(At the editors' invitation, Mr. Cooper has prepared the following article based upon his very successful lecture demonstration, of the same title, presented during the initial meeting of the IDRS in August 1972 at the University of Michigan. It is our feeling that Hugh Cooper's thorough and painstaking analysis of causes, effects, and cures of hermetic leaks in bassoons represents a major contribution to the bassoon world. Such air leaks, common to all woodwinds, but present in bassoons to a disproportionate degree are a constant source of concern and trouble to the artist performer. It is our hope that Mr. Cooper's diagnostic methods and successful corrective techniques will enable individual performers, repairmen and bassoon makers to achieve a level of hermetic perfection on their instruments seldom before realized. The Society extends its sincerest appreciation to Mr. Cooper for continuing his personal dedication to the pursuit of excellence in the instrument he helped develop and we thank him again for offering to share a part of his important knowledge and techniques with us.)
In the following presentation I will attempt to establish certain criteria for determining, achieving, and maintaining the hermetic fitness and related acoustical efficiency of a bassoon.
The first criterion I will discuss is determination of the total LEAK FACTOR. The health of a bassoon (or other woodwind) is largely determined by its relative hermetic tightness. Assuming a well-designed bassoon, the "tighter" a given instrument, the better it will perform.
I challenge you to administer the test which follows on your instrument. In most instances the results will be appalling because the majority of bassoons in use are hermetic "basket cases." Many of the problems considered inherent to the bassoon (lack of projection, poor intonation, poor response, weak upper register, etc.) can be eliminated or greatly improved by reducing the high leak factor. In fact, it is only because the bassoon is such a forgiving instrument that it can be played in such a deplorable condition, an oboe, clarinet, or flute would simply refuse to play under like circumstances. If your bassoon does not meet certain minimal standards of tightness, you are laboring under a severe performance handicap.
The standards I have established for myself in bassoon servicing, include a minimum vacuum test of each joint of the instrument (wing joint, boot joint, long joint, and bell). This test is administered as follows: after stopping one end of a joint with finger, hand, cork, or cheek, I moisten any fingers to be placed over finger holes (to create a more air-tight seal) and close all finger holes and open standing keys. Next I create a vacuum by placing my mouth at the opposite end of the joint and strongly withdrawing as much air as possible from inside the joint. To determine the degree of tightness, I maintain the initial vacuum created by stopping the end of the joint with my lip, cheek, or tongue. And to test further the ability of the pads to hold their seals by suction alone, I lift my fingers away from any spring-loaded (open standing) keys. My personal standards are not met unless the joints maintain a vacuum seal for at least the following time periods.
1. WING JOINT = 1 MINUTE
2. BOOT JOINT = 30 SECONDS
3. LONG JOINT
= 30 SECONDS
4. BELL = 30 SECONDS
(Ed. Note. At this point in the lecture demonstration, Mr. Cooper performed the above minimum vacuum tests on the four separate joints of two different bassoons. One was a new instrument which he had fully serviced (his stated average time to fully service a new Puchner bassoon is 10 hours; for a new Heckel bassoon 40 or more hours). The other instrument was a new bassoon which had not been serviced Mr. Cooper was unable to even start a vacuum on the wing, boot, and long joints of the unserviced bassoon and only produced a few seconds retention on the bell. On the serviced instrument, he demonstrated that he could exceed the above minimum times by twice their length or more.)
It will be useful at this time to consider some of the effects of leaks. In general there are two broad categories of leaks which affect a bassoon. 1) MAJOR LOCALIZED LEAKS, and 2) MINOR DIFFUSED LEAKS.
Major Localized Leaks
a) If a leak at any point is large enough in relation to the bore area, the bassoon will refuse to resonate notes requiring tubing length beyond that leak. For example, a given bassoon plays well down through Low F but refuses to produce Low E or lower. The problem is Localized in one of two specific areas: the Low E pad and/or its seating or, possibly the small tenon area of the long joint. This type of leak would be exemplified by a pad falling out, a badly bent or binding mechanism, a missing or badly damaged "U"-tube or tenon cork, a major crack, a broken tenon, etc.
b) A second possible effect of a Localized leak occurs when the leak is at a node or anti-node point, causing the instrument to break uncontrollably upward to a higher vibrational mode. These leaks almost invariably occur somewhere in the wing joint or bocal area where most node anti-node points of the repeatable portion of the bassoon's scale exist. Examples would be the whisper key pad, high d, c, and a pads etc. Both types of Major Localized leaks are easy to recognize, demand immediate attention, and are relatively easy to rectify (any competent repairman can replace missing pads, straighten bent mechanisms, repair damaged tenons, etc.)
Minor Diffused Leaks
This type of leak is more difficult to detect for the instrument continues functioning at some minimal level of efficiency, therefore insidiously not demanding immediate attention. In addition the individual leaks are minor in nature and usually distributed throughout the full length of the bassoon. These small leaks occurring around pad seats, through porous pad leather, through the wood of the instrument (especially where the wood is thin or end grain is exposed) at the tenons, at the "U"-tube and surrounding metal-to-wood junctures, around posts and key guides, through "push-pin" holes in boot, and even through the "trademark" of the bassoon, all contribute in sum total to the diffused leak factor of the instrument. The effect is an increase in the acoustical damping of the bassoon.
The lower hatched line on the graph (Fig. I) represents the effect of increased damping in reducing the amplitude of the first three partials of a greatly simplified hypothetical instrument. As the damping is increased the amplitude peaks are reduced and the resonance band width broadens. The ultimate in total damping would be represented by the horizontal line on the graph; i.e., equal (zero) resonance efficiency at all frequencies. In other words, an instrument that doesn't play at all.
The physical effects of this damping are as follows:
a) The resonance efficiency of the instrument decreases as the leak factor increases.
b ) Higher frequencies are affected proportionately more than lower frequencies.
c) The resonance band width increases in proportion to the leak factor, offering a somewhat more flexible frequency response (pitch). On the surface this seems an advantage.
d) The general pitch level becomes lower as the damping is increased. (The low pitch level of most new Heckel bassoons is primarily caused by an extremely high diffused leak factor due to very porous wood as well as the other more usual sources of diffused leaks. When these conditions are rectified, the pitch center rises to normal.)
e) The leak factor sometimes acts as a band pass filter, thus eliminating isolated frequencies or frequency areas entirely.
The subjective effects which take place as the leak factor (damping) increases are as follows:
a) The bassoon sounds progressively "darker" with proportionate loss of projection.
b) Resistance increases, requiring more effort to play.
c) Problems of attack, stability, and projection are encountered in producing the higher register.
d) Response is difficult in the low register.
e) The pitch center is lowered (an advantage up to a point).
f) There is increased pitch flexibility (however, this advantage is largely sacrificed by the performer having to use stronger, less flexible reeds in an attempt to regain lost projection and high register response.)
Performers accustomed to playing on highly damped bassoons have adapted their whole approach to an inefficient resonator. They will not always be immediately able or willing to accept the differences inherent in an efficient, well-adjusted bassoon. However once acclimated, the same individuals will never again wish to play a stuffy, unresponsive, leaky instrument. Such fortunate individuals will have discovered that the utilization of high damping in an instrumental performance situation should depend on controllable, intentional damping contributed by the artist-performer at the embouchure/reed coupling. Under no circumstances should high damping reflect a built-in limitation of the equipment.
The responsibility for hermetic tightness should lie with the manufacturer, distributor, or repairman. When any of the above try to convince you that hermetic tightness is unimportant (After all, the bassoon plays, doesn't it?), there are five possible reasons why:
(1). He doesn't know any better.
(2). He doesn't wish to spend the necessary time and effort.
(3). He knows he doesn't have sufficient knowledge or skill to correct the faults even if he did spend the time and effort.
(4). He knows you are unwilling to pay for the extra time and effort; or
(5). He knows that the specific bassoon is a poorly designed bad bassoon which must be excessively damped to be playable. Conditions will never improve unless you, the consumer who now should know better, refuse to accept inadequately serviced bassoons from any source.
The majority of top American bassoonists (woodwinds) of the past three generations have had the high standards of W. Hans Moennig as their criteria for excellence. WHAT ARE YOURS?
I offer the following causes of leaks, their effects and certain appropriate corrective techniques in hope that such information will be of aid to you in achieving similar high standards.
I. Padseats (See Fig. 2, A, B, C, and D)
A. Types of problems include:
1. Chips in the wood (See Fig. 2A)
2. Tool chatter marks and/or raised, corrugated graining of the wood (See Fig. 2A)
3. Pad seats not in a plane (undulations, especially on the large angled tone holes like low F. G. A8) (See Fig. 2B)
4. Porosity of wood at the edge of the pad seat (See Fig. 2C)
5. Flat pad seats (poor design) (See Fig. 2D)
B. Methods for correcting the above conditions include:
1. Fill deep chips in the wood with "Matchwood," a plastic type filler; "Magic Wood," similar to "Plastic Wood" but better for this purpose; "Furniture Fix," an epoxy filler; or any other high quality wood filler available. However, if time is of the essence, stick shellac may be "melted in" to fill the chip. After the filler is hard, sand as in #2 below.
2. Sand the shallow chips, chatter marks, corrugations and undulations smooth with folded sandpaper, three thickness thick and 1/4 inch wide, held between thumb and index finger while rotated around circumference of the pad seat (at first, 180, then subsequently finer grades to 600). Make sure that the original semiconical slope of the pad seat is maintained - Remember, from a performance standpoint, it is far more important that the pad seats have a beautifully smooth surface than does the exterior surface of the instrument. Take time to examine your bassoon to determine the condition of its "valve seats."
3. Laboriously recarve flat pad seats to the correct contour. I contour the seat with a triangular scraper (burring knife) and then sand smooth as in # 2 above. Another version of this problem is the recent "improvement?" made by one famous maker who now routs out a superimposed circular depression on the low A and F tone hole pad seats, thus making it totally impossible to stop leaks in these areas without dropping the whole level of the pad seat to eliminate this depression. What price progress?
4. Correct porosity of the wood with (preferably) - raw linseed oil, oil containing a drying agent such as "Birchwood Casey" gunstock finish or, if you lack drying time, use very thin lacquer. Any of the above should be applied to all exposed raw wood areas suspected of porosity. Although I prefer the raw linseed method, it is time consuming, taking several days at best and several weeks at worst. The raw oil should be puddled on exposed pad seats and in tone holes daily until the wood refuses to absorb any more oil. The excess oil is then wiped off and the instrument is allowed to air dry for several days before the keys are replaced. (Some people prefer complete immersion of the bassoon joints in oil rather than the puddling method. I personally feel such an approach may cause bore distortion.)
II. Pads (See Fig. 3A and B)
A. Types of problems include:
1. Porosity of the leather itself (See Fig. 3A). Arrows indicate directional path of leaks. (See Fig. 3B) Hatched area indicates the porous surface area of pad which contributes to the leak factor.
2. Poor seating of the pad. (Ed Note: Mr. Cooper at this point discussed the various ways of inserting pads in their cups and how to "tease" the pad at an four quadrant testing points with a 1/8 to 1/4 inch strip of tissue paper or gold-beater's skin; but he emphasized that this "paper" test is only valid after the pad seat is completely smooth and free of chips, corrugations and other imperfections.)
3. Torn, cut, or water-hardened pads.
4. Dirt or debris on pads and pad seats.
5. Spring tension too light, allowing pad to leak under influence of positive pressure or sympathetic vibration.
B. Methods for correcting the above conditions are:
1 . Paraffin the pad centers (See Fig. 3B) The hatched area indicates the portion of pad surface to be coated with paraffin wax. (Caution: do not paraffin beyond pad's contact point with pad seat and be sure to cover completely the center stitch holes.) Paraffining is accomplished by flowing a thin coat of melted wax on the pad surface with a small heated spatula (A small screw driver with rounded corners works fine), coming to within 1/ 2 millimeter or less of the pad seat indentation. Practice on large pads first!
2. Seat the pads very carefully and accurately, using all the common techniques for matching cup and pad to the seat, such as tapping with a hammer, key bending, pad slick (shifting the floating pad in its heated cup), and using shims if necessary to build up low areas, remembering always that when seated, the pad surface must be absolutely parallel to the plane of the pad seat.
3. Replace torn, cut, or water hardened pads with high quality, kid leather, felt or flannel filled pads. The best source for pads is the particular maker that produced your bassoon. Write and order direct. They will be happy to supply specific sized individual pads or complete sets. (While you're at it, I suggest you order a few pivot screws and key axle rods, threaded and nonthreaded. Ask for long axles as they can always be cut down to length and reslotted. Carry some of these spares in your case at all times for such items are hard to find in an emergency.)
The replacement pad, except for the little finger F # pad or smaller, is first stitched in the center to avoid an excess bellying of the pad center after seating and to eliminate the "leather lag" caused by the pad leather clinging to the pad seat of the instrument during performance. (Note that the stitches in the low G key and boot Bb pads must be placed off center because of multiple tone hole drillings.)
After stitching, the replacement pad is floated into the pad cup with molten brown or white stick pad shellac, leveled with a pad slick and allowed to cool. The key is then replaced on the bassoon and the pad is teased out as discussed in A2 above. If correction is needed, apply the techniques discussed in B2 above, until the pad teases well in all quadrants but a little stronger at the point furthest from the key axle. Then, and only then, press firmly down on top of the key cup (with small wooden tool handle) to seat the pad. Tease again - now checking for equal contact in all quadrants, and, if necessary, repeat any of the above techniques until the seating is perfect. If time permits, cork the key firmly closed for several hours before attempting to paraffin the center. It is important to note that the seating is done while the key is cold or at most warm - never while the shellac is molten hot. The small leather high d, c, and a pads on the wing joint may be paraffined -- (a delicate job); however, it is better to replace these sensitive speaker key pads with carefully seated, high quality, non-porous cork pads.
5. Loose dirt or debris on pads and pad seats should be removed by brushing with a soft bristle brush. Imbedded particles must be carefully lifted free with your fingernail. Preventive maintenance should include a weekly brushing of pads, seats, and space under keys with a small 1/2" paint brush. Even one piece of reed- shaving caught under a pad can cause a substantial leak!
6. Leaks caused by weak spring tension cannot be detected by the vacuum test but must be located using a positive pressure test. To test, proceed as with the vacuum test, only blow into the joint with a slight positive pressure. A pressure leak will become audible when the key "blows up" while acting as a pressure relief valve. The motion of the offending key is more often than not visible. Obviously one could always blow hard enough to overcome normal spring tension but if a leak occurs under any reasonable level of pressure, the spring must be strengthened until the leak is eliminated. Spring tension on normally closed keys must be strong enough to ensure a proper seal under playing conditions, yet be light enough not to hamper facility.
III. Bottom of the boot joint [wood body, metal ferrule, gasket, and "U"-tube - see Fig. 4 (boot nomenclature) and Fig. 5A, B. and C.] This area should be periodically tested for leaks by immersing the boot in water to a level slightly above the juncture of metal ferrule and wood, with the "U"-tube in place and the protective cap removed (see Fig. 5 "water level"). Cover all open keys and finger holes then blow into the boot joint with one side of open bore covered or plugged (chin works fine). Any leaks present will reveal their location as bubbles being emitted from the leak source.
A. The least common leak is caused by a defective "U"-tube solder joint (see Fig. 5A). If such a leak is major, it must be resoldered; if minor, it can usually be corrected from the outside of the "U"-tube with epoxy.
B. Defective cork or rubber gasket. (Cork is preferable as rubber gaskets squeeze in and obstruct the bore.) (See Fig. 5B) This gasket is often damaged during periodic removal of the "U"-tube. If the gasket is cracked or torn, it must be replaced. However, minor leaks can be stopped by the use of cork grease or vaseline on the contact surfaces. The gasket should only be cemented to the "U"-tube, never to the body of the instrument. Replacement gaskets should match the old one in thickness, unless you deliberately wish to change length of bore to affect pitch. Remember any change in gasket thickness will have a double effect on length of bore.
C. A major area for leaks is between the metal ferrule and wooden body of the bassoon (See Fig. 5C). Under normal circumstances this type of leak may be corrected by the use of melted paraffin and heat through liquid flow and capillary action. A small propane torch is used to heat carefully the metal ferrule, after a liberal application of melted paraffin wax to the metal/wood contact areas. The boot is slowly rotated as the torch flame (on low) is directed at the lower outer edge of the metal ferrule. Keep one of your index fingers in contact with the ferrule to test for excessive heat. When the temperature of the metal exceeds the melting point of paraffin, capillary action will cause the paraffin to flow into the minutest of openings and stop all air leaks in this area. Note that the -"U"-tube and its gasket must first be removed from the boot joint before heat is applied to the metal ferrule and, upon completion of the procedure, all excess paraffin must be removed from the outside surface and inside bore of the bassoon. In extreme cases involving wood rot (usually caused by chronic untreated leaks in this area) the metal fittings must be removed, the wood repaired and some substantial filler used.
IV. Porosity of the wood--bassoon body (See Fig. 6A, B. C and D)
A. Types of problems include:
1. End grain of the tenor joint (See Fig. 6A)
2. Around metal posts (also key and spring guides). (See Fig. 6B)
3. Bocal receiver (socket) (See Fig. 6C)
4. Trademark stampings (See Fig. 6D)
B. Methods for correcting the above include:
1. Leaks through end grain of tenor (or other) joints may be corrected by:
a. Flowing melted paraffin into exposed end grain with heated metal spatula.
b. Painting exposed end grain with several coats of thin lacquer such as thinned clear fingernail polish.
c. Prolonged immersion in linseed oil until porosity of wood is eliminated.2. Leaks around posts can be stopped by three methods.
a. Flow a bead of melted paraffin wax around the base of each offending post . Afterwards carefully heat post until paraffin again melts and capillary action causes wax to flow into space between post metal and wood of body. (This is my preferred method).
b. A second solution is to flow a coat of very thin lacquer around the base of each offending post. Add additional coats until the leak is eliminated. This works well but unlike the paraffin method leaves visual evidence of work done.
c. Prolonged immersion of joint in raw linseed oil until porosity of wood is eliminated.3. Bocal receiver leaks can usually be eliminated by heating the metal ferrule at top of wing joint to a temperature above the melting point of paraffin. After heating, dip the top of the wing joint into a small jar of melted paraffin somewhat beyond the depth of the metal ferrule. Repeat this process several times and then wipe the excess wax from the bassoon, being especially careful to remove all vestiges from inside the bore, receiver, and high d and c tone holes.
If the receiver is loose and turning in its wooden socket paraffin alone will not solve the problem. Two corrective approaches may be used.
a. If the receiver can be removed from bassoon, (on some make bassoons, the top whisper key post must be unscrewed first), epoxy it back in place making sure that the excess epoxy is removed from bore and receiver before setting.
b. If the receiver cannot be removed from its socket, yet still moves slightly or turns, a set screw may be placed vertically in the top of the wing joint which will prohibit the receiver from turning. After immobilizing the receiver, treatment with paraffin as outlined above will usually be successful.
4. Trademark stampings or other breaks in the skin of finish are sources of leaks. Again the three methods may be used.
a. Working melted paraffin into the wood with hot spatula.
b. Painting suspected area with several coats of thin lacquer.
c. Prolonged immersion in oil.
It should be pointed out that the above type leaks can only be specifically located by a positive pressure test while the joint is immersed in water. Rather than immersing each joint in water, I assume that these areas do leak and routinely treat them during normal servicing.
Now that we have located the leaks and corrected them, it is important to maintain the bassoon in its excellent condition. One major threat to the continued health of the instrument is water damage caused by incorrect handling. The following few basic rules will help to minimize the water problem.
1. To avoid water damage, NEVER allow the bell of the assembled bassoon to dip level with or lower than the bottom of the boot joint. Such a position would allow any water collected in the "U"-tube area to flow down the unlined side of the boot joint, thus causing serious water damage and distortion to the bore, tone holes, pads and pad seats in this area. For the same reason, until you have poured and swabbed water from the boot joint, do not lay it temporarily in the case or on any other surface without propping the top end of joint to a higher level than the bottom.
2. While resting during performance, rehearsal, or practice, rotate the bassoon in your hands so that the bocal tip points toward your left shoulder and always continue to keep the level of the bell well above the boot. This procedure, coupled with #3 below, avoids 90% of the water-in-finger-hole problem. Water can't run uphill!
3. Establish a water condensation pattern in the wing and boot joints' lined bore which avoids all tone holes. (Especially important with a new bassoon).
a. Warm up the instrument with the bocal turned, to the right in the wing joint, at an unnatural angle. (Far enough so whisper pad will no longer cover vent hole). When the instrument is warmed up and a moisture pattern established, turn the bocal to a normal position.
b. Adopt a normal playing angle which allows the water pattern to avoid tone and finger holes. That is, the bocal should be turned in the receiver as far as practicable to the right, so that the far edge of pad just covers the whisper vent.
c. To break the surface tension, run a drop of water, before assembly, through the lined bores of wing and boot joints, steering it down the inner curve so as to avoid all tone holes.
4. ALWAYS pour accumulated water out the lined small side of the boot joint (see #1 above).
5. Swab the bassoon dry after each use.
a. Use only a pull-through swab-longer than the joint and made of lint-free material (such as laundered diaper cloth) for the wing joint.
b. The same swab wrapped around a wooden, plastic or smooth aluminum rod can be used for swabbing the small side of the boot joint .
c. Large side of boot, long joint, and bell should never have to be swabbed (except for periodic dusting) if the bassoon has been handled properly.
d. NEVER use the fuzzy wire-centered swabs supplied with new bassoons. They do not dry the bore - the wire can scratch the bore - and they leave deposits of wool lint in the bore and tone holes.
e. Make sure all water is out of the finger and tone holes before putting the bassoon in case. (Blow out and dry carefully with pipe cleaner).
Compliance with all the above procedures will help keep your bassoon in top working order and greatly reduce the need for periodic service and repair. Most pads on my bassoon are original equipment, even after forty years of use.
In conclusion, I hope that this discussion will enable concerned bassoonists to achieve and maintain a higher standard of excellence in their instruments. Each leak ferreted out and eliminated will bring about a related improvement in the bassoon's acoustical efficiency; however, the most dramatic change will be accomplished by the first fifteen seconds gained in vacuum test capability. Thereafter, although the result of each subsequent gain is very real, it is not as noticeable as the initial change. For example, the qualitative difference between a bassoon having close to a zero vacuum wing joint (normal on most bassoons in use) and the same instrument after it has been improved to fifteen seconds is phenomenal, while the differential between a one-minute versus a one and one-quarter minute vacuum test capability is far less apparent. My point is, that any reader, possessing even minimal mechanical skills, can, by applying the techniques previously described, improve his or her instrument to such a basic extent. With a greater application of effort and skill it is possible to achieve the higher standards that I feel are necessary for full realization of an instrument's capabilities. Until such time as these standards are met, anything else done in way of "improvement" to the instrument, i.e. tone hole modification, pad height, reed adaption, etc. - important as they admittedly are - is merely a random symptomatic treatment of an ailing instrument whose full capabilities will continue to remain hidden by the acoustical limitations of hermetic ill health.
Ed. Note: Mr. Cooper has promised future articles on mechanical adjustment and the effects of tone hole modifications. It might also be of interest to some of our readers to know that Mr. Cooper offers a seminar in bassoon voicing and repair each year during the regular eight-week University of Michigan School of Music Summer Session July and August). Individuals wishing more information regarding the specifies of admission should contact Mr. Cooper or Mr. John Smith, Admission Officer of the University of Michigan School of Music, Ann Arbor, Michigan.