Durability
A durable wood has the ability to resist decay in wet outdoor ground contact and a perishable wood species has the least resistance to decay. Because most wood pallets and packaging are expected to last only a couple of years, they are constructed of the least durable species available (the most perishable). However, it is important to note that any pallet and packaging timber species used commercially can easily last for 10 years if kept fairly dry for most of the time as wood is naturally very durable in dry environments. We often use the same species in house building and these species can last for hundreds of years without substantial change since biological deterioration is caused principally by water, insects and fungi. Some products, such as potato boxes, pool pallets and military packaging are expected to last years rather than months and it is essential that packaging makers in these fields understand the causes of decay in order to avoid disapointed customers.
50 year old redwood telephone pole
If decay starts, as it progresses timber steadily loses all strength and since most pallets and packaging are purchased entirely for their strength and protection capabilities this has to be allowed for in unprotected outdoor packing. Durability does not vary much between the timber species used in European pallets and packaging, but has become more important since for environmental reasons preservatives are now used less and less. The term perishability may be more relevant rather than durability because almost all the pallets and packaging species used in Europe are classed as perishable or non-durable. Durability of heartwood is rated species by species in EN 350-1: 1994: Durability of wood and wood-based products - natural durability of solid wood. For a summary of the major wood packaging species in this EN, download PalletLink Datasheet 78b.
Preservatives can raise the durability of a timber species from very low to very high. The photo above is a classic example of the efficiency of preservatives on low durability redwood used in transmission poles where the preservative (creosote) treated perishable sapwood in the outer part of the pole is still sound long after the more durable untreated heartwood has long since rotted away. However, the dominance of food and pharmaceuticals in the pallet using industry, plus environmental considerations, has reduced their use to practically nil in the wood packaging market. Other methods need to be used to increase pallet and packaging life where this is needed.
The Datasheets following explain the terminology and how decay, durability, perishability, dry-rot and wet rot are all related to moisture in wood or moisture in the air and how they affect pallets and packaging.
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31g Avoiding wood decay in potato storage boxes. (PDF 30kb)78b Natural Durability of Timber used in packaging. (PDF 27kb)81f Wood pallets stored at chilled temperatures (PDF 119kb)81h The causes of bluestain in packaging timber. (PDF 83kb)81m Dry rot - does it apply to wood pallets and packaging. (PDF 67kb)