These questions are very important, as the answers have a direct bearing on the optimal treatment of timber. 

Sapwood is the soft, outer layers of a tree containing living cells, and can absorb chemical preservatives. Heartwood is the denser inner portion in which the cells have died. It provides structural support to the growing tree, and is mainly found in older trees. By its nature, heartwood is protected from most biological attack, and it cannot absorb preservatives. 

This means that the sapwood, alone, constitutes the treatable zone of your eucalyptus poles. 

Treaters need to know the “sapwood ratio” of their timber – the proportion of the total volume that is sapwood – in order to calculate the optimal strength of their CCA solution. However, the sapwood ratio is different in the various new eucalyptus hybrids that have been introduced in recent decades. 

These hybrids were introduced in a bid to cope with climactic changes, to ensure quicker growth of the trees, and to prevent biological attack. Interestingly, they were introduced for the pulp industry, which uses most of the wood grown in plantations, rather than the timber industry. 

The varying – but as yet undetermined – sapwood ratios of these new hybrids, is the cause of concern about whether the current South African specifications are adequate.  

In response to this uncertainty, the treatment industry in South Africa is undertaking an academic study to determine if the current specifications for eucalyptus poles are still relevant for the many new eucalyptus hybrids. 

The fact that the specifications are being reviewed in South Africa, prompts us to realise that the broader industry, in other African countries, should also be reviewing specifications. There are many specifications authorities in the various African countries, and we believe that in many cases, the suitability of these specs for the changing eucalyptus species has not been assessed. 

In the light of these realisations, Dolphin Bay has published another edition of Industry Note, to inform wood treaters of the potential hazards of neglecting the sapwood ratio of your eucalyptus poles, and to recommend a possible way to proceed. We look forward to sharing these views with our customers and the broader industry. 

The ultimate aim of our efforts is to help develop cutting-edge standards for the African wood treatment industry – standards which, we hope, will ultimately be incorporated into legislation. The sustainability of our industry depends on us getting it right.