" " wisno wood furniture finishing: Crack in the wood furniture

Monday, November 29, 2010

Crack in the wood furniture

 crack in the wood furniture

The wood cracked in the furniture is the quite common problems in the wood furniture industry. Wood is a hygroscopic substrate; he will always absorb or release its moisture content when he is exposed in open air. The wood always try to balancing its moisture content with the humidity of his environment. The wet wood will release its moisture, while the dry wood will absorb the water from the environment air to balance its moisture content with the humidity of the air environment. It means that the moisture content in wood will change to follow the humidity of its environment. And the changes in the wood moisture content will always followed with the movement of the wood. Wood will shrinkage when he release its moisture, and expand when he absorb water. The volume of the wood movement will vary depend on the type of the wood, direction and the length. If the movement of timber is quite big it will result in crack on the wood. 
Since the wood movement was mainly influenced by its moisture content, many effort are intended to keep the moisture content in the wood is stable. The finishing process is one way to make the moisture content in the wood become more stable. The layer of finishing materials will coat and cover the wood pores and grains and reducing the wood sensitivity to its environment.
But sometimes there many cases of broken wood or veneer in the finished furniture are still happened. It usually occurs when wet wood is used to manufacture the furniture. Finishing layer that coats the wood surface may help to stop the water outside to come into the wood, but it always cannot withstand the water from inside the wood to release. Therefore to prevent the crack problem it always recommended is to control the moisture content of the wood properly. The wood moisture content should be as close as possible to the in the wood moisture content of the wood in the balancing with the air humidity in the area where furniture products will be used. To find out how much wood moisture content required it can be seen from the graph of wood moisture content vs. air humidity environment.
The humidity of course will vary for depend on the area. The humidity also changes according to the season. The best way to make wood furniture is to place the wood in the area where the furniture will be used for a year until the wood adapts with the environment. But of course this process is not economical for the furniture industry. The furniture manufacturer may be located in a certain area but he always need to be able to send his products to all over the world.

Here are the things that must be considered to reduce the wood crack problem.
  • Do adequate drying process in wood.
Make sure the wood or veneer is already dry enough before processed. The ideal moisture content is the balanced wood moisture content according with the humidity of the area where the furniture will be used. It may be rather difficult, but the wood moisture content maximum 12 % is usually enough for much area in the world. There are some areas that may have an extreme condition that need special wood m.c. More about the recommended wood m.c. can be viewed at our article: the moisture content in the woodworking industry.
  • Make a construction that can tolerate the possibility of movement on the connections and joints.
The wood movement is still highly possible happened on the furniture products. So we better  anticipate to the wood movement by adjusting the construction. If it is possible it is better to design the furniture in the shape and construction that give room is for the wood movement possibility. 
  • Do finishing process for both sides, especially for the wide and large surface. 
The finishing layer will reduce the porosity of the wood. The finished surface will less sensitive with the environment. The wood panel that finished only in the one side is not balanced and high risk of bending or cracking. It is always recommended to finish both sides of every wood panels. The back side doesn’t need to be finish as good as the front surface, 2 or 3 layer of clear coating is usually enough to balancing with the front side.
  • Control the moisture content since the beginning of process.
The moisture content of the wood should be correct from the beginning of process. The drying process after the furniture is built is always followed with the dimension changes. It will cause quality problems such as: crack, uneven surfaces, bent, unfit door, etc. 
Do the control of the moisture content in the beginning, check the moisture content of every pieces of wood before they are laminated, glued, machined or other processed. It will help to reduce the wasting time since of wood movement problems.  

 PSI MMETER2 Digital Readout Moisture Meter

Woodworking tools to make furniture

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