Advice for bamboo flute care

  by Angel, revised by Karl DeLong Updated Set 2019

         Avoid playing the new instrument for long periods. When a wind instrument is played, the humidity from the air in the lungs goes into the walls of the instrument. This produces a localized expansion. When the instrument dries, the walls contract.

Internal finishes slow this drying.  New flutes, although made with well-stored bamboo, should be played in times that are progressively longer That means, don't play the instrument for a long time the first day you get it. Ideally, play the instrument 15 minutes the first day, 30 the second, and then increase this time progressively.  This practice produces a kind of "fitness" in the fibers; they change, or cure, together as the humidity changes. The same is true for instruments that weren't played for long periods of time.

Dry the instrument after use. Wind instruments get some humidity from the lung's air and from saliva. It is good advice to dry the bore after a long performance. Use only fine cloths and dowels specifically designed for that purpose. Avoid introducing strange elements into the bore to avoid damaging the internal finish. 

Use of oils.  Several flutemakers recommend the use of oils (vegetable or synthetic) to preserve, and to give a better performance with, wooden or bamboo instruments. The advantages of this procedure are unclear. It is not good to oil too frequently. Excess oil, or not fine oils, may cause bad results by forming a sticky film inside the bore to which dust adheres. This definitely produces more friction with the air and therefore less sound power and richness. Some synthetic oils like silicone, or light ones like almond oil, correctly used, have shown good results for me. 

.        External care: If the instrument is lacquered, it could be cleaned with a soft cloth slightly moistened with water, or with 70% alcohol if some grease is present. Silicone products used for the plastic parts of automobiles enhance the external brightness and protect against adherence of dust.

Since I'm making bamboo instruments, customers ask me about the best way of care for them to prevent cracks and damage. I often come across statements and preconceptions about what happens with the bamboo, and with the sound, thru time. There are people who think that nothing has to be done with wood and bamboo, allowing them to "breathe", and people who suggest that they must be completely sealed (as close as possible) from the environment. 

Both thoughts have some merit, and what procedure should be followed depends on the material that we are dealing with, the maturity and seasoning, the amount of humidity, etc.

Instruments made with well-selected, stored bamboo should not substantially modify their length, diameter or wall thickness. Since initial humidity has been lost, and the instrument has reached an equilibrium with the environment, a gain or a loss of water doesn't result in large enough changes to affect the pitch of a flute.

I can say, indeed, that bamboo might crack longitudinally due to a humidity exchange with external air, or from some internal tensions in the walls. Remember that when the flutist  blows air into the instrument, this air has a different composition than that in the atmosphere, both in carbon dioxide content and in water vapor, and is almost always at a different temperature than the open air. Add to that the saliva (liquid water), which of course varies with the performer (and among instruments).  

It is normal for a wood or bamboo to have periodical changes in its degree of humidity. In last instance, the constant of the weather always changes. The problem comes when this change happens very quickly, and/or when different sectors of the wood structure have different changes. This happens in a flute, since the inner wall is in contact with lung's air and its water content and the outer wall is not.

It is important that the change of humidity happens in a more gradual way. Nitrocellulose sealant (and lacquer in some models) applied by immersion, as I do with my wind instruments, plays exactly this role.

What is more, nitrocellulose has a compatible molecular structure  with wood and bamboo. It is absolutely non toxic when dry (no fumes or solvent retention), and sustainable produced (cellulose based, not oil derivative)

Nitrocellulose is dissolved in a complex solvent, and each coat of lacquer dissolves some of the previous one. For this reason, successive coats are fully compatible between each other, making an homogeneous finishing.

I have noticed that for catching the eye (say, for commercial reasons), many makers put on only external varnish or lacquer layers. At no time have I heard about any research or justification for this procedure for either practical or acoustic reasons. 

Finishing wind instruments must be thought of in a functional way, say, that it helps for the utility, playability or enhancement of the sound of them.

The inner bore, the mouthpiece or embouchure, and the rims of toneholes are the parts more exposed to humidity, and the finishing in these areas should be done with special care. Applying varnish only to the more visible parts of the instrument is worthless, since they are certainly the lest risky zones.

Also, the finishing layer should be hard, but porous enough to allow the passage of humidity, and at the same time elastic to change with the eventual dimensional changes of the instrument, as nitrocellulose is.

Thus, the material of the instrument and the type of finishing properties should be known. In bamboo, the structure is composed of 3 basic elements:

1)      vascular bundles -known as "fibers", darker in color,

2)    the parenchyma, a clear-colored tissue that sorrounds the vascular bundles, and

3)    the skin, or epidermis, that is a semi-waterproof external covering.

Some bamboo species have amounts of wax in the skin that might be melted with a gas torch and used either to protect or to beautify the piece.

"Fibers" (vascular elements that transport the sap) give strength, whereas parenchyma gives elasticity to the structure. A very fibrous bamboo is hard, but very probably will crack since it has no elasticity for eventual contractions. In a piece of bamboo of a certain species and age, either fibers or parenchyma could be harder, or softer, or more or less elastic, compared with another bamboo. In all bamboo pieces, vascular bundles are more concentrated as one goes toward the external surface, since in the inner surface the parenchyma is dominant. 

Thus, as explained above, the inner wall of bamboo is more prone to absorb water than is its external wall. Also, the cut ends of bamboo and the walls of toneholes are more permeable than the external epidermis to liquid or gases.

Sinking a piece of bamboo with some holes into water can show this. Within hours, we will see that water penetrates from the end of bamboo and from the rims of the toneholes.

Thanks to Karl De Long and Violeta Sampedro for text revision!!

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