Deterioration of Grenadilla* Instruments

Written by Larry R. Naylor

Prologue

“Grenadilla Wood, Environmental Effects, and Organic Bore Oil” has been on my website since 2001. However, in response to comments from some readers who found that article a bit complex and involved, I offer the following revision. I hope you will find this revision more palatable. To access my 2001 article, please click here.

In this revision, I have divided my previous, single article, “Grenadilla Wood … ” into two sections: Parts 1 — 3, a discussion on wood deterioration, and Part 4, immersion rebuild using organic oils. I offer this revision to you as a dialogue I would otherwise have with you were you to visit me in my Denver shop!

As both a fellow woodwind musician and a woodwind repairman, I believe it is important to understand why our favorite instruments behave or do not behave well. With knowledge and understanding, we then are better able to maintain — if not enhance — its and our respective performance.

For the sake of discussion, I shall refer to woodwind instruments with “wooden bores” as “grenadilla instruments” regardless of whether the wood is in fact grenadilla, or cocobola, or rosewood, or some other exotic hardwood. As shown in Part 2, I shall be very deliberate regarding the term, “central heartwood.”

If you find this revision more readable and if it helps you better understand the subject matter, I would appreciate your feedback. If you find the article unsatisfying, I would welcome that feedback too. With my best regards for your continued joy in playing and enjoying instrumental music, I am …

Larry R. Naylor
NAPBIRT Master Clinician
Copyright, Larry R. Naylor, September 2009

Part 1: Does Your Instrument Have a Problem?

Eventually, many players confront a scary reality: their favorite grenadilla instruments physically deterio­rate. What can we do to avoid or even reverse deterioration? In this two-article series, I would like to reply. I draw upon three decades of empirical data and repair experience.

In this article, I hope to clarify the deterioration phenomenon. Do realize that a deteriorated instrument is usually reversible as long as no one has re-bored it. Moreover, with careful, regular maintenance, one can even avoid the possible pitfalls of deteriorating wood altogether!

“Played-Out; Blown-Out”: The Instrument Has Lost Its Voice

Many players refer to deteriorated, wooden instruments as being “played out” or “blown-out”; the instrument has “lost its voice”. This condition is particularly common in instruments that have been played extensively, but have received little preventive maintenance, or have not been played regularly and now suffer the effects of non-use. This type of deterioration does not occur in plastic or metal instruments. Let us try to describe what “blown or “played” out” means, first subjectively, then more objectively.

Discussing sound using words is problematic; I call this the “chocolate problem.” It is impossible to tell people what chocolate tastes like until they taste it for themselves! A blown-out condition may include many symptoms such as poor tuning pitch and uneven scale. By the latter, I mean that some notes pop out, while others are subdued. The instrument’s scale and registers may become out-of-tune. On clarinets, for example, the chalumeau may become sharp relative to the other registers.

Another symptom is lack of resonance. Do realize that sizable leaks, poor reeds, poor mouthpieces and poor embouchures can also lessen resonance. Presuming an instrument is in very good mechanical condi­tion, one has a good reed, etc., but it is lifeless and lacks richness, then it lacks resonance. The instrument has a “dead sound”; timbre is consistently thin and lifeless. Moreover, the sound is not rich and ringing.

Poor response usually links to a lack of resonance. When an instrument hesitates in playing interval leaps, we can refer to it as being unresponsive [i.e., dimensional changes affecting its basic acoustics have occurred]. Frequently, I meet with first-time clients who have accommodated to an unresponsive instrument; the musician must over-power its shortcomings. Eventually, the player will reach accommo­dation limits when performance problems just become overwhelming.

Typically, a deteriorating instrument degrades gradually. Over time, one begins to note small faults. Then, slowly, the faults enlarge and new faults appear. By this stage, intonation problems are now quite exaggerated. Clarinetists, Oboists, and English Hornists may note that their instruments have developed a progressive and apparently “terminal flatness”. Moreover, the instrument has become increasingly stuffy — not just on the traditionally bad notes — but eventually on whole ranges and across whole registers. For Clarinetists, the throat tones have become annoyingly and chronically stuffy. Worst of all, for the traveling musician, going from a humid to a dry climate, or vice versa, results in the instrument just not playing well at all.

Again, the condition has become chronic. All grenadilla instruments undergo a predictable change during warm-up; the wood moves ever so slightly. The tone holes change their shape ever so slightly. The pads expand ever so slightly. The keys tighten up ever so slightly. That is perfectly normal. This bears repeating: the slight changes are normal.

Deterioration: Start of the Diagnosis

Modern instrument manufacturers must account for warm-up. Moreover, manufacturers also design instru­ments to play in a “standardized, good” environment, that is, sea level, 72 degrees Fahrenheit, 40% humidity. We should address the issue of possible deterioration only after warm-up.

Presuming a deliberate and appropriate warm-up, the player should try reasonable performer tests:

• Do these undesirable conditions persist when a colleague or teacher plays your instrument?
• Do these undesirable conditions persist despite changing reeds, mouthpiece, and/or ligature?
• Do these undesirable conditions persist even after your repairman properly adjusts the instrument?
• Presuming there has been no damage to the instrument or changes to embouchure, there are two major factors left to evaluate: pads and the wood. While instinct might lead one to think “pads”, replacing pads alone may have little effect on a deteriorating instrument with diminished resonance or “dead” sound. Objective inspection is now in order.

Objective Symptoms of Deteriorated Wood

Deterioration is a measurable, negative, acoustic condition. Deterioration has very definite visual and mechanical symptoms. Those visual and mechanical symptoms, in turn, manifest themselves in acoustic degradation. Let us examine and inspect a “played out” instrument both visually and mechanically, and work towards objectively confirming the diagnosis: deteriorated wood.

Visual symptom questions to ask, include:

• Do sockets and tenons, especially on upper joints, appear bleached?
• Are socket and tenon end grains a significantly different color from the color of the body?
• Do the end grains appear significantly dryer than the body of the joint in question?
• Presuming the external surfaces have NOT been painted black, is the instrument discolored? That is, are one or more patches a significantly different tint than the rest of the instrument?
• Are there cracks through post or tone holes?
• Looking down the bore, is there evidence of raised grain in the bore?
• Is one joint warped? That is, sighting down the long axis of the joint, is it bowed? [This condition is most noticeable in upper joints of Oboes and English Horns.]

Mechanical symptom questions to ask, include:

• Are socket and bell rings loose?
• Is there a loose center joint? [Shrunken or undersized tenon shoulders and oversized sockets allow lateral movement at the center joint]
• Do keys bind?
• Do keys become too loose and noisy?
• For Oboes and English Horns: do the fine adjustments change very frequently?

Diagnosis Confirmed

Your instrument is not undergoing short-term dimensional changes associated with “warming up.” The instrument has a chronic problem, deterioration. Through visual and mechanical inspection, we have identified definite and defined symptoms. The wood has indeed deteriorated.

We now face a seemingly difficult problem. In the wild, trees adapt to their environment, be it savannah or rain forest. But, how can we adapt chopped down, cut into billets, lathed, milled and machined wooden instruments to our playing environments? Put more simply: how can we insure a relative con­stancy of “response” of our instrument to our playing environment?

Part 2: Can We Communicate Clearly About the Problem?

Now that we have objectively validated the problem, and that problem involves wood deterioration, we need common vocabulary or jargon to discuss it further. Towards that end, let us review some rudi­ments from botany.

Wood: Botany Review

Plants, like all livings things, consist of cells. While there are different kinds of plant cells, the physiology of cells is essentially the same. Cell walls surround and border each cell. In wood, cell walls consist pri­marily of long fibers called cellulose. In a matter of speaking, cellulose is the “skin” of a plant cell. Cells join, wall to wall — and there are different kinds of joined cells — each with a specific botanical func­tion. Fluids can pass among cells just under the bark by a process called osmosis.

We can conceptualize wood as a bundle of soda straws, where each straw represents end-to-end cells of cellulose. When young, these cells, called xylem, are actively involved with the respiration and growth of the tree; they carry water and minerals from the roots to the rest of the tree, and their structural func­tion is only secondary. As xylem ages, it begins to lose its transport role. Cell walls become thick and fill with lignin and hemicelluloses. This process is akin to gluing straws together, thus producing a structure of greater strength. We call the product of this lignin deposition, “wood.” Moreover, at this stage, the only function “wood” serves is providing structural strength to the tree.

There are also specialized cells called “phloem,” and still others, “cambium,” which produce new xylem and bark during a growing season. The more rapid production of xylem during the spring generates new cells that are less dense than cells produced near the end of the growing season. This accounts for, as seen in a cross section of a log, what we label as annual growth rings. Tropical hardwoods contain much more lignin within cell walls than woods from temperate climates.

Cutting Patterns and Billets

Over time, we have learned that wood from certain trees is better suited for wood­winds. Although museums are filled with woodwinds made from all manner of wood, nowadays woodwind bodies are cut predominantly from three tropical [equatorial] trees: cocobolo, rosewood, and grenadilla (the latter, mpingo, a.k.a. African blackwood, or from the French, ebony).

After crosscutting a log, it is ripped into billets of various dimensions and lengths. For soprano instru­ments, “body” billets measure roughly 2 X 2 inches, by the needed length. After quality-oriented sorting, the billets are aged or seasoned. The two-fold purpose of seasoning is to dehydrate the billets, and to allow internal stresses to balance. At some point in the seasoning process, manufacturers may bore a rough, undersized hole through the center of the billets, then let them age further. Aging time varies per manufacturer. It is quite common to season billets ten or more years. Contrarily, if one were to insuffi­ciently season the wood, the billets would be unstable in many climates. Such less than ideally seasoned billets are very prone to cracking.

Figure 2.1 below represents a cross section of an irregular log ripped into nine billets; the heavy vertical and horizontal lines represent basic saw cuts in the log; the figures are not drawn to scale. In this example, getting good, usable wood for soprano billets means this log would have to be greater than six inches in diameter. This cutting pattern produces two different grain patterns of wood; one billet of central heartwood and up to eight billets of regular heartwood, regardless of the log’s diameter.

Figure 2.2 depicts a cross-sectioned, quartered log. This log would have to be greater than four inches in diameter to produce soprano billets. Moreover, this pattern would not yield a central heartwood billet.

Figures 2.3 and 2.4 represent cross sections of the two types of cutting patterns. Note that the annular grain in the central heartwood example form concentric rings while the grain in the other billets runs “corner” to diagonal “corner.” Typically, manufacturers use central, heartwood billets when making Oboes, and English Horns, while Figure 2.4 type wood typically becomes Clarinets.

Most grenadilla billets are not central heartwood. Yet, wood used to manufacture world-class instru­ments represents the best available wood in the marketplace. The two types of billets, as in Figures 2.3 and 2.4, are simply differ­ent. They have different physical characteristics and they react differently to the environment, saliva, and age.

Now that we have a more common vocabulary, let us apply our renewed knowledge of wood to the problem of deteriorated grenadilla instruments.

Part 3: Analyzing the Problem

The manufacturer of premium grenadilla instruments must make many design decisions to produce qual­ity instruments. Fundamental decisions include the cutting patterns and duration of aging of billets. Each manufacturer has developed his own method of drying and seasoning wood, but they all have the same end in mind: to produce stable billets that are as stable as possible. Let us remember that ideal, stan­dardized environment: 72 degrees Fahrenheit etc. However, most of us play in far different environ­ments.

In much of the country, temperature and relative humidity swing wildly from summer to winter and even from day to day. Some areas present less than ideal conditions most of the year. For example, the Rocky Mountain region is usually very dry, while the Southeast is usually very humid. These differing environments often affect grenadilla instruments in negative ways, including, as a worst case, the deterioration of the wood.

There is a definite cause and effect relationship underlying blown out instruments. The major causal factors include: manufacturing processes [especially sea­soning], drying caused by local playing environment, player care & maintenance [specifically, the lack thereof], and chemistry of a player’s saliva. In turn, these effects, in order of most to least dramatic as well as most to least frequent include: cracking, binding [keys], chipping and bleached wood.

The author points out that these causes and effects are very inter-related. Thus, the subdivision below is somewhat artificial and done just for the sake of dialogue.

Stress: The Manufacturing Process & Cracking

The most obvious, also the most visible and most dramatic, example of stress relief is cracking. Cracking indicates brittle, stressed wood often caused, regretfully, by a lack of good maintenance. Let us try to understand how and why a wooden bore cracks.

All instruments are under generalized stress: the greater the stress, the less elastic is the wood. Wood is most stable when it is still alive in a tree. After harvesting, the log is cut into billets, and drying begins. After wood looses free moisture (i.e., that contained within the tubes or cellulose), the moisture content is said to be at its fiber saturation point. This moisture interacts with the wood fibers’ cellulose walls, but it does not fill the voids within the fibers. Typically, wood at its fiber saturation point has approximately 25--30% moisture. A further loss of moisture will cause the wood fibers to change shape as the wood shrinks. This shrinkage increases internal stress within the wood. The more moisture the wood loses, the greater the internal stress — if you will, the more the wood “moves.”

The relief of internal stress in wood — during and after manufacture — is a major factor accounting for how and why wood “moves.” For example, one can join and plane a hard maple board so that it is very straight and even in all directions. As a single piece, the board is under stress from shrinking during seasoning, and it is only straight because the stresses are currently in equilibrium. If one then rips, for example, one-quarter inch thick slats from this board, each slat — as well as the original board — will usually warp and twist from the relief of internal stresses that are now out of equilibrium.

As billets dry, their fibers collapse or shrink into themselves. During drying, central heartwood billets will shrink regularly towards centers, while Figure 2.4 heartwood will shrink mostly in one specific direc­tion. This drying process is only the beginning of long-term dimensional changes in the billet.

Careful seasoning maximizes billet stability. However, each billet will “remember” its own internal stress from the aging process. Aging is an attempt to reduce internal stresses; but those stresses in fact reach equilibrium rather than disappear altogether. Like that maple board cut into slats, when machining a billet into an instrument, internal stresses may re-orient within the wood, causing it to change its shape until the piece reaches a new equilibrium. For example, binding keys on a new instrument indicates that the wood is continuing to stress-relieve itself as it adapts to its current, local environment. The wood is changing dimensionally even if no one is playing the instrument.

The presence of burls and uneven grain contributes to localized stress, as will a too tight key post or register insert. A burl near a tone hole may even cause that tone hole to change shape more than other tone holes in the same piece of wood. Uneven grain, burls, overly tight posts and register inserts represent possible origins for future cracks.

Cracks occur when stresses within the wood overwhelm the wood’s elasticity at any given point. We may liken this to cracks in the foundation of a house as it settles. Moreover, any rapid change in mois­ture content and temperature will further stress the wood and increase its chances of cracking. Let us now specifically analyze the phenomenon of cracking.

Cause and Effect: Stress & Cracking

Based on my repair experience, there are four types of cracks, listed in descending order of occurrence: [1] playing a cold instrument; [2] rapid cooling of the outer surface of an otherwise warm instrument; [3] local stresses compounded by rapid temperature and moisture changes; and [4] extreme saliva damage.

The most common kind of cracking occurs when one plays a cold instrument. The sudden rush of hot, moisture-saturated air causes the wood at the bore to expand more rapidly than the wood on the out­side of the instrument. If this expansion generates pressure great enough to overcome the elasticity of the wood, the wood will crack. In central heartwood, cracks will follow a path of least resistance through postholes, tone holes, register inserts, and areas of highly localized stress. In Figure 2.4 type heartwood, cracks will occur at the edge of the grain, also following a path of least resistance.

The second most frequent cracking occurs when a warm instrument quickly cools on its outside surfaces. The wood on the outside of the instrument simply contracts faster than the inside. For example, this can occur when one opens an outside door or window near a performance area. Cracking may also occur when one puts a very warm instrument in a non-insulated case and goes outdoors on a cold day.

The third most frequent cracking involves a series of parallel cracks in one or more areas of the body. They are usually smaller than cracks caused by rapid temperature and moisture changes, and result from highly localized stress. Examples of this class of cracking occur in instruments that have been in continual use for many years — but have had little or inadequate maintenance.

Let us defer discussion of the fourth cause of cracking, saliva damage, until later in this article.

Cause and Effect: Stress & Binding Keys

Instrument dimensions will change once shipped outside of their manufacturing environments. The wood will move. This occurs very rapidly in dry environments as we have in the metro Denver area. Keys will typically bind, and joint and bell rings become loose. This contraction or expansion results from the interaction between the wood’s changing moisture content and internal stress.

Let us use premium Oboes to demonstrate how keys bind as a function of wood movement. Premium Oboes have keys fitted very precisely to hinges, pivot screws and key posts. Furthermore, hinge screws are usually fitted snugly in their respective postholes. Excess key movement is negligible; in fact, if keys were much tighter, they would not move.

Figure 3.1 represents a cross section of a premium Oboe body. Note the central, heartwood grain.

When the wood shrinks, its outside diameter gets smaller. Posts located perpendicular to the long axis will lean or move closer together as in the figure above. The associated key will no longer fit between the posts, and thus, binds. If shrinkage is great enough, the screw holes in the posts will no longer align. If the hinge screw is a snug fit in the post hole, and if the screw threads lock into the inner threaded post, the post misalignment often causes the screw to curve or flex down slightly, thus causing the key hinge tube to also bind on the warped hinge screw. Both causes for key binding typically occur on the D# and C# keys on an Oboe’s lower joint. If a key still binds after fitting the hinge tube between the posts, one knows that binding caused by post misalignment is occurring when, if you back the screw out slightly, the key then moves freely. Because springs are very light, these keys can tolerate little friction.

Cause and Effect: Brittle Wood and Chipping

In the case of brittle wood, the wood is not moving or cannot move easily. Brittle wood usually leads to chipping of tenons, sockets, tone holes, and cracks.

Wood’s lower moisture content, caused by dry climate for example, usually contributes to the brittleness of wood and, therefore, lowering its elasticity. The incidence of dimensional movement of the wood is also most noticeable during dry seasons in otherwise humid areas [e.g. winter in northern Texas, for example,]. When wood becomes more brittle, loose socket rings, and chipped tone holes increase.

Humid climates are much more instrument-friendly. However, extreme humidity can generate additional problems outside of the scope of this article. Dimensional changes and brittle wood are usually less severe in humid climates; and changes in dimensions are often so slight that they are not measurable.

Unless one damages the instrument, chipping is a manifestation of deteriorated wood. Its inelasticity relative to stress on the wood literally causes pieces to break off.

Cause and Effect: Saliva Damage and Stress

The fourth type of cracking occurs rarely, and almost exclusively in regular heartwood. This condi­tion results from extreme saliva damage or in dry areas where the swing of moisture content in the wood is extreme. Saliva damage typically is a compounding problem. That is, saliva damage usually accentuates already existent problems in the instrument’s bore.

As woodwind players, we routinely deal with saliva. Excluding physical damage, saliva is the major rea­son why reeds die. Left to their own in a relatively temperate environment, reeds will last for years However, subject that reed to acidic saliva or a foreign material like soda pop, and those substances interact chemically with cane fibers and the reed deteriorates.

In the case of the bores of grenadilla instruments, very acidic saliva usually causes grain in the bore to rise. Raised grain is especially common in dry areas, but it can be found in instruments in any climate. If strong saliva continues to erode the bore, the raised grain will eventually form deep “V” shaped recesses. Once the wood becomes thin enough from the bottom of the recess to the outside of the body, any slight stress can cause that “valley” to crack right through to the surface of the instrument.

Strong saliva will also bleach wood. Such bleaching is most noticeable, for example, on Clarinets, on the mouthpiece first, then the Barrel and top tenon of the upper joint. The bleaching may range in color from gray to white, denoting the depletion of natural oils and mineral deposits in the wood. As with brittle wood, saliva-affected wood is very inelastic. Not surprisingly, with wood in this condition, even the relatively gentle changes resulting from warming up may be enough to crack it!

Cause and Effect: Recap

Deteriorated, blown out instruments have lost resonance, compromised scale, and chronic intonation problems. The chronic degradation of pitch indicates that bore and tone hole dimensions have changed.

We have examined four major effects of deterioration: cracking, binding, brittleness, and saliva damage. In all cases, the movement of the wood [i.e. its lack of elasticity] is the cause. Stated differently, stresses on and in the wood have damaged it, or made it difficult to maintain within manufacturer-fabricated tolerances.

Must we relegate the deteriorated instrument to the back of the closet or discard it? For those inter­ested in restoring deteriorated grenadilla instruments, may I invite you to read Part 4: Immersion Resto­ration of Grenadilla and Rosewood Instruments?

Part 4: Immersion Processing of Deteriorated Grenadilla Instruments

Rewinding the Video

If the manufacturer uses the best wood available, seasons it appropriately, and manufactures it accurately, the instrument will be in its best condition when it initially leaves the factory. Perhaps, we cannot keep instruments in this pristine condition, but, with reasonable care and maintenance, we should expect that instrument to last the player’s lifetime and more. In this context, reasonable care means:

• Upon purchase, we should “set-up” the instrument for your climate and your playing environment
• We should religiously adhere to and perform appropriate, sensible care and maintenance routines
• Our repairman should render appropriate periodic, preventive maintenance
• We should develop good playing habits including preventing foreign materials from entering the bore, mitigat­ing saliva impact, playing only after warm-up, etc.

Still, even with reasonable care the wood of your instrument may eventually deteriorate due to the myriad factors of constant usage. So, you have a deteriorating or already deteriorated instrument. It is blown out. We are now left with the question: what should one do? Can it be restored?

Restoration: Goals & Objectives

While playing an instrument is a craft and art, the acoustics of why your instrument plays well involves physics and chemis­try. Doing nothing to a deteriorated instrument will only hasten its further deterioration. Repadding the instrument would be illogical, irrelevant and a waste of money. The problem is the wood. We need to solve the problem with deteriorated wood!

Restoring Wood: How to Approach the Problem

Restoration would have to bear some connection to how the wood was seasoned in the first place. When manufacturers season the wood, they set their “ideal” moisture content. And in so doing, they try to promote equilibrium in internal stress.

Saturating the deteriorated wood in water is not the answer. Applying a petroleum distillate like mineral oil is not the answer. Painting or staining the wood is not the answer. One needs to impact the wood at the molecular level to realign and re-hydrate the fibers to gain greater resiliency. The solution? Carefully staged immersion in organic oils.

Immersion Rebuild: the Process

Immersion processing can repair damaged wood in about eight weeks. Immersion processing stress-relieves wood, while generating greater fiber resilience. It begins the healing of rough, deteriorated bore, and can correct loose tenon to socket fit. After immersion processing in my shop, there is a three to four week break-in period in your environment where the instrument becomes stable in dimension and moisture balance. This stability allows the player to travel to different climate zones without suffering the typical performance problems that result from dimensional change. Typically, clients state the scales of their instruments “lock in” during this post-immersion, break-in period. In addition, most players report a noticeable increase in resonance — as well as a better scale and evenness, register to register.

Immersion processing involves preparing the wood, first by removing petroleum products from the instrument body, as well as any key oil and petroleum based cork grease. We then immerse the instrument in a tank containing a specific blend of organic oils at a controlled temperature. Depending on the condition of the wood, actual immer­sion lasts five to eight days. After immersion, we drip-dry the instrument and monitor the wood for three weeks. Once the wood is ready, we then mechanically rebuild the instrument: cleaning & refitting all keys, and installing new pads and tenon corks. Total time in shop: about five weeks.

Immersion Rebuild: Evaluation Post Facto

I usually enjoy long-term relationships with my clients, thus allowing me to receive feedback from them over the years. I also work on their instruments annually and have the opportunity to monitor instrument durability. I have found that if my clients take good care of their instruments and correctly perform periodic hand oiling, cracking is rare to non-existent. Their instruments are typically quite stable, whether in their normal environment or moving between environments.

Must we relegate that deteriorated instrument to the back of the closet or discard it? I hope I have shown you that there is a viable alternative: the immersion rebuild.

Interested in restoring that deteriorated grenadilla instrument? To determine if your instrument is a good candidate for an immersion rebuild, I invite you to contact me.

Thank you for visiting my website. I hope you found your visit useful and informative.

By Larry R. Naylor

Ed. Tait L. Solberg & N.E. Gilbert