Toronto - Shrinkage is a factor to be reckoned with in all wood construction. In simple terms, shrinkage is the contraction of wood as a result of a loss of moisture. When a tree is freshly cut, it has a high moisture content which is evident by its sappy nature and extreme weight.

    Presuming that wood is dried to a point where it is stable prior to its use (and that's not always a safe presumption), should additional problems be expected?

    The answer is yes. Wood can be brought to a point of relative stability, but the environment in which it is placed is not stable. Invariably wood will continue to lose moisture from years of being indoors. What is more significant is that wood will continue to change with seasons. Wood will gain or lose moisture according to the moisture content of the air. Summer provides high moisture, while winter means low moisture and contraction.     A piece of furniture purchased in a high-moisture area such as London, England and brought to a drier environment such as New York or Toronto often will start to fall apart through contraction.

    The degree of shrinkage varies with the age of the piece (how much it has pre-shrunk already), the type of wood, and how it was constructed. There is no mystery to some pieces falling apart.

    The move to lower humidity (often centrally heated houses) results in shrinkage. Stress to all the glue lines causes the piece to sometimes come unglued.

    The first rule of shrinkage is that all woods shrink across the grain. The second rule is that all wood will continue to shrink to some degree after being employed in furniture construction.     The third rule is that all wood will continue to expand and contract with changes in humidity no matter what you do to it (save shrink wrapping it in an air-tight plastic wrapper!).

    The last rule, to complicate matters, is that uneven absorption of moisture (one surface absorbing more than the other surface) will result in warpage. This last point is all too frequently illustrated with tabletops. A craftsman will finish the top surface of a table, for example, but rarely the underside. The finish on the top surface inhibits the absorption of moisture (the primary reason for using a finish) forcing greater absorption from the bottom. The consequence is a warped top leaf. This effect is known as cupping. Understanding and observing shrinkage is at the basis of authenticating antique furniture. Without shrinkage, a piece simply cannot be antique. A piece exhibiting shrinkage might not be unique but it must be old. In some cases, a combination of very well-seasoned wood and a stable climate will result in a minimum of shrinkage to a table and no splitting. But you are likely to encounter more split tops than not.

    Over the years when I have found harvest tables in barns, deserted houses, and old sheds, I have invariably had problems with shrinkage and splitting when the items are refinished and moved into a heated home or cottage. Tables on pedestal bases are less likely to split because the manner in which they are attached allows greater latitude for the movement of the wood.

    There are numerous examples of shrinkage. In an old schoolmaster's desk the cross member shrinks and leaves a shrinkage ridge where it is mortised into the 1eg post. With ladderback chairs the slat will shrink leaving a portion of the empty mortise showing. In addition, the glue holding the chair together will dry and crumble with temperature and moisture change. Everyone has experienced a chair coming apart.

    The important thing with shrinkage is the simple principal that it shrinks across the grain. The nailed blanket box will not change because all sides are continuous and they will shrink the same. After a hundred years or so each will have shrunk to approximately the same width. The key to shrinkage in this case will be the bottom of the box. Considering the bottom board is fixed at several points it will either have cracked or pulled away at one side.

    So, the next time your newly purchased antique shrinks in the winter, don't blame the dealer - check your heat!