We are generally aware that in woods and forests, fallen trees will decompose. Insects, birds and animals, as well as fungi, algae and bacteria, all participate in that process. Two silent partners in the process of decomposition are moisture and sunlight. Either too much water or too little water will weaken wood. Even in a protected household environment, prolonged exposure to high moisture content air, such as damp, misty, winter days or sticky, humid, summer days will help along the process of decay. Extremely dry air will cause shrinkage and cracking. Further, rapid changes from hot to cold, from damp to dry, create stresses which will, over time, weaken wood. Ultra violet light from the sun will damage wood by breaking down the cellular structure of the outer layers of the wood. In our homes the process of decay is usually very slow, even with unprotected wood. However, warping, twisting, shrinking, cracking and and even fading are all evidence that the process is taking place.
Wood Needs Protection:
Furniture has been described as functional art. It needs to be useful but we want it also to be beautiful and we further expect it to be durable. In order to preserve our investment in pieces of functional art, we need to protect them from whatever will cause them not to be durable. Most fundamentally, this means we need to protect them from extremes of moisture, rapid changes in moisture and from the harmful effects of sunlight. Hence the craft of furniture finishing.
Two Ways To Protect:
Finishing materials used to protect wood from extremes of moisture fall into two categories, finishes which penetrate the wood and finishes which form a coating over the wood. Oils such as tung and linseed have been used as penetrating finishes.Waxes and various natural resinous materials have been used to form coatings over the wood. Finishes which protect wood from sunlight have almost always included the introduction of earth pigments along with an oil or resin. With the addition of enough pigment, the finish becomes what we call paint.
Preserving wood is an important function of furniture finishes, but since furniture is functional art, creating something which pleases the eye is another demand placed upon furniture finishes. Most often this is done by choosing a finish which will accentuate the natural beauty of the wood. Penetrating finishes do the most to display the natural features of the wood to greatest advantage. However, penetrating finishes are not as durable or as resistant to damage as are finish coatings. External finish coatings also have the advantage of versatility in creating special effects to further intensify the aesthetic appeal of the functional art. Due to concerns regarding the health of the workers who apply these coatings and concerns regarding the purity of our common environment, many of the finishes used historically are no longer legal to apply without a special permit.
