Soon the summer will be upon us and it is amidst these seasonal extremes that I am asked by students: should I do something special to ensure my bamboo flutes don't crack?
There are tonnes of theories out there, but experience has taught me a couple things over the years about bamboo in the North American climate, and I thought I'd write these thoughts out in response to these questions.
I've often been asked whether I would recommend oiling bamboo flutes. Honestly, I've only done it once years ago when it was recommended to me; but, the thing is... those flutes, both mine and those of the person who recommended I oil them, all eventually saw cracks. So, what is oiling doing for the flute and why or why not to do it?
Essentially, bamboo is a wood. And as a wood, it carries within the fibre cells a certain volume of water from its days swaying in the breezes. This water wants to come to equilibrium with the humidity of the air around the flute, and when the humidity around the flute is less than that in the wood - the flute begins to dry or lose its water to the environment. When the humidity is equal or greater than that within the wood, there is either no change or a dampening of the wood.
These changes can occur gradually, and when they do, there is seldom a serious reaction as the wood gradually expands (as it dries) or contracts (as it becomes wet). The theory behind oiling wood is that a surface barrier is created that is water resistant, helping to keep water that is within the flute from escaping or vice versa.
In reality, however, my experience is that such modest protections, while effective in relatively minor humidity shifts at reducing the exchange of humidity - are in fact practically irrelevant in the kind of humidity shifts that tend to generate sudden and dangerous expansions or contractions of the wood fibres.
What types of conditions cause such shifts? ... Cars, cars and more cars.
Nothing in my recollection has been as frequently and directly related to cracks in bamboo flutes than leaving the instrument in a car. The rate at which a closed, un-airconditioned car accumulates heat and sees internal shifts in humidity is pretty hard to replicate in the normal day to day of carrying, storing or playing a bamboo flute. This environment is a death zone for bamboo, no matter what climate you are in, summer or winter. It's not simply that cars heat up a lot, it is the sheer speed at which the change occurs that seems to rapidly alter the humidity of the environment causing woods to lose or gain water faster than they're fibres are equipped to withstand.
Other student's and customers of mine have asked about lacquer and its role in protecting against cracks.
My answer to this is much the same. Lacquer can be applied to both the inside and outside surfaces of a bamboo flute. In theory, protecting the flute from absorbing water that accumulates on its surface. However, lacquer is not water proof; it is more or less water resistant. While this helps to protect particularly the interior of the flute from condensation of the breath, which forms water droplets than can soak into bare wood, it is still important to wipe away what water enters the flute frequently. Lacquer's secondary function in protecting against modest shifts in humidity, is that the hard surface it creates can act like a second skin, holding the bamboo in place and re-enforcing its bonds. It is not infallible, however, and any bamboo flute can crack regardless of what surface coating you have.
Maki bindings, which are often made of Ratan or sakura bark, are a fairly effective means of preventing cracks from either spreading or forming. Bound along areas of the body of the flute where they are not in the way of the player's fingers, these bindings apply a consistent bonding force from all sides toward the centre of the flute, effectively using force to negate any expansion of the wood body. They are quite decorative as well, and while they can cost to have applied professionally, they are one sure way to help prolong the life of your bamboo flute. Maki bindings, however, are also an organic plant mater and subject to the same expansion and contraction as bamboo when humidity shifts. You may find that a flute that looked quite sharp in Japan, finds itself with loose tangles of bindings if let to dry. The best remedy for this is either to have a professional or to attempt to re-bind the flute to the tightness you require. Ratan tightened in Japan will loosen in North America and thus if you rebind the Ratan when it has come loose here in your local climate, it is much more likely to hold firm and perform its function. This process can involve detaching the lower end of the binding delicately, and unbinding the strip until a point that it can be pulled tightly and rebound. Shaving the loose end and using a firm wood or quick drying adhesive to neatly tuck the loose end away.
Ultimately, the unique tones created in the body of a real bamboo flute are very hard to beat, which is why people are drawn to them to this day. A bamboo flute well cared for and played often, benefits from the humidity of the player's breath, a modest transmission of oil from the skin that will leave its mark on a well used flute; and, a player who plays often grows keenly aware of the nature and condition of their flutes over time. I believe this proximity and awareness is a key factor in reducing unwarranted damage to flutes from neglect. Flutes I have found cracked, were most often found that way after long periods of disuse.
And, of course, sometimes flutes just crack. Well made, more expensive flutes are usually made from bamboo that is well aged. This process allows the bamboo to dry naturally and much of the raw material will crack during drying - exposing the lengths of raw bamboo that were shaped or formed in such way that they were inherently more likely to crack and thus eliminating weak or flawed bamboo from being used in the first place. The bamboo that survives this aging process is much more resilient to cracking - but, as a natural organic fibre there are no guarantees and one may have to let go of a flute or two over time. That said, most minor cracks are perfectly repairable and seldom detract from continued use of the flute.
The moral of the story? In my books, fancy waxes and oils can help a flute owner have a sense of peace of mind, but what protection that might be gained is no replacement for an active regimen of proper care.
If you are an owner of a bamboo flute and you are concerned about your flute's longevity: play often, be aware of humidity in the environment and never leave your flutes in a car!