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Sante Fe Spruce


Timber to Timbre

The Santa Fe Spruce Company

Visualize for a moment a fine hand-made guitar, the essence of precision and elegance. Behind it, picture the raw beauty of an immense tree, cloaked in scaly bark, bristling with blue-green needles and gnarled cones. The contrast between guitar and tree is striking. And yet, the link between the two is powerful.

As a luthier’s skill and appreciation for materials grows, a deeper respect for wood inevitably develops. Often, the luthier takes a greater interest in the chain of events that provides his or her materials.Guild cover Perhaps the luthier buys a billet or a log, visits a sawmill, dries and splits a local wood, or takes a serious interest in how the wood he or she uses was prepared. The gap between tree and instrument narrows. And quite often, a lifelong romance with wood is born. It was just such a romance that carried me to the arid highlands of New Mexico to visit Santa Fe Spruce, a company specifically geared to preparing wood for musical instrument making.

My tour of Santa Fe Spruce was conducted by Tom Prisloe, president of the company. Tom, a musician (classical guitar and lute) with a background in forestry, shares the work at Santa Fe Spruce with partners Suzanne MacLean and David Bacon. As our discussion of timber and instrument making unfolded, it became clear that these three are dedicated to providing premium quality wood, prepared in a way that few other suppliers are willing or able to duplicate. The work demanded by their approach is formidable. Nevertheless, I believe their methods, successes, and problems are instructive.

As was so clearly spelled out in a GALQ editorial (Vol. 6, No. 3), there are dozens of hidden pitfalls in the wood business. In response to my question about this, Prisloe suggested that making a living as a wood supplier is probably as difficult as making a living as a luthier, especially if one is dedicated to quality. According to Prisloe, one of the most time consuming and expensive tasks he and his partners face is the ten-hour-day fieldwork necessary to locate and retrieve suitable trees. Initially, the company had hoped to purchase some of its wood from a mammoth wood wholesaler cutting timber in the area. However, when the larger company learned that Prisloe was not interested in purchasing millions of board feet, it declined to sell any wood. Actually, this has worked to the advantage of luthiers, because it forced Santa Fe Spruce to locate and cut its own timber.

Why is so much time required to locate timber? Prisloe estimates that he and Bacon cut only one tree for every thousand they look at, and this figure applies only to trees of sufficient girth (roughly 35-40 inches in diameter) to meet the needs of luthiers. In addition to size, Prisloe and Bacon look for trees that can be split into straight-faced billets. Locating such trees is more difficult than might be imagined, because hand splitting requires trees with almost perfectly straight grain. If a tree with wandering grain is purchased, cut, hauled, and split before the flaw is discovered, the entire effort must be written off.

To aid selection, Prisloe and Bacon take core samples from likely candidates. A hollow-shafted tool is bored into the tree, and a quarter-inch core, up to twenty inches in length, is extracted. However, this procedure is not entirely conclusive. The tree’s grain pattern must also be judged by subtle external indicators, and by otherTom with wood tests Prisloe and Bacon have devised. All considered, selecting suitable trees is an art rather than a science, and a sophisticated one at that. However, since a guitar’s soundboard is its most important element, meticulous timber selection is worth the effort.

Prisloe, Bacon, and MacLean cut Engelmann spruce exclusively. These coniferous trees are often 200 feet tall and 200 to 350 years old. In some cases, the company can contract to have a tree cut. In other cases, Prisloe and Bacon fell the tree themselves. In either case they face a time-consuming obstacle. Usually, only the lowest 25-30 feet of a tree is usable as instrument wood. The lower portion is free of branches, and internally it is least likely to have knots. However, the U.S. Forest Service requires removal of the entire tree, a rule designed to control the Spruce Beetle. This pest has destroyed literally hundreds of millions of board feet of timber in the Rocky Mountains. Since the beetle is harbored beneath the bark of fallen trees, they must be removed. So, the upper part of the tree, of use only for low grade lumber or firewood, must be limbed and hauled along with the more valuable lower portion.

In preparation for hauling, trees are chainsawed into 12 to 20 foot lengths and loaded onto a truck. Prisloe and Bacon do their own loading and hauling. There is an element of danger in doing so; a 40-inch by 15-foot log weighs thousands of pounds, and an accident can result in serious injury.

Back in Santa Fe the logs are chain-sawed again, this time into 22-34 inch lengths. When possible, they are stripped of bark so that their features can be studied. Prisloe and Bacon try to identify an area on each round that is least likely to produce usable wood (for example, an area with a knot or other flaw). From this point, a line is drawn through the middle of the round, dividing it in half.

Then comes the moment of truth. Wedges are set on the line and driven in with mallets and sledge hammers. As the wood parts, there is a first gwood pilelimpse inside. With it comes either delight or frustration; if the wood is flawed, all previous efforts have been wasted. As a case in point, Prisloe showed me a log that looked beautiful in every respect. However, it was riddled inside with pitch pockets. Tom estimated that he and David had 100 hours of labor in the log when the pockets were discovered. Fortunately, such flaws are rare in Engelmann spruce.

I really cannot overemphasize the importance of the next step in wood processing as it affects the guitar maker. At Santa Fe Spruce the half-rounds are entirely hand split into billets for instruments of various sizes. Hand splitting ensures that the face of each billet, and ultimately of each guitar top taken from it, is perfectly parallel to the grain of the wood. Using mallets, wedges, and froes, Prisloe and Bacon look first for larger billets suitable for cello tops. Then they split off guitar-sized pieces, followed by violin and viola billets. By using a billet length of 22-34 inches they give themselves some leeway (on all but the cello pieces) to cut off an end if it has a knot or flaw in it. In this way they maximize the yield of usable wood from each log.

In further preparation for drying, several inches of wood is split off the point (or pith side) of larger billets and discarded. The ends of each billet are coated with Sealtite 60 (Chapman Chemical Company) to close the endgrain. This product consists of paraffin dissolved in a volatile solution. When applied to the wood it penetrates about one-sixteenth of an inch and deposits a protective coating of wax. Prisloe recommends it highly.

Next, billets are cross stacked and air-dried for at least several months. Those who are familiar with drying wood in other parts of the country may wonder if this is sufficient drying time. Prisloe assured me that it is. Northern New Mexico is one of the driest areas in the U.S., with an average relative humidity of only 12%. According to Prisloe, the average moisture content of air-dried wood is about 10%. Kiln-dried wood is typically taken to about 20% moisture content. By comparison, wood air dried in Santa Fe averages about 6% moisture content—making New Mexico one of the best areas in the country for curing wood.

Billets destined for cellos, violas, violins, or arch top guitars, of course, need no sawing. These are put aside for further seasoning. Some, in fact, have been reserved for sale no sooner than five years from now. Before they are stickered for seasoning, guitar billets are sawed into matched sets. Top-quality sets are exactopstly quartersawn, but the "good" and "very good" sets deviate only minimally from vertical grain. This is another advantage of splitting the wood into wedge-shaped billets: Even tops taken from the edges of a billet are almost perfectly on the quarter. With respect to bandsaw blades, guides, and technique, Prisloe told me that Tim Olsen’s Data Sheet (#161) "says it all. "

The end result of all of the prior selection and hand splitting is guitar tops and bracing wood with virtually no run-out. Judging from some of my con-versations with friends, I would say that grain run-out has more effect on acoustics and strength than many luthiers realize. The effect on strength is actually very easy to visualize. Picture the side edge of a guitar top with the grain running lengthwise or parallel to the front. Then picture a second top with the grain running aslant, so the wood fibers are cut off as they cross the plane of the top. (Remember, we’re talking about the side grain pattern, not the verticality of end grain.) When the grain is aligned, flat (no run-out), a top will have tremendous strength. When the grain angles out, the top is weakened and may actually break when flexed. More importantly, grain run-out greatly decreases the speed at which sound is carried through a top. Since the grain fibers terminate at the surface, lengthwise sound trans-mission is diminished, and internal friction (damping) is increased.

I have long been aware of the preceding, but prior to visiting Santa Spruce, I had not had the luxury of working with split wood. I typically sawed tops from dimensional lumber, which had, in turn, been sawed straight through logs—in other words, straight through every twist and turn of grain. Because I had never worked with Engelmann spruce, I only took one top and one piece of bracing wood home after my visit. However, I soon placed an order for more. The top was a joy to work with. I was able to graduate it by hand planing, with no tearing or lift-out. Brace carving was even more amazing. Again, there was no tearing, snagging, or lift-out, and virtually no sanding necessary. The wood simply had no discernable run-out.

Engelmann spruce is still relatively unknown to many luthiers, possibly because it has traditionally been difficult to obtain. Engelmann spruce (Picea engelmanni) grows in much smaller quantities than white spruce, and is a smaller tree than sitka spruce. It is found in Central British Columbia and SW Alberta and ranges southeast to New Mexico, chiefly in the Rocky Mountains. Much of the best instrument-quality Engelmann occurs in New Mexico, where the dry climate contributes to slower growth and closer grain. However, the same conditions that slow growth also limit the number of trees large enough for guitar making. As mentioned previously, such trees are several hundred years old. They are, then, a vanishing resource. The situation is not as critical as in Europe, but some authorities estimate that that 20 years from now, Engelmann spruce will be as scarce as German spruce is presently.

I asked Prisloe if he felt there is any truth to such estimates. His repltree cuttingy was, "The fact is that large select timber, the source of high quality musical instrument wood, is on a course of de-struction. Musical instrument builders 50 to 100 years from now will only hear stories of the trees that came out of these mountains. In our search for Engelmann spruce, we are constantly running into large stands of mature select timber being marked by the Forest Service for future sale. These stands are often over ten million board feet. They will be sold to the highest bidder, which is usually a giant lumber company that will turn the wood into stud lumber for the housing industry. There are hundreds of millions of board feet tied up in this manner. We have no access to this wood. Its days are numbered, and it is out of our control."

Visually, Engelmann spruce is indistinguishable from German Spruce (Norway spruce, European spruce, Picea excelsa, or whatever else you choose to call it). Engelmann is very white, even-grained, uniform, and silky, often with pro-nounced lateral rays. It is a truly beautiful wood.

Generalizations about a particular species of wood are often relatively meaningless. For one thing, there is considerable variation of mechanical properties within each species. This is caused by variations in the proportion of early wood to late wood, closeness of grain, the area of the tree involved, the amount of lateral ray development, and so forth. Secondly, generalizations do not take into account the effects of drying and seasoning, grain verticality, presence or absence of run-out, or the overall quality of a particular top. In my opinion, none of the commonly used tone woods is absolutely superior for guitar making. Rather, each has properties that must be respected if one is to produce an exceptional instrument. Beyond this, differences in individual tops within a species dictate even further variations in dimensions and bracing.

With all of this said, I would still like to offer a few rough generalizations about Engelmann spruce. According to measurements made by Dr. Harold Snyder (1979) and Dr. Daniel Haines (1981), Engelmann spruce (ES) is typically a little lighter than both sitka spruce (SS) and German spruce (GS). According to Haines’ research, Engelmann has a sound velocity similar to both SS and GS. Haines rates Engelmann as less longitudinally stiff than SS or GS, but his rating is based on only one sample of ES, as opposed to 10 samples of GS, and 13 of SS. My experience with the select wood being cut by Santa Fe Spruce is that it has excellent stiffness—particularly when its lightness is taken into account. Compared to SS and GS, Engelmann spruce has good (i.e. minimal) low frequency damping, and superior (very minimal) high frequency damping characteristics. (Minimal damping contributes to better sustain.) By combining several indices, Haines derives a "loudness" rating for Engelmann spruce that is approximately double that of SS and GS. Thus, Engelmann spruce rates as an excellent tone wood.

Another comparison that can be made reflects the frequency spread encouraged by each species. Engelmann (at least in Haines’ single sample) has a moderate spread, whichbig logs encourages good tonal balance with an emphasis on the fundamental tone. (Note that this is before bracing and graduating.) German spruce has a medium-high frequency spread, somewhat favoring overtone production and/or treble response. Sitka spruce has a large frequency spread which encourages overtone dominance—and probably accounts for its often being the wood of choice for steel string instruments.

As can be seen above, no species of spruce is uniformly superior, although there are some differences worth noting. With this in mind, I would like to offer a few preliminary observations about how to get the most out of Engelmann spruce. These observations combine my building experience with ES to date, and my interpretation of Haines’ data, as discussed above.

The "average" ES top can be roughly 25% thicker than the "average" GS or SS top without weighing any more. This gives the maker using ES some leeway to seek an ideal top stiffness and/or graduation without adding any additional mass to the soundboard. On the basis of this, and ES’s excellent loudness rating, I would recommend making your first Engelmann top about 15 to 20% thicker than you are accustomed to making SS or GS tops. Naturally, top thickness will vary along with all the other variables of your design, and with the characteristics of a particular top. Nevertheless, this should provide a working point for graduating and tap-tuning. In other words, if you work in the range of 2.5 mm. to 3 mm. with GS, you might try a range of about 2.9 mm. to 3.5 mm. with ES, depending on what your intuition tells you. Along the same line, you may want to add about 1-2 mm. in height to the middle fan braces on a first classical guitar made with Engelmann. All of this, of course, represents an opinion, which may be peculiar to my building. Just the same, I think many makers will find it helpful.

Beyond the preceding, little other advice is needed. Engelmann works very easily, cuts cleanly, glues well, sands to a satin surface, resists splitting, and takes a beautiful finish. I think those makers who have not tried it are overlooking an exceptional tone wood. (For more information on Engelmann spruce I suggest contacting Tom Prisloe directly at Santa Fe Spruce Company, 129 Kearney Ave., Santa Fe, NM 87501)