This site provides notes describing methods of drying wood so as to produce dried products of good quality.
Note that these notes do not address the production of dry wood for the purpose of burning but relate to the drying of (mainly) sawn wood intended for use in construction and the fabrication of furniture and similar wooden products.
The notes begin by addressing the reasons for drying wood: one very important reason for reducing the moisture content in wood is to ensure that when a wooden product is put into service the environment where the product is installed does not cause the product to shrink or swell unduly. Another good reason for drying wood is to avoid fungal degradation of the wood. A number of other reasons for drying wood will also be explained.
After giving some important fundamental concepts and definitions which need to be understood for optimal and efficient wood drying, the notes then describe the factors which control wood drying. Some of the controllable factors relate to the environment where the wood is dried (such as the temperature and humidity of the air), but to dry wood efficiently and so produce wood of optimum quality the internal structure of the wood must be appreciated. Consequently the notes also include an introduction to the structures of hardwoods and softwoods and their effects on the drying process.
A major part of this site describe the best practices when drying wood by air seasoning in timber yards and in drying kilns.
Tips for successful air seasoning of timber are given and the expected rates of drying, and, importantly, the limitations of air seasoning in producing dry wood are described. The optimal layout of an area where wood can be dried in the open air (a timber "drying yard") is described - this being critical to drying wood efficiently, as are the design and arrangement of the stacks in the drying yard.
There follows a thorough description of the kiln drying wood, where the need to provide a sequence of optimal temperatures, relative humidities and air circulation rates is described and the concept of a “Kiln Schedule” is explained. Different types of kiln drying equipment are described. A comparison of the advantages and disadvantages of drying wood in kilns compared to air seasoning: this information, and more, is covered in air drying of wood.
The use dehumidifiers to dry wood is also described as are high temperature wood drying methods and the use of solar kilns to dry wood.
The notes end with descriptions of the various defects in dried timber which can arise and how these defects can be avoided. So, for example, the causes and prevention of spring, twist and checking are explained, as is the serious defect of case hardening of wood. The final page of these notes explains how case hardening of wood can be avoided and mention is made of a number of other defects which can arise when drying wood.