Wood properties according to the wood finishing

From the first time when mankind knew furniture until today, wood is used as the main material to make furniture. Wood is the product of provide many advantages. Tree is a renewable material. It can be obtained either  from forests or plantations and with good management the source will always be available. Wood also has unique and distinctive beauty that can not be replaced with other materials. Then it is very reasonable if until now wood is still the main raw material for making furniture.
But to handle the wood properly we need to understanding the wood and its characters. The wood is product from trees which are living beings. Wood has many species that each has different characters and properties.  Wood characters are determined by how the tree alive and growing during his lifetime. The wood with the same species will have the similar character. But since the tree is the living creature, then there will be some variation in properties according to the condition of the weather, soil and place where the tree was living. The with the same type may have different characters when coming from different places.
The characters of the wood must  be recognized by the people who work in the furniture finishing industry. The basic characters of the wood are actually a great value that must be maximized for furniture to make a valuable product. One task of finishing is to maximize the uniqueness of the raw materials that have been there to make valuable furniture. There are at least 4 properties of wood that need to be considered in the finishing process that are: basic color, grains and pores, porosity, and hardness. They are all must be considered by the finishing people, because it will determine the appropriate finishing process for the wood.

wood color

• Wood base color

Each type of wood will have different basic colors, such as mahogany wood has smoothly red color, teak wood has a dark brown color, and oak has brown-green color, pine has a yellow white color, etc. For finishing with a solid color or an opaque color, the color of the wood will not affect the finished color because the color finishing is completely determined by the color of the stain used. But for the transparent color, then color of the wood base will greatly affect the final color, because the final color is the combination of the basic colors of the wood and the wood stain used. The wood with light color (white color), can be finished with more color choice. The dark stains can be used to coloring the wood to make dark color. If the light color is chosen, then we can apply the light stain.
For the wood which has dark color then the options for finishing color is quite limited, there is no stain can lighten the basic color. The finish color is limited from the wood base color to the darker. When we choose the finishing color we have to consider the basic color of surface that already in there. The color of the finishing we choose cannot be lighter than the basic color of the substrate. If the final color desired is lighter than the basic color of the wood, the he bleaching process is needed. Bleaching is chemically process to lighten and whiten the wood. The bleaching process is tough, costly and dangerous so it should be avoided as much as possible. Therefore, the selection of the final finish color according to the base color of the furniture substrates is the best way. Use the wood with the light base color if the light finish color is needed; use the dark wood for the dark finish color. The right selection of the substrate will ease the process of finishing and reduce the finishing cost.

• Wood pores and grains

Each type of wood has a different pattern of grains and pores. Grain is the result of the cambium developed during the growth of the tree. It is mainly determined by the species of the tree and how he lives. Some types of wood have with very strong and clear grain character such as: teak, mahogany, rosewood, walnut, etc. While some other wood have vaguely and soft grain character such as: aghatis, sengon, ash, etc. 
Wood pores are holes that are found in the wood. These pores are also formed when the wood grew during his lifetime and depend to the wood species. There are several types of wood have the big pores such as oak, mindi, teak, etc. While other types of wood only have small and shallow pores such as: maple, ash, beach, etc. But the character of the wood is also depend on how the tree was living. Then the pores and grains pattern of the wood are also depend to the place where the wood come from. Sometime we find the wood with same species have difference grain and pores character. For example we can find some oak wood with smaller and less pores, while at the other time we may find the oak with big and more pores because he comes from different place.
The pattern of wood grains and pores actually is one of the uniqueness and great value of wood that should be enhanced in the finishing process. The finishing should adapt and follow to the pattern of grains and pores in the wood and maximized his performance. The wood with a strong character grains should be proper finish to maximize its unique character, including the grains and pores pattern.

• Porosity 

Porosity of wood is the wood's ability to absorb liquids. There some wood that has high porosity such as: sengon wood, pine, aghatis, etc. They will absorb more finishing materials in the finishing process. This wood will need more coating materials to achieve the smooth surface and film built. Meanwhile at the stain application the wood with a high porosity will absorb more stain and tend to generate the dirty or dark color. To avoid this problem we can use the thin and sprayed lightly in many times. For some types of wood that is really soft, we may need to do the sealer or glue sizing (see our other article : glue sizing for wood finishing).
There also some wood that has very low porosity such as hard mahogany, walnut, rosewood, etc. They are less in absorbing finishing materials and sometimes make the finishing materials difficult to wet the wood. For this type’s wood we also need some modification in finishing process. We can use the slow drying stain to let the stain wet and soak the wood and coloring the pores and grain to maximize the wood finishing color.

• Hardness of wood

Wood also has different hardness depending on the species of the wood. The hardness of the wood is also need to be understood since it will determine the proper process of sanding. The hard wood has the stiff wood fibers that is easy to be cut in the wood sanding. The hardwood is easier to be sanded to produce the even and smooth surface. Meanwhile the soft wood is usually more difficult to be sanded because the wood has more elastic wood fibers. The fibers tend to "lay down" in the sanding process. The softwood need more sanding step. We need to do sanding gradually with less jump grade sandpaper from the beginning to the end. We also need to replace the sandpaper soon after it is blunt and cannot cut the wood fibers
Imperfect sanding will result to the uneven absorption of the stain applied on. It lead to a blotchy or spotty color in the finishing. To overcome this problem for some soft wood we can use wash coat application before the sanding process. The wash coat or sealer will wet and wraps the wood fibers and stiffen them when they dry. Then the stiff and hard wood fibers are easily to be cut in the sanding process to produce an even and smooth surface. See our finishing article : sealer sizing