" " wisno wood furniture finishing: Wood grain.

Friday, October 26, 2012

Wood grain.

Wood grain is the uniqueness of the wood that is not replaceable. The wood grain is visible as a dark and light color variation, the strips with a particular color and texture at the surface of the wood pieces. Wood grain is formed in the timber when the tree grows; its pattern and character depend to the wood species and the condition when the tree was alive. The wood grows and enlarges its size by built a cambium, a thin layer of living cells. At the inside pat of the cambium there is the sapwood, it is the cambium with old cells. The sap wood is a young wood cell which carries water, minerals, and plant sugars between the roots and the leaves. At the center is the heartwood; it is the dead cells that no longer serve any purpose except to support the tree. The heartwood is the wood that is used in the woodworking industry.
As the cambium grows, it generates two types of wood cells. Most of these are long, narrow longitudinal cells that align with the axis of the trunk, limb, or root. The cambium also produces a smaller number of ray cells that line up in rays extending out from the pith, to the radial direction. These are what give the wood its grain. The cambium grows rapidly at the beginning of the growing season and slows down at the cold season. This cycle produces distinctive growth ring, that visible at the wood as the wood grain. 


wood anatomy

The type of wood grain.
The wood grain pattern and character is unique, depend to the wood species. Each wood species will have a special pattern of the grain. As a material from living things, the wood grain is also highly affected by the condition of the tree when he was alive; the soil, and the climate.
The wood grain looked is also depend to the method to cut the tree. At least there are three method to cut the tree that give different grain pattern. 
 wood cutting

  • end grain. The wood grain is obtained when the wood is cut across the grain.
Wood is cut in the transverse direction of the grain will result in the holes of the hollow piece of wood grains. The resulting pieces will be rough with open pores from the grain hollow with the low strength of the wood pieces.
  • Tangential directions grain. The grain is obtained when the wood is cut according to the grain direction. 
This cutting method will give the maximum benefit to the wood, the maximum wood strength and the beauty of the wood grain. There are many cutting method of spitting the wood; flat sawn, rift sawn and quarter sawn. Each cutting method will give different grain appearance, if the thin sheet wood (veneer is made), then more variation can be obtained.( see our previous article : wood veneer slicing )

Things to be consider about the wood grain. 

 
Wood grain is the natural beauty of the wood that should be maximized in the product designing and finishing. With proper finishing, the wood grain can produce the attractive wood products with beautiful appearance.
But instead of its beauty, the wood grain character could lead to the finishing (appearance) problem is it is not well managed.  Here are the things that must be considered according to the wood grains.

  • Color and pattern of grain.
The wood grain could change the wood appearance.  The “color” of the wood may be looked different when it is viewed with the different direction. For some type of wood that has strong grain character such as: mahogany, teak or the different could be so big, until we can see the “flip off”. It is actually the main beauty of the wood, but sometime it could be awfully when it doesn’t, manage well. The wood could be looked ugly when the grain is not well match. Then when we deal with the wood pieces that are combined to make big panel, we need to consider about the wood grain pattern. Make sure we match the grain pattered when we united the wood pieces.
  • Texture of the grain.
The wood grain on some wood species is also shown by the texture at the wood surface. Some wood species has a soft texture such as: mahogany, pine, maple etc.. However, some wood has rough grain texture such as: mindi or oak. The grain texture can be enhanced by the proper finishing. We can use glaze or stain to fill in the grain to get the contrast looked. Some finishing models even use the wire brushing to open and enlarged the wood grain. But to make finishing with flat and even surface, then the grain texture is problem. We may need to apply filler or putty to close the grain.
  • Wood pores.
Wood pores are tiny hollows in the wood; it exists as holes at the wood surface. As the grain texture, the wood pores is also can be maximized to make the attractive looked finish. We can apply glaze or stain to enhance the wood pores.  
But to finishing with a plain color and close pore, the presence of the pores can be distracting. The pores will leave undesirable open at the finish. Some type of wood pores is lead to the hungry looked, bubble and pinhole problem.  The application of wood filler could be needed to handle this problem.
  • Porosity.
Wood grain pattern may be emerged with distinction porosity at the wood surface. The difference in porosity could be large so that it can generate variation to the stain absorption in the finishing process. The big variation could make the uneven or blotchy color. The risk is higher when the stain is applied by wiping, brushing or dipping. The application of wood conditioner may be needed to avoid this problem.

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