Wood Drying & Storage
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Woods used in guitar building are costly and in many cases, more delicate than the woods used for general construction. Because the components are often thinly cut and because many are high in density or may have unusual figured grain patterns, guitar woods require special care to keep them free from cracks and warpage and to ensure the longevity of the completed instrument.
People often wonder about the wood storage conditions here at LMI’s Northern California facility. The particular climate-type in our region is very unique and is more typical of the Mediterranean than it is of the United States in general; in fact it is a climate-type only found here and in the areas around the Northern Mediterranean, in Central Chile and in South Africa. We enjoy mild temperatures and humidity (year round average under 60%) and are normally immune from the dry air common in the winter months around most of the United States (and in the mountains and deserts) and suffer none of the high humidity common in most places during the summer. These conditions make it perfect for growing the grapes used in the world’s finest wines (our main local industry) and also happen to be excellent for storing tonewoods!
A business like LMI’s could not easily exist located in a region with harsher weather patterns. At LMI we are able to receive, process and store our woods without imposing an artificial atmospheric environment. The wood seasoning process actually benefits from the natural, but not extreme, fluctuations in temperature and humidity it encounters in a warehouse of this type.
This is not to say that we sell seasoned wood! In the violin making world, there are a handful of suppliers who date each particular piece of wood they sell and then store it for years and years in very specific conditions. The cost of the wood is commensurate with the length of time it is seasoned and is exponentially greater than even our most expensive woods! Instead of following this model, we maintain an atmosphere that benefits a variety of species, all being stored in the same warehouse in various states of production (lumber, billets, sawn parts, veneers, some wet some dry). On average, woods will spend around 6 months in the warehouse before they are offered for sale. In order to get wood ready for storage (and ready to sell), we use our slow drying dehumidifier and take the moisture content down to around 8 to 10% The length of time this process takes is determined by the initial moisture content of the wood and by the density of the wood. Pre-sawn Rosewood backs, for example, can take about 2 weeks and thicker Ebony parts can take 4 to 8 weeks in the dehumidifier.
In theory, and when the situation necessitates, you can build with LMI woods as soon as you receive your package. Still, whenever possible, it is best if you allow the wood you receive to acclimate to your shop for awhile. Even if the climate in your area were identical to ours, you should still account for the different climates the wood has traveled through to get to you. If your shop is humidity controlled, then a week is usually long enough, though many choose to wait several weeks –or even longer. It is not uncommon for burgeoning professional luthiers to invest in a lifetime’s supply of staples like Ebony fingerboards or Rosewood backs and sides early in their career so that the wood can become more stable over time. Another good reason for doing this is that we offer generous quantity discounts for those who buy wood in bulk (just call or write and ask for the LMI sales manager about this).
When you receive your wood, you want to store it so that it is not exposed to excess humidity and extreme fluctuations in temperature. In most climates a dehumidifier is a must during the summer months and a humidifier is used during the winter, or whenever intense heating is used (woods stoves especially) or moisture-robbing air conditioner units.
Store the wood stacked on stickers. Stickers are long, cleanly cut square sticks of wood that are light in color (dark wood may stain your tonewood) and free of sap. Many quality plywoods are fine. The ones we use are about 3/4" x 3/4" but the dimensions are not critical, so long as they are common to all the stickers you use. The idea is to make sure that air can circulate around both sides of the wood. Sticker the wood with at least 4 stickers, with stickers placed beneath the lowest pieces and the base (which ideally is made of plywood). Make sure the wood extends from the end of the wood being stickered or is no less than ½” from the ends. Stickers should be placed directly over one another in order to avoid distortion. To keep things flat, add weight to the top level or bind the stack tight with rubber tubing.
Stack the wood in a closet or a special cabinet. The storage area should be closed but not air-tight, so that air can circulate freely. Put a low wattage light bulb inside and keep the light on. The bulb will increase the temperature in the enclosure slightly so that moisture is encouraged to slowly escape from the wood.
In the event that you want to work with a piece of wood that is a little warped, paint some water over the concave side of the warped piece and sticker it for a least a week.
Woods should be stored with surfaces clear of sealant or any substance that would not allow the free flow of moisture from the wood. However, on the end grain where cracking is a concern, the wood should be sealed with wax or glue.
If cracks do start to develop, do not hesitate to wick some low viscosity cyanoacrylate glue into the crack (use LMI’s FGHO “Hot Stuff” super glue). If the crack is thin and the edges of the crack mate perfectly, it will be virtually invisible after sanding. The glue will bind the crack and it will cease to move further into the wood. Cyanoacrylates are used in this way when cracks develop when bending the wood with heat. Often the luthier’s skill is divided between avoiding these sorts of problems and successfully healing them without leaving a trace!
The interactions between wood and moisture warrants greater research and there are good articles in Wikipedia online and in the Bruce Hoadley’s classic book ‘Understanding Wood’ (LMI product code BM28).