only single junctions between the carbon (C) atoms - this is the one upper group (1)
  2. unsaturated fat acids like oil acid or linol acid with double-junctions between Cs - the lower groups on the picture (2)

The latter are called “unsaturated” because the double-junctions between C-atoms have not been saturated with H-atoms (each double-junction could and will break up into a single junction if there is an H-atom that could be bound by the molecule - this process is called saturation).

The unsaturated fat acids are what matters in the oil. Double junctions are less stable than single junctions - it comes as a surprise to those of us who did not visit chemistry classes. The process will start easily if oxygen is available. Especially this will be accelerated by light (even more under UV-light). The oxidation will produce connections between oil molecules in all three dimensions - so in the end the molecules can't move against each other any more and so become solid. This is very important for the instrument and we call the process:

The Resinification

It is very difficult to define resinifying in detail, but one could as well call it drying and sticking. All oils containing non-saturated fat acids will sooner or later go this way and become solid.

You probably know what happens if you leave a good salad oil alone in a bottle in the open for some time, don't you? There is a rest of HARZ in the neck. But some oils do this faster than others. Some do never at all, this is guaranteed. But these oils are worthless from an instrument builder's point of view (and for food purposes, too).

You will probably remember the sticky stuff in the neck of your bottle of salad oil that you left open in the sunlight, don't you? This stuff is resin. Certain oils will start to build resin faster than others. Some never ever will - guaranteed. These oils will never become smelly, and they will never dry. But they must not be used for wood wind instruments. These oils are saturated oils, like paraffine oils. They are mineral oils. Producers and companies who sell these oils will forgive me if I strongly advise you not to use these oils. They will give the wood a certain cover against humidity, but from an acoustical point of view they are bad. And then these oils will not stay in the pores of your instrument for long, but being washed away by humidity pretty soon.

Studying old books for a "how to" (that is books older than the widespread use of mineralic oils) you will usually find they mainly mention linseed oil and not much else. For hundreds of years this oil made from linseed (flax) which was always available and rather cheap was used for many wood impregnation purposes. The old books tell you that you can only use the oil when it is fresh. When it gets old, it will become smelly. This is due to the reaction of the oil; long molecule chains will break up into smaller, unsaturated fat acids, some are quite smelly. Most of us will know linseed oil in a modified form called firnis, which is used in painting. But firnis contains some metal oxides (cobalt, mangan, lead, cadmium) and these are poisonous. We rather use the native, cold pressed, fresh linseed oil, yes, just the very same stuff people pour over their salad (if they like the taste).

Except from linseed oil there is at least one oil as good as linseed oil, and that is hemp oil. But since hemp is banned in the U.S.A. (cannabis is hemp) it is slowly to take on now.

There is one more point in our search for the optimal oil: Without air (that is oxygen) there will be no effect! As you have read above, the drying process needs oxygen. That means an oilbath (even a linseed oil bath) can't be optimal - there is nearly no free oxygen in the oil. Looking at it from the wood worm's perspective the oil should make an ultrathin film on all cell walls leaving some way for oxygen to come in in order to fuel the resinifying process.

How then can I bring in the oil deep into the wood without clogging the fine pores with the resin - because at the outer openings the resinifying will start (very much like in the salad-oil bottle's neck)? The solution is a solution-aid: Citrus terpene. This is a natural, quickly evaporating (and careful: easily inflamable) solution-aid produced from natural essential plant oils. It brings the solution. Since it is an extremely thin-fluid substance it will go deep into the wood and take the oil with it. The oil will remain as a thin cover once the terpene has evaporated.

Then the pores and small chambers and channels in the wood are open again and will let the oxygen in and do its job. Oxydation and resinification will start. The oil will reach cavaties deep inside the wood and make it hard as amber (wich is the best known resin). In the bore the oil and resin will result in proper draining of water - this will prevent the expansion of the wood due to sucked in water.

Time and patience are important factors, too, since resinification takes time. It can be speeded up by adding substances that will increase the surface or assist the drying. So a suitable mixture could be: linseed oil + hempoil (all cold pressed) + citrus terpene + quartz + patience. Frequent application of small quantities of this mixture will lead to a humidity resident wood, that has never been loaded by substances that could muffle resonance. After some time this will make the instrument produce a strong tone, rich in overtones. New wood will be - in contrast - rather sensitive and must be treated with care, it will take years until perfection. New instruments should therefore be oiled frequently.

How to oil

To apply oil you use an old, non-fuzzing cotton cloth, that you dip into the oil-mix and then pull through your instrument (preferably with an aluminium flute wiper). After 15 minutes you remove the excess oil that has not been sucked up by the wood. All cloth parts that had contact with the oil must be stored in a firesafe place (like a closed steel bucket). They are not poisonous, but they might selve-inflate.

I recommend to oil the bore of a relatively new instrument about every two to three months. Later, when the instrument gets older, you do it only once a year (like when you have it for a yearly overhaul). The outer surface can be rubbed just once a year, and again, remove the excess oil 15 minutes later. This will clean away the sticky crusts from skin fat and sweat as well. But make sure the oil does not sink into the tone holes or the holes for the mechanique because it will make these stick as well.

Painting

Off course many have tried to protect instruments by painting it with moisture-resistant paint. Where only the bore was treated (usually with some two-component- or resin-paint) the results were promising, even from an acoustical point of view. But unfortunately even the best paint does not stick on for ever. The humidity will go into the wood somewhere, especially at joints and in the tone holes, undermine the painted surface and this will result in mouldering and cracking of paint. The bore will then look like being gnawed at. That is not really what we'd like to see - a mirror-like surface.

If you find paint has been applied to the outside of an instrument, then this is almost always to cover up little faults in the wood. For economical reasons it is not always possible to use fault-free wood for inexpensive instruments. This just a note for completeness...

Should you now have any questions concerning the smell of the oil mix, be assured that this will smell rather of lemons and oranges - not everybody likes that, but most of us do. This could inspire your music, too, couldn't it?

Addendum:

If you want to produce the oil mix yourself, make sure to buy only small quantities (in the bio-food-shop), since the oil will age and then resinify quickly. The mix will be good for some months, if you keep it in a dark bottle, close tight. Once opened, you should use it up quickly. If you don't know for what - it will prove good for furniture or wooden floors, too!

Martin Schöttle,
Articel for the periodic "rohrblatt" (reed),
July 1998


This is a translation by www.the-clarinets.net. Some paragraphs have been shortened. This document will remain in the net even if the original article may be removed. Anyway, visiting the website www.clarissono.de is definitely worthwhile (it contains English pages, too).




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