Cedar, Western red

A few acid woods, such as oak, chestnut and Western red cedar, accelerate surface weathering of aluminium, but do not usually give rise to serious attack . Timber preservatives containing soluble copper compounds should be avoided creosote and zinc napthenate are satisfactory preservatives for wood in contact with aluminium. 

Zinc in contact with wood Zinc is not generally affected by contact with seasoned wood, but oak and, more particularly, western red cedar can prove corrosive, and waters from these timbers should not drain onto zinc surfaces. Exudations from knots in unseasoned soft woods can also affect zinc while the timber is drying out. Care should be exercised when using zinc or galvanised steel in contact with preservative or fire-retardant-treated timber. Solvent-based preservatives are normally not corrosive to zinc but water-based preservatives, such as salt formulated copper-chrome-arsenic (CCA), can accelerate the rate of corrosion of zinc under moist conditions. Such preservatives are formulated from copper sulphate and sodium dichromate and when the copper chromium and arsenic are absorbed into the timber sodium sulphate remains free and under moist conditions provides an electrolyte for corrosion of the zinc. Flame retardants are frequently based on halogens which are hygroscopic and can be aggressive to zinc (see also Section 18.10). 

Smith, R. S., Johnson, E. L. and Cserjesi, A. J., Corrosion of Zinc-Coated Nails Used with Preservative-Treated Western Red Cedar Shakes in Service. Document No. IRG/WP/ 3197, International Research Group on Wood Preservation, Stockholm (1982)... 

Certain LMW agents will cause OA via a poorly defined mechanism. Only about 20% of workers with OA to toluene diisocyanate (TDI) have IgE detectable to TDI indicating that IgE antibody may be more an indicator of exposure rather than a mediator of the disease [10], Similar data exist for workers with asthma caused by plicatic acid from western red cedar [11], The inability to detect IgE antibody in the majority of these workers may be based in technical issues such as the nature of the chemical-protein... 

Tse, K.S., Chan, H., and Chan-Yeung, M., Specific IgE antibodies in workers with occupational asthma due to western red cedar, Clin Allergy, 12, 249, 1982. 

Chan-Yeung, M., Giclas, PC., and Henson, P.M., Activation of complement by plicatic acid, the chemical compound responsible for asthma due to western red cedar (Thuja plicata), J. Allergy Clin Immunol., 65, 333, 1980. 

One way to avoid the use of any preservative is to use wood that is naturally resistant to decay. The heartwood of more naturally rot-resistant species, such as oak, can be used untreated. Other woods that last well without treatment are larch, which will last about 10 years in contact with the soil, or up to 20 years if not in contact with soil Western red cedar, which will give service for about 20 years and sweet chestnut, traditionally used for fence palings and posts. Untreated pine lasts for about five years. Well-seasoned wood that has been allowed to dry out evenly is more expensive than greenwood (freshly cut undried wood), but in its favor, it tends to last longer and can be less prone to distortion as it weathers. 

Fujita M, Gang DR, Davin LB et al (1999) Recombinant pinoresinol-lariciresinol reductases from western red cedar Thuja plicatd) catalyze opposite enantiospecific conversions. J Biol Chem 274 618-627... 

Primary irritant dermatitis caused by wood contact consists of erythema and blistering, which may be accompanied by erosions and secondary infections. Irritant chemicals typically are found in the bark or the sap of the outer part of the tree. Therefore, loggers and persons involved in initial wood processing are most affected. In most reports of contact dermatitis, hardwoods of tropical origin have been implicated, although other woods, including pine, spruce, western red cedar, elm, and alder, have been cited. 

Extensive studies have been done on a clearly defined asthma syndrome produced by exposure to western red cedar. ° Plicatic acid has been identified as the etiologic agent. The western red cedar asthma syndrome includes rhinitis, conjunctivitis, wheezing, cough, and nocturnal attacks of breathlessness characterized by a precipitous decline in FEVi. There is no apparent relation between skin sensitivity and respiratory changes. No precipitating IgG antibodies are found in the serum of sensitized individuals, and circulating IgE antibodies are present in about one-third of affected individuals. 

Chan-Yeung M, et al Occupational asthma and rhinitis due to Western red cedar (Thuja plicata). Am Rev Respir Dis 108 1094-1102, 1973... 

Figure 1 Changes in color of outdoor weathered western red cedar, redwood, southern yellow pine, and Douglas fir in the USA. (From Ref. 16.)...

Figure 2 Changes in color of outdoor weathered radiata pine and western red cedar in New Zealand.

Perhaps the most extensive area of research in simple pretreatment systems to enhance the weathering properties of wood has involved application of inorganic salt solutions. Much of the early work in this field was undertaken at the U.S. Forest Products Laboratory in Madison, Wisconsin and was aimed at improving the performance of transparent finishes. Black [25] described an experimental chromate-based wood finish and Black and Mraz [26] discovered that both acid and ammoniacal-copper chromate treatments significantly improved the performance of clear finishes on western red cedar, redwood (Sequoia sempervirens), and Douglas fir plywood. Later research [27] demon-... 

Kim, M.K., Jeon, J.H., Davin, L.B., Lewis, N.G. (2002a) Monolignol radical-radical coupling networks in western red cedar and Arabidopsis and their evolutionary implications. Phytochemistry, 61,311-22. 

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