Woods to Know - Bamboo

Woods to Know: Bamboo

Bamboo (Poaceae family)

by Peter MacSween

North American woodworkers were first introduced to bamboo in the 1990s when manufactured bamboo flooring arrived. Since then, many new bamboo products have arrived. Turning blanks, sheet goods, solids and veneer are now available. These raw materials have found their way into cabinetry, furniture and products such as cutting boards and decorative items.

The key to working with bamboo is to understand how it is different from the hard and softwoods we are used to using. Bamboo is a grass and has no growth rings. The stems or culms are hollow and vertical sections of the culms are separated by solid nodes. There are over 1,400 species of bamboo in 120 different genera. They grow worldwide in mostly tropical regions including Asia, Africa, South and Central America. Most of the bamboo we see is harvested from South East Asia.

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Bamboo, especially those in the genus Phyllostachys (commonly called timber bamboo) can grow up to 90 feet tall with 12 inch diameters. Most bamboos grow 15 to 30 feet in height with 4-6 inch diameters. They are extremely fast growing with some species growing up to 3 feet per day. The culms start growing from the ground at their final diameter and reach their maximum height in their first year. The culms harden over the next 2-5 years. on average. depending on the species. Eventually, fungi infiltrate the culms, and they collapse and die. Typical life spans are 3- 8 years and new growth is a continual process.

The culms are harvested to maximize hardness and durability. They are sliced into smaller strips, which are machined square, dried and glued up into sheets or larger billets. Bamboo fibers can also be processed into larger structural pieces. When the strips are glued up the with the faces showing the nodes are visible. When the edges are shown, a very linear appearance is created. Bamboo products can also be carbonized, a type of heat treating which gives the bamboo a smoky appearance.

Bamboo has a very uniform texture, medium to fine depending on the species. It has a very high strength to weight ratio and is strong in both compression and tension. Bamboo has a high silica content, so carbide tooling is a must.  It will tear during cross cutting operations. Using masking tape to hold down the grain can help as well as pre-scoring the cut line with a sharp knife. It can be turned, but tools will have to be frequently sharpened. It glues and stains well. Sanding presents no problems with the face and end grain sanding equally well. Nails and screws should be predrilled.

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Bamboo end-grain

Bamboo can have stability concerns especially when drying. Laminating bamboo products help minimize this tendency towards movement in service. Quality can be a concern since such a wide variety of bamboo species can be harvested. Bamboo must be harvested at the right time or it can be weakened or discoloured from fungal attack.

Bamboo is considered a renewable resource, important in this age of dwindling resources. While bamboo itself is cheap, most of the manufactured products can be expensive due to the amount of processing required. Bamboo sheet goods and veneer are now common. Larger dimensional lumber is harder to source. I expect this to change as demand increases. In fact, it is now possible to buy houses constructed out of bamboo. This truly is a species with a future. Woodworkers should consider it for a wide range of projects, especially those that would benefit from its distinctive nodal or linear appearance.

 
Average Dried Weight31-53 lbs/ft³A measure of its weight at 12% moisture and an ambient temperature of 70°F.
Specific Gravity.50-.85A measure of the ratio of its density compared to water (at 12% MC)
ShrinkageDiameter: 10-16%
Wall Thickness: 15-7%

 
Radial (the amount of crosswise shrinkage);
Tangential (the amount of lengthwise shrinkage);
Volumetric (the total amount of shrinkage.)
Janka Hardness960 lbfA measure of resistance to denting and abrasion.
Crushing Strength1,410-1,610 lbf/in2A measure of compression strength parallel to the grain.
Colour
Generally a uniform and pale yellow to almost white. Live bamboo that has been left standing too long frequently develops fungal decay, discoloring the wood with brown or black streaks and patches.
GrainBeing a monocot in the grass family, bamboo does not have any sapwood/heartwood or growth rings.
TextureTexture is very uniform, and ranges from medium to fine depending on density. Bamboo that has been split and processed into lumber will have intermittent variations in the fiber at each node on the stem.
Workability
By woodworking standards, bamboo can be different. It is not necessarily difficult to work with, but depending on the species, it may require some special care. Bamboo fibers tend to split and pull out when being cross-cut, (applying masking tape across the cut line beforehand is recommended to prevent this sort of tearout). Carbide cutters are strongly recommended, and surface sanding is suggested instead of thickness planing with steel cutters, both for longevity of cutting edges, and quality of the finished surface. Bamboo glues, stains, and finishes well. When turning giant bamboo species, tools dull quickly, and endgrain tearout is common, but tearout tends to be very shallow, and the endgrain sands nearly as easily as the facegrain, and an overall smooth finish can be achieved with minimal effort.
Uses
Veneer, paper, flooring, fishing rods, ladders, scaffolding, musical instruments (flutes/woodwinds/chimes), furniture, window blinds, carving, turned items, and small novelty items.
Price$354.75 - 4' x 8' Solid laminated Moso
$265.00 - 4' x 8' 3/4" Plywood sheets
 
  
Photos and Specifications Courtesy of: The Wood Database