“Is that a crack?” About once a week, I am asked this question. Some of the times, its about furniture which has been purchased elsewhere. Other times its about our own furniture. It might have been custom made or simply the customer purchased it from from a moving sale. Some pieces might have traveled the globe and eventually landed in a dry climate – a once beautiful stable piece, is now turning into a cracking, splitting mess. But rest assured, at least once a week, I am asked this question.
Solid wood/old wood vs. veneer and composites
When making furniture,
Solid wood furniture is strong, long lasting and can be re-sanded, re-finished and re-stained for years to come. That’s the good news. The bad news is, this comes at a price. Since wood is a natural, living, breathing material, it therefore has a tendency to swell / shrink, warp and/or crack as it ages, in relation to environmental changes in temperature and humidity. In door environments, in particular modern homes where dry electric heat is used, will accelerate this process. If the furniture is painted or lacquered, this presents an even bigger problem as the lacquer covering the outer surface will crack (often badly) when the wood underneath expands and contracts.
One way furniture makers attempt to compensate for this by using aged wood and reclaimed wood. While all wood, including old wood continues to breathe and change, unlike new wood, old wood has (theoretically) already reached its critical drying point over many, many years. Unfortunately access to reclaimed wood depends on the supply of old wood (often from buildings) which may not always be available in large quantities. Aged wood may also have a certain amount of dents, nicks and other characteristics that come along with age. And because its still real wood, this means it will still breath and change to some extent.
A second method of compensation is by using air dried or kiln-dried wood. Air dried wood, which has been exposed to outside air for extended periods of time, is often harder, though tends to have a higher moisture content and may take months or even years to dry. Kiln dried wood can be ready to use in under a month, but is softer as the artificial heating process stops the wood from naturally hardening any further. The heating process may also cause defects in the wood such as the “honey comb effect.” Unfortunately many smaller factories do not have kilns as the process is costly and requires specialized technical expertise. Even large modern factories shipping 200 containers a month may find running their kilns to be expensive and technical. Therefore because Kiln dried wood must be either pre-purchased or sent out for drying, air drying is the most common method in use for smaller workshops.
The third and most common method today is the use of wood veneers and composite woods. A veneer is a thin sheet of wood affixed to a underlying layer of plywood, pressboard or MDF (medium density fiberboard consists of finely ground wood particles bound together with a resin). Other composites are like thin layers of wood, sandwiched together for extra durability. While a common perception is that these materials are weaker and less costly, in many cases composites may cost as much as solid wood, and even be heavier and stronger. If the veneer is relatively thick, it can even be re-sanded and refinished in the future as well. Good quality veneers and composite “man made” woods are also chemically dried and treated and thus extremely stable. Generally if treated properly, venners will not expand, contract or buckle in relation to the climate or humidity.
In many cases, the average person cannot tell the difference between solid wood and a veneer. For this reason much of what’s available on the market today is in fact made from veneers and composite woods. Unfortunately because there is a stigma attached to veneers with many people believing a veneer is inferior to solid wood, manufacturers often advertise their furniture as being solid wood, when in fact its actually “solid wood veneer” – a closer look at the fine print will often reveal this.
Splitting & cracking vs expansion & contraction.
Cracking is a side effect of solid wood that is either not properly dried or simply not dry enough relative to its environment. As the wood expands or contracts according to its environment, the movement gradually builds pressure, which in turn stresses the joinery. Cracks and splits then begin to occur allowing the wood to release this built up tension.
Over the years, Chinese joinery developed a method for wood to both expand and contract without stressing the wood or joints, through a technique called “floating panel construction.” In dry climates, the “floating” wood panel will contract in the frame, without splitting or cracking. Alternately, in moist climates, this same “floating panel” will expand without stressing the joints and frame.
This is an important distinction, as one is deliberately engineered (expansion/contraction) where as the other is accidental (splitting/cracking). About 50% of the time, the piece in question is in fact not cracking but rather contracting. Unfortunately many people don’t see the difference. A contraction is normal if the home / climate is dry. Rest assured this means the floating panel technique is properly doing its job. The alternative is cracking and as we can see, the results are not pretty.
A floating panel on the top of a desk, properly doing its job. Only a bit of stain is required as a touch-up.
A major crack in the wood requiring repairs.
Making the right decision:
If your furniture is to be painted or lacquered, then composite woods like MDF are generally the best choice, as solid wood construction will likely cause major problems over time (lacquer is extremely stable ,but because the wood underneath is not, cracks and splits will occur in the lacquer as the underlying material shifts and contracts). Unless you plan to strip the furniture down and refinish it completely years down the road, you best choice is to use composites and veneers.
If your furniture is to be stained and (with the wood grain visible), then veneers are preferable for any panels and faces (places which are most likely to expand or contract).
Solid wood such as air-dried/kiln dried or reclaimed wood, is also a choice, however you must be able to accept gaps caused in floating panel construction and the potential for cracking / splitting.
A bit of luck?
When problems occur, sometimes the issue is joinery related. Other times improper use of wood glue might play a role. And sometimes? Well, sometimes it simply comes down to a bit of luck. 😛 In the case of hand made furniture, the construction techniques used may have been employed for hundreds of years. Sometimes this creates challenges not foreseen when such techniques were invented. Like modern homes with air conditioning and dry central heating, children likely to spill soft drinks everywhere and heavy TV sets sitting on the top.