Personal Note: Edmund Nielsen, founder of Edmund Nielsen Woodwinds, Inc. and late husband of Dorothy Nielsen, published this article on instrument cracking in To the World’s Oboists, in August of 1975. We feel that the information provided in this insightful article is as valid today as ever and am reprinting it here for your enjoyment.

Cracks in woodwind instruments are caused by neglect. A strong statement? A statement scarcely calculated to win friends? True. But it is based on over 30 years of repair experience.

We all worry about those cracks that develop in the upper half of the upper sections of oboes, English horns and clarinets. Over the years, I have repeatedly analyzed this problem and have come to the conclusion that this cracking is the result of allowing the inner fibers of the wood at the bore to expand suddenly and excessively while the outer wood surfaces are in a contracted condition. That we are dealing with an extremely powerful force is demonstrated by the common examples that we can see around us. Who has not seen a sidewalk or a street that has cracked as a result of tree roots that have expanded? Each individual root fiber may be very minute, but when it expands and adds to the stress of the fiber next to it the resultant force is enough to cause the pavement to crack. An even more common example is the way that many wooden doors and windows stick in damp humid weather, but move freely when drier weather returns.

Moisture, Temperature, and Cracks

Most cracked instruments come from areas that have a relatively low humidity. In homes with central heating, the indoor humidity in winter is generally excessively low, possibly 25% or less. If an instrument has not been played for several days, the low humidity will cause the wood - both inside and outside - to dry out and contract. This accounts for some of the major problems experienced with new instruments during their first winter. As the wood contracts, the posts draw closer together, resulting in keys that become too tight, bind or stick. The wood around the threads of the posts also shrinks, causing loose posts. Rings that have been tight around the wood may become loose and even fall off. Some of these problems are inevitable during the first winter, but they all serve to illustrate my point that, because of variations in moisture and temperature, the wood of an instrument is far from stable.

If you play an instrument that has been allowed to dry and contract, moisture will accumulate inside the upper part of the upper section. A combined result of the condensation of moist air coming from the mouth and saliva, this moisture will quickly become absorbed into the dry, thirsty inner surfaces of the bore. As each wood fiber expands, it begins to exert force against those outer surfaces that remain excessively dry and contracted. If these conditions are allowed to exist for a long enough period of time, some part of the outer surface is bound to give way and a crack will result. The outer surfaces of the wood are weakest where tone holes or posts have been drilled, and this is usually where such cracks appear. They usually follow parallel to the-natural graining of the wood; close examination will reveal that the crack is seldom in the coarse grain itself, but more likely very near it.

Instruments rarely crack under excessively humid atmospheric conditions, because the same degree of humidity exists both outside and inside the instrument. Under these conditions, the already moist wood will not absorb much additional moisture, so the inner surface will not expand excessively in relation to the outer surface. This explains why we seldom see new cracks develop in the summer, when instruments are stored, or when they are used in climates that are normally warm and moist.

I do not subscribe to the fatalistic view held by some that a new instrument is bound to crack. It will crack only under the conditions of excessive expansion and contraction that I have outlined. Nor do I believe that the age of the wood itself is responsible. I have seen very old un-cracked instruments stored for a long period of time and then put back into use. Only then did they crack! Obviously, the dry bore was allowed to expand too much due to excessive moisture absorption.

It may be true that a relatively high percentage of new instruments do crack, but identical conditions exist with the wood of new instruments and old instruments that have been out of use. In both instances, the wood is dry and contracted and then subjected to an excessive amount of moisture, which is all too often allowed to accumulate in the bore.

Cracks can seldom be attributed to "natural flaws" in the wood. From the experience I have gained in building my own oboe, I know the stresses and strains that a piece of grenadilla wood is subjected to under normal construction during boring, polishing, drilling, etc. Any natural flaws in the wood are bound to show up during these procedures. It is certainly far more economical for a reputable oboe maker to discard the wood at the first sign of a flaw, rather than to continue laboring for so many hours - only to end up with a flawed product.

Preventing Cracks

Unfortunately, some very common crack preventative measures are not very effective. Case humidifiers, for example can cause rusted springs and screws and warped pads if used excessively. But the worst offenders (in my opinion) are those "in the bore" devices that keep the bore moist and expanded.
Swabbing out the upper section is, of course, very important. Perhaps the most common method is the use of turkey feathers. This has been the accepted procedure for many generations. I myself used feathers for many years, since they were universally accepted and nothing else was available. That is not true today. One must bear in mind that feathers were designed by nature to repel water, not to absorb it. If this was not the case, a bird could not fly in rainy weather! The use of a feather serves little purpose other than to spread the excessive moisture evenly around the bore - which still permits the moisture to be absorbed into the wood. On the other hand, the new type of cloth swab (if used properly) will thoroughly remove all moisture before it can be absorbed. As an oboe player, I must admit that the use of a feather is faster and certainly more convenient during the pressures of a performance. It is extremely important, however, to remove the accumulated moisture completely with a cloth swab as soon and as often as time permits.

The new type of cloth swab to which I am referring consists of a triangular piece of cotton cloth to which a weighted string is attached. This will just fit into the bore and when drawn up snug in the upper section, it will still leave ample cloth at the bottom to permit the swab to be pulled out. Never attempt to pull this type of swab all the way through the upper section, as the wide end of the cloth will not fit through. Merely draw the cloth through until it is snug and then remove it from the bottom.

I have found that the Larilee oboe swab and the Linton English horn swabs are the most effective and I enclose one of these swabs with every instrument I sell, new or used regardless of make . . . along with a lecture stating my views on crack prevention. The relatively low incidence of cracking in the instruments I have sold since I first launched my "anti-turkey-feather" campaign has further served to strengthen my convictions.

Many people recommend the periodic oiling of the wood with bore oil. I hesitate to recommend oiling because I have seen so many cases of excessive oiling which can cause an instrument to develop a dull and loggy type of tone; it can also cause pads to deteriorate I have even seen a few cracks in oboes that I believe were caused by over-oiling the bore. The wood of an instrument can expand and crack as a result of excessive absorption of any kind of moisture, including oil. Bore oiling can be done - but very carefully and only if a very light film of oil is left on the wood. Great care must be taken to avoid getting any bore oil on the pads or on the mechanisms. Any excessive oil not absorbed by the wood within a reasonable amount of time should be carefully removed.

Need I remind you of the dangers of blowing warm, humid 98-degree breath into a very cold instrument? Every so often we find an instrument that has cracked as a direct result of being played too soon after being outdoors in very cold weather. A wood instrument brought in from the cold should be allowed to warm up to room temperature before it is played. This can present quite a serious problem to woodwind students who have band first period in the morning and must very quickly warm up cold instruments.

Thus far we have been describing cracks normally found in the upper half of the top sections of oboes, English horns and clarinets, clarinet barrels and the wooden head-joints of flutes and piccolos that are not metal lined. We have not been referring to the cracks often seen at the female tenon at the top of the middle section and at the top of the bell on oboes and English horns. Here we do not have a moisture problem just the normal contracting or aging of the wood to contend with. The wood is very thin at these points and will split after shrinking down against the metal socket liner, which will not shrink. These cracks are not serious, and only minor repair is necessary.

What to Do When Cracks Occur

I have made it a practice to discuss my views on cracking and prevention of cracks with all purchasers of woodwind instruments. In spite of this, a small percentage of instruments do crack and must be returned for repair. Initially, a crack might appear "large enough to drive a truck through," but by the time the instrument arrives at a repair shop several days later, it may be extremely difficult (if not impossible) to find the crack; the moisture in the wood has by then equalized and the expanded bore has contracted, making the crack virtually invisible. A crack should be marked very carefully and clearly with a pencil while it is easily visible, with perpendicular lines to mark the top and bottom. The instrument should not be played until the crack has been repaired. Surface cracks can be pinned and further trouble to the player eliminated, but if neglected and if expansion and contraction are allowed to continue without the benefit of pins, the crack can eventually go all the way through to the bore. Once this has occurred, it is sometimes considered advisable to have the wood of the upper joint replaced.

As a professional repairman, I have fixed many hundreds of cracked instruments. But this has been one of the most disheartening aspects of a 30-year career. Perhaps it is because I am also a performing oboist that I hate to see an otherwise beautiful instrument marred by a crack that might very easily have been avoided!