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26th-Dec-2013

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Seasoning violin Wood



                                 Seasoning Violin Wood


1.Seasoning  :

Wood that has been newly converted from a Log (Green Wood) – contains a
very high percentage of moisture. The Cell walls of the wood are
saturated and the free water is contained within the cell cavities.
Seasoning the wood is the process of removing the free water from the cell
cavities and also much of the moisture from the cell walls.

This process must be begun within a week of the wood being converted,
otherwise the wood is likely to rot because of the fungal growth. As the
wood dries , the free water is lost from the call cavities until only the cell
walls contain moisture.
This is termed the “ FIBRE SATURATION POINT ”.(F.S.P.)  
and occurs at about 30% moisture content, depending on the species.

 

FSP graph seasoning article 001

                   ( OD=Oven Dried    KD= Kiln Dried  AD= Air Dried )


It is when the moisture starts to be lost from the cell walls that the shrinkage
begins. The loss of water will stop when it is in balance with the humidity of
the surrounding environment.
This is known as the “EQUILIBRIUM MOISTURE CONTENT “(E.M.C.).
 

EMC graph seasoning article 001

 
For wood to be used for making instruments  (With Spruce and Maple) , it
must be kept indoors in a heated room.
However, the difference in moisture content, between the cells and the
outside air        “ VAPOUR GRADIENT “(V.G.) , must be brought to the
(E.M.C.) gradually otherwise many deforming  side-effects will occur.

Bowing (Curvature along the face of the board)
Springing (Curvature along the edge of the board, where face remains flat.)
Winding (Twisting of the board)
Cupping (Curvature across width of board)
Splitting (Splits that develop along the grain of the wood)
Collapse (Cells collapse)
Case hardened ( Inside of the board is Dry but moisture is trapped in the
centre cells of the wood. When the board is resawn it will tend to twist)


 

wood defects seasoning article 001

        ( Defects in the Wood are related to the direction of annular growth )


For most Hardwoods and therefore Maple, it takes about 1 YEAR  to dry every
25mm (1 inch) thickness.

For most Softwoods , therefore Spruce ; it takes about 6 months.

This time scale is based on the AirDrying method of Seasoning; however ; this
method will only reduce the wood moisture content to around 14% to 16% .

Therefore; further drying time is necessary which will take place indoors.
The total time needed for seasoning boards of thickness  35mm is about
3 years for Spruce  and 5 years for Maple.
The other reasons why proper seasoning is necessary are as follows;

    (i)   Dry timber is easier to work with than very moist timber.
    (ii)  Moint timber will not readily accept glue., dyes, pigment, or varnish.
    (iii) Moist timber will warp and deflect during the drying process.
    (iv) In general dry timber is stronger and stiffer than wet timber.

 

 





2. Grain Structure:

The mass of the woods cell structure constitutes the “Grain” of the wood,
which follows the main axis of the tree’s trunk. The nature of the
grain is determined by the (Cellular specialization) degree of orientation, and
environmental factors;
notably Seasonal weather, (Spring, Summer / Autumn, Winter)
and available nutrients,  Oils ,Resins, and minerals, also contribute towards
density.
 

Certain Species of Pine ( Family Spicerae) for example
“ Picea Abies”  (European Spruce)  &  “Picea Stichensis”  (Sitka Spruce), are
ideal for the violin Front plate.  Selected sound boards have to  meet specific physical criteria which exhibit  ideal characteristics of,

     (i)     Strength;       (ii)    Flexability; and        (iii)   Density

In order to exhibit excellent sound amplification.

Much of the tree grows very straight.   This “ Straight  “characteristic Growth, in particular the straight Late growth ,  (which are more dense than the early
growth , and are the principle vibration conductor), distribute the sound efficiently across the surface of the Violin front Plate.
For the violin a grain width of approx. 1mm is typical between the late growth
rings and the early growth rings, from the centre line accross most of the
Violin Front plate, widening out towards the edge.
( The increased grain  width towards the edge provides extra flexibility so that
the Violin front can fulfil its role well as a diaphragm.)

 

The density which is  typical  for the Violin fronts   in
 “ Picea Abies”  (European Spruce)  is around 470 Kg/M at 15% moisture
content.
Also in , 
“Picea Stichensis”  (Sitka Spruce),)  is around 430 Kg/M at 15% moisture
content.

The wood for the Front should be Quarter sawn for maximum strength with
Medullary Rays parallel to the top of the ribs.
The wide edge of the Quarter Sawn Wedge must also run parallel to the Grain.


Violin Wood Selected for the back of an instrument, must be a much harder,
rigid wood than that for the Front (Belly); however , still having the necessary
degree of flexibility and density.

Maple of the (Family  Aceraceae) , for example
“ Acer Platenoides “ ( Bosnian or European Maple)  and the density which is
Typical for this is 660Kg /M at 12% moisture content..


Maple used for instrument making has a certain amount of “ Flame ” to a
greater or lesser degree, an optical effect caused by the different angles of
reflection of light caused by the wavy pattern (the changes of orientation )  in
which the “Trachieds” were laid down.
Flame does not appear to have an adverse effect on the sound of an
instrument, though figured wood is weaker than plain wood and more difficult
to work.

There are other woods with similar suitable characteristics which could be used for the back.
Popular (“Populus Canadensis “)
 - Black Italian Popular has a Density of 450Kg /M at 12% moisture content..

 - Willow (“ Salix Alba “)
-Common Willow has a density of 450Kg /M at 12% moisture content..

 Both have been used by Stradivari.  Pear and Beech have been used by certain
German and French makers, be it  part of a mass production setup.

 However , Maple of the right density is generally deemed better acoustically , and looks more attractive .

 

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