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As drummers we spend a lot of time discussing the various types of woods used to make drum shells. I thought it might be interesting to provide a little insight as to the hardness and density of these various woods. You'll notice that I've gone ahead and included many woods that are not commonly used in drum shells, even custom drums. The reason ... to provide a means to compare these various woods, and possibly gain a better understanding as to why certain species of woods are used while others are not ... beyond the sonic properties. Perhaps you can take this information and do your own research, comparing between known hard and soft woods.



WOOD HARDNESS

It's common to use the Janka test when determining a wood's hardness, especially when it comes to wood flooring. Although we are talking about drum shells and not flooring, a wood's hardness is determined regardless of how it will be used. The Janka hardness test measures the force required to embed a 11.28 millimeter (.444 inch) steel ball to half its diameter in wood. This is one of the best ways to measure a wood species ability to withstand denting and wear, as well as how difficult it may be to saw, nail or bend. The chart below includes some of the most common woods used to make drum shells. The higher the number, the harder the wood.

In alphabetical order:

WOOD HARDNESS *   DENSITY
         
Ash, White 1320     0.63
Bamboo 1800      
Basswood 410     0.38
Beech 1300     0.68
Birch, Yellow 1260     0.66
Bloodwood 3300      
Bubinga 2690      
Cedar, Western Red 350     0.33
Cherry, Black 950     0.53
Cherry, Brazilian 2350      
Cypress, Austrailian 1375      
Fir, Douglas 660     0.52
Hickory, Pecan 1820     0.69
Iroko/Kambala 1260      
Lacewood 840      
Jarrah 1910      
Lignum Vitae 4500      
Mahogany, Honduran 800     0.45
Maple (Hard) 1450     0.63
Merbau 1500      
Mesquite 2345      
Oak, Red 1290     0.65
Oak, White 1360     0.65
Padauk, African 1725      
Pine, Southern Yellow (short leaf) 690     0.54
Pine, Southern Yellow (long leaf) 870     0.62
Poplar, Yellow 540     0.46
Purpleheart 1860      
Rosewood, Honduran 2200      
Teak 1000     0.56
Walnut, Black 1010     0.53
Wenge 1630      
Yellowheart 1820      
Zebrawood 1575      


* The above measurements where taken from the Wood Handbook: Wood as an Engineering Material, U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. The hardness value is in Jankas or lbf (pound-force).

 

WOOD DENSITY

There are two primary factors which affect the weight of wood: density of the basic wood species and the moisture content. A third factor can be included in this (minerals and extractable substances), but it only has a measured effect on very few species of wood.

Excluding water content in wood, the density varies quite a bit between woods. It can be said that the density of most species of wood falls somewhere between 320 and 720 kg/m3 (20 and 45 lb/ft3), although there are a few that land well outside this range, both higher (some imported woods) and lower (balsa).

Since moisture makes up a substantial part of the weight of each species, the density value must reflect that. It is with this fact that the density of wood is often determined by it's moisture content.

The calculated density of wood, including water content, is usually based on an average of the given species characteristics. The final value is an approximation since there are natural variations in the wood's anatomy, moisture content, and the heartwood to sapwood (not discussed here) ratio. This average is typically accurate and sufficient enough for wood products where weight is important.

Now, in order for the comparison of woods to have some sort of standardization, the specific gravity is used as a reference base, rather than density. The traditional definition of specific gravity is the ratio of the density of the wood to the density of water at a specified reference temperature (usually 4.4oC or 40oF where the density of water is 1.0000 g/cm3). There are common bases for determining specific gravity, such as ovendry weight and volume at green, ovendry and 12% moisture content, but let's not get into all of that. To reduce confusion introduced by the variable of moisture content, the specific gravity of wood is typically based on the ovendry weight and the volume at some specified moisture content.

When all is said and done, the density figures I've provided in the table above is actually the specified gravity for each species of wood. I just labeled it "density" because that's a term we are all familiar with, and it's not entirely inappropriate. Unfortunately I've been unable to acquire the density figures for all wood species, but I'm working on it. I'll add to this list as figures come available. Keep in mind that these figures are not exact, and a variance of 10% is to be expected and common.

 

Bart Elliott Bart Elliott is a degreed professional musician and founder of the Drummer Cafe. His 35+ years in the music industry, over 100 albums to his credit, as well as his understanding of contemporary and classical music, makes him a complete and skilled master musician. A highly sought after drummer and percussionist, both live and in the studio, Bart is widely known as a top music educator and gifted teacher, appearing as a guest artist and clinician throughout the USA.