How to spot quality timber
For many luthiers it’s important to use the right type and quality of timber in their instruments. This is for a number of reasons including stability, aesthetics, stiffness and acoustic radiation. For example it has been well understood that a quarter-sawn (radially sawn) soundboard will be more stable and have a greater velocity of sound than a back sawn (tangential or slab sawn) or rift sawn piece, everything else considered equal. Many instruments will use a back sawn neck (grain running perpendicular to the fingerboard) for strength once string tension is applied. Certain parts of an instrument require the grain to run the length of the piece; such as side sets that require tight bending of a thin veneer - grain run-out will encourage breakage and increasing dampening effects. Quilted maple needs to be back sawn to some degree in order to expose this type of figure. For these reasons it is important to be able to determine the attributes of the piece of timber you are selecting, most notably grain direction.
Grain direction
The direction of the grain can be determined in a number of ways. The easiest way is to look at the end of the block and see what formation the growth rings are in. From here you can see if the block is quarter sawn or back sawn or something in between (rift sawn). However, you can only uncover part of the picture. You are yet to determine if the grain twists or runs out over the length of the piece. You can do this by looking at the other sides to see if the growth ring lines and pores are straight or deviate. If you are only shown one face of the block you can still determine if there is runout and if it is quarter sawn or slab sawn by looking at the length of the pores, the hue of the piece, the presence of medullary rays and the spacing and direction of growth rings.
Pores and Hue
Here we can see the different grain directions by looking at two different characteristics - pore length and hue. Where the grain is straight with the block the pores are at their longest - almost 4cm in this example but usually about 2cm. As the grain dives out at the flame ripple we can see the pores reduce in size to about 1mm. This is how we can determine the degree of runout, by the length of the pores. At the flame ripple the hue is either lighter or darker than the rest of the block. This is another giveaway that there is long-grain-runout. The flame ripple doesn't affect the overall angle of the piece but can be used to show how run-out appears.
Pore length can only be used to determine the degree of runout, it cannot be used to determine if it is quarter sawn or slab sawn. Since we are unable to see any medullary rays we know that it is not perfectly quarter sawn. So for this piece we can tell that in general the piece is straight with the length of the block and is rift-sawn to some degree.
Medullary Rays
This piece shows us that it is quarter sawn by the presence of medullary rays on the left-hand-side. It only takes a slight move away from quarter for the ray flecks to diminish in size dramatically and almost not be seen, as depicted to the right-hand-side of the photo. The pore length is also long, suggesting no long-grain run-out.
Rift Sawn, Ripple and Growth Rings
This piece shows the enhanced level of quilting as the grain becomes more back sawn. This usually only occurs when figure is projected from the tangential plane, such as this stump flame or typically in quilted maple. The lower left corner is completely back sawn whilst the upper right is half way between quarter and back - rift sawn. We can tell because the growth ring lines are spaced further apart in the bottom left corner and each dark section of the ring is a lot wider than could normally be seen from the end-grain – it is cut on the same plane as the growth rings.
Quilting v's Fiddleback
In these two examples the major difference is that the "wiggle" of the grain is running on separate planes.
To clarify, stump and crotch flame are different to quilting in that quilting is a unique type of figure that can occur throughout the tree and looks much like bubbles or lumps on the outside of the tree. Quilting is often used as a general term for anything that looks like interwoven fiddleback. We will use the term flame for wavy grain emanating from the tangential plane, to avoid confusion with quilting and to distinguish it from fiddleback.
Quilting, stump flame or crotch flame will be enhanced when the timber is back-sawn, since the "wiggle" is diving in and out of the tangential plane. When quarter-sawn it will show growth-ring lines that dive in to the heart of the tree and out towards the sapwood, across the piece, but it will not give the same chatoyance (3D appearance) compared to if it were back sawn or rift sawn. Flame in Blackwood can look very appealing when the contrast of the white sapwood wiggles into the dark heartwood.
In contrast, fiddleback dives in and out of the radial plane. This type of figure will be most enhanced when quarter sawn but will also give stunning effects when rift sawn. When rift sawn the fiddleback is presented with more of a "sand-dune" look compared with a "straight-line" look when quarter sawn. When completely back sawn even the most crazy fiddleback will appear mild.
Both types of figure will give a similar appearance when rift sawn but there are a few ways to tell if the figure you are looking at is flame or fiddleback. In Blackwood flame always has larger waves, much larger than fiddleback blackwood. Flame will usually only occur in the stump of the tree or near a branch, so the grain will usually have a curve to it. If it's straight, it's likely fiddleback. This is because flame (in Blackwood) occurs when the tree growth is confined and bunches up when it grows out from the tree.
Figure
Figure is a natural formation in timber, in which the grain of the timber is altered. Such altered grain formation often results in aesthetically pleasing patterns such as fiddleback, flame, burl, mottle, birds-eye, quilting, maiden’s tears and dimple, to name a few that occur in Otway Blackwood. Below are descriptions of our figure grading. Examples are shown for fiddleback but the descriptions can be extrapolated for any figure type.
A Grade
Generally speaking A grade timber has no figure. It is free of blemishes, knots and grain swing. As with all Blackwood, there will be a large variety of colour (red cedar to walnut), density (430-900km/m3) and growth-ring width (2-12mm).
AA Grade
Figure mild yet noticeable but may not reach across the entire width of the piece. It may be patchy through some areas and the figure will not have the depth compared with AAA grade.
AAA Grade
Consistent, highly figured timber that is present throughout the piece. Increased depth of figure.
AAAA / Mastergrade
Extreme figure. Figure depth near maximum for species. Visual throughout entire piece. May contain spur (stump) or crotch flame.
Figure Formation
From experience in assessing Blackwood trees for figure, such as fiddleback, we can suggest that it is not directly related to size, age, or environmental conditions such as soil type, rainfall, temperature, elevation and aspect. Although these variables may have some effect on flame formation they are not directly related. There is definitely a genetic component since only one in 100 trees may exhibit figure in the same area. Pacific Rim Tonewoods have been growing both Maple and Koa, that exhibit fiddleback, from parent trees that were figured. Suggesting that there is a genetic component to it.
Fiddleback is thought to form after initiation of cambial division where uneven cell elongation occurs. The ends of cells are restricted for space and central portions of the cell are pushed to either side, particularly when they encounter ray cells (Beals and Davis 1977).
But to be honest we just don’t know why these different figure types form. There are a lot of theories and it’s kind of nice keeping it a mystery. Blistering bubbles and dimples, birds-eye, cones, bear claw, maidens tears, quilting, rippling, curly, crunchy fiddleback …. we can only wonder.
Dimple - Back Sawn
Maidens Tears - Quarter Sawn
Birds Eye - Rift Sawn
Stump Flame - Rift Sawn
Fiddleback - Quarter Sawn
Coning - Quarter Sawn
Few studies have attempted to explain the processes involved in figure formation but the study by Beals and Davis (1977) helps explain some of the types in further detail:
Beals and Davis (1977) - Figure in Wood: An Illustrated Review.
After having an understanding for grain direction and figure you can then look at different species characteristics to fine tune the right tone for the job.