[last update 8/2014]
...The top plate (belly) of the instrument is made of spruce wood; quarter sawn grain; of medium width growth rings; and it needs to be well (and naturally) aged. {sometimes slab cut for one piece plates}
...The quarter sawn means that the grain (tree growth rings) appears to run straight up and down when viewed from the end of the plate wood (laying flat on a table). It can be made of one piece but is often not wide enough so it is 'book matched' {carefully fitted and glued together} to make a piece of wood large enough to make the plate.
...The plate shape is carved from this solid block of wood: first the outside surface is carefully shaped to its finished condition. Once the outline is defined, the perimeter is cut out and finally shaped. Often the purfling strips are fitted before further work. Only when the outside of the plate is finsihed is the plate turned over and the the plate is then 'graduated' {dished out to a specific pattern of thichnessing, which will largely determine its playing characteristics.}
...There are several varieties of spruce used in instrument making. Much of the spruce used on instruments is harvested in Europe on the foothills of the Alps mountains (in various countries).
...Spruce grown at high altitude on the west coast of North America also makes good instruments. Here the two leading varieties are Engleman spruce and Sitka spruce. Wood grown at high altitude has the closer grains spacing needed for instrument making and if grown in a severe winter area the wood will grow strong to stand the strains of winter storms and cold.
...Spruce wood is light for its strength and transmits sound at a high speed. Sound travels at different speeds in different materials but almost as fast in spruce wood as in steel (about 4,500 feet per second). [Sound in air travels about 1,100 feet per second.]
...The back plate, neck and ribs are made of matching Maple wood. Again several species are acceptable. The famous violin makers of Italy imported their maple from Bosnia, both for its beauth and rich sound capacity. A beautiful back wood piece will sell for around $ 200 to $ 300, the neck block for $100. Usually the ribs can be bandsawed from the piece for the back. Other fine wood comes from around central Europe with costs being about 1/2 the above for beautiful examples. Plain grained examples of the same wood can be purchased for $40 for the back and $15 for the neck block.
...If you are working on one of your first violins then the lesser attractive wood might be the best choice. The sound will not be hurt by the plain figure (it might even be improved). However if you have aquired some skill and want to build a special instrument, then the cost of the wood, expensive though it is, is really not excessive.
{ The broad leaf maple varieties of North America have also been used to make fine sounding instruments by some accounts.}
...The top plate and back plate each can be made of two narrow pieces joined in the center with a glue joint ('book matched') or of one piece if it is wide enough. Usually the one piece tops and back are used on more expensive instruments.
...One piece tops can be made of close grained spruce but the trees must be 200 to 300 years old to get wide enough so that a one piece top plate can be fashioned from a quarter-sawn board which must be cut out from the center of the tree toward the outside and not include the core grain of the tree.
...One piece maple backs are normally only available when the tree trunk is cut into slabs and the slab near the center slab of the tree trunk is used to make the one piece back wood. The grain is not quarter sawn but is a simi-circle when viewed from the end of the board. the concave side is made to face the inside of the instrument (as sound travels around the growth rings, which then matches the arch of the back plate.
...As the grain of a tree is growing, it often grows straight up, but sometimes also curves back and forth (see photo above). This can be both a positive or negative feature for the instrument maker. If we cleverly cut out our plates to take advatage of this natural curve to match the arching of the violin plates (as viewed from the side of the plates) then this will make for a better tone and more power. However, If we turn the wrong side up then we be cutting across the grain more which hurts sound transmission.
...For instance in the example at left we would want to cut out violin plates as illustrated:
...Another thing to be concerned with it that different parts of the tree will transmit sound differently. Tap along the plank before cutting out for your plates and mark those areas that are more 'dead' or 'hollow' sounding. also mark those areas that really seem to carry sound. Discard those poor areas and only used the wood that is 'alive'.
...This internal grain curve can be seen by cutting a thin slice off the side (toward the out side of the tree) with a band saw. Carefully mark the piece for reference. With a splitting wedge, start a split in the center of the piece. By observing the grain movement, you can orient the plate wood correctly. That is the high part of the curve needs to be in the center of the plate facing toward the outside of the instrument.
side view of a tree trunk.
...This internal grain direction can also be detected and identified by tapping along the center of the plate wood. (Only tap along a line of constant thickness as tap tone is influenced by wood thickness). As you tap down the centerline of the plate wood note how the tone changes. What we are listening for is changes in the overtones of the wood as the base note (frequency) will be the same if the thickness is the same. The piece we want to select is the one that has the highest tone in center of the plate and lowest at the two ends. This side goes toward the outside of the instrument. If you turn the same piece of wood over and repeat this tap test, you will discover that on the other side the low pitch is in the center and the ends have a (seemingly) highter tap tone. This means that that side should be turned toward the inside of the instrument.
...What the tap tones reveal is illustrated below:
highest tap tone in center
this side= outside of instrument.
{Red line represents the grain runout of the wood.}
(taps under piece are just opposite)
side view of the piece of wood for one of our violin plates
...Only use wood with this grain orientation for best results. It may be obvious to you that if you are book matching wood for the plate; that is cut out from a wedge {either sawn from or split from the tree} then once you find a piece with the above grain curve orientation, that the matching piece must be rotated 'end for end' before book matching or else one half will be orientated correctly to follow the natrual wood grain arching shape and the other half will be wrong side up. In other words, check each half of the two part plate and adjust the orientation so it is as above before gluing together.
...If the piece of wood you are testing is even toned from end to end, it means that there is no grain run-out. This wood will made a good instrument and either side may be placed 'up', but not as good as one which has the natural grain curve to match the plate arching (as viewed from the side) when this is oriented properly.
The way to cut out a slab cut for a one piece back.
The outside surface of the plate
(orient toward the outside of the instrument).
Cross-section through a tree trunk
...Some general tips for woodcutters is to only use wood cut in the dead of winter, and preferably during the dark of a new moon. {this will minimize sap in the wood}.
...Select a tree that stands by itself so the winter storms directly bear (so it will have grown stronger than trees nestled in dense grooves).
...Select a tree from the southern facing slope of a hill (toward the winter sun) and use wood from the sunny side of the trunk for best tone. This side of the tree trunk will be thicker (for identification purposes) and since the tree tends to grow toward the light it will lean out somewhat putting this side of the tree in compression all the time (which may be good for sound transmission; for instance, the grain of the top plate of a violin will always be in compression due to the load of the tensioned strings, so this might be an advantage for top plate wood.)
...I have read that the wood from the sunny side of the trunk will produce a warmer tone and the wood from the shady side will produce a colder tone. Again, the thicker side of the trunk (from the center to the outside) is probably the best bet for violin plates; this being the wood from the sunny side of the tree trunk.
...The wood is normally naturally cured by stacking, putting sticks between the (slightly oversized) pieces to promote air circulation, and keeping it inside for a period of years; at least five years, with twenty years being even better. In some way, this is said to promote good tone from the wood when it is eventually used for instrument making.
...One thing is for sure... if the wood selected for your instrument is not ideal for the purpose, then your insturment begins with a permanent handy cap which will limit its success.
..Tree selecting and cutting family from Northern British Columbia, Canada. They specialize in finding Engleman spruce trees that have died of natural causes and harvesting and using the wood for instrument making. (we have used their wood on several instruments).
(c) 2014 by David Langsather