Humankind’s relationship with wood goes back to the dawn of human evolution. It feeds us, houses us, and even clothes us – bamboo is the new cotton.
No other material has been as intimately associated with our development as a species – from the discovery of fire for warmth and cooking; to great ships of the line and the progression of mans’ shelter from simple thatch to magnificent buildings of today’s civilisations. Lastly, let’s not forget that wood was arguably the first material to be used as furniture within our homes, evolving to the exquisite pieces produced by master craftsmen over the centuries that continue to inspire us.
Today, solid wood is still one of the most luxurious materials we can use in our home.
Designing with wood is a beautiful experience, however as a natural material it needs more consideration than say plastic or steel.
The two properties of solid, natural wood that must be taken into account when designing furniture are called ‘hygroscopic’ and ‘anisotropic’.
Hygroscopy is the “phenomenon of attracting and holding water molecules from the surrounding environment, which is usually at normal or room temperature”. As a natural material, wood needs to breathe – as we do. As it takes on ambient moisture, the material expands, and as in turn contracts as it releases that moisture back into the air.
The second is that it is anisotropic, meaning it expands and contracts to differing degrees along the grain where it is stronger, as opposed to across the grain. Man-made boards, such as MDF, plywood, supawood, and veneered boards also contain material from trees, but it has been broken down and reconstituted so that it no longer has these natural properties.
It is only natural, solid woods that have these unique properties, and designing with this is mind is part of the beauty of the process. So how do we here at Africa Touch work with nature?
When we finish a quality furniture piece a finishing coat is normally applied. Depending on the type of finish used, this can slow down the effects of the hygroscopic (moisture retention) properties of solid wood. However it is with the design where we need to begin considering the two conditions, well before the finishing coat is applied.
Unscrupulous furniture makers will sometimes supply a piece that looks great, and is finished well, but within a relatively short period of time will start to show signs of failing, simply because it has not been properly designed and built to accommodate the natural movement of the wood.
So how do we apply design rules to overcome these effects?
There are three main principles when designing with solid wood that offer solutions to counter the effect of wood movement. Below we offer examples of ways we work with these principles to create a solid, long lasting piece that retains all the beauty of the material.
A wide solid board
In the case of the tabletop, to prevent warping we construct the support base with timber beams that stretch almost all the way across the top. We then embed bases of steel brackets into the underside of the table top with the bracket itself fitting into a slot in the timber beam which keeps the top flat while allowing it to expand and contract sideways with variations of moisture content. The picture below illustrates how this is done.
A large panel
When dealing with a large panel such as a cabinet side or door, the best solution is to build a grooved frame into which a panel slides before the frame is joined together at the corners. The panel outer dimensions are less by several millimetres than the internal dimensions of the grooved frame, allowing the panel to expand and contract within the frame – in essence so the wood can breathe. Here is what Fine Woodworking, Americas’ premier publication for professionals, has to say about this method:
“Frame-and-panel construction is a popular method for making doors, cabinetry, and a variety of furniture and architectural components. Its primary purpose is to create a large panel with minimal wood movement. Whereas solid wood shrinks and expands with changes in humidity affecting its overall dimensions, a frame and panel doesn’t. Instead, the panel is able to expand and contract freely inside an unchanged frame.”
Timber joined across the grain
This picture shows a beautiful door in which the upright timbers of the door are joined to the top and bottom rail, with the grain running in opposite directions. The effects of expansion and contraction are overcome by connecting the uprights to the rails with what’s called a mortice and tenon joint, and the uprights join to each other with a sliding tongue and grove profile. This allows each timber piece to expand and contract relative to each other, as the panel moves within a frame.
It’s our mission here at African Touch to deliver to you a well designed, beautiful piece that will keep on functioning for years to come. Now you know a little more about how we are able to do that!