PRESERVATIVE TREATMENT OF JAK (Artocarpus heterophyllus) SAPWOOD USING CCA and BORON PRESERVATIVES

Abstract

In Sri Lanka Jak timber is listed as a special class timber. Jak timber has high demand forconstruction and furniture. Jak heartwood is highly durable. However. sapwood issusceptible to borer attack. This study was conducted to determine the suitable andpractical treatment method for Jak sapwood to improve its durability Different aged 10trees of Jak (Artocarpus heterophyllus) were selected for the study. Sapwood samples andheartwood control samples were extracted from each tree.

Jak sapwood was treated by three methods: Boron (Cold) diffusion and Boron (Hot & Cold)open tank method using 25% boron solution and Pressure Impregnation Full-cell processusing 2.8% CCA (Copper Chrome Arsenate) solution. The treatability of different agedtrees was evaluated by measuring the preservative retention and depth of penetration.Effectiveness of the treatment was evaluated by percentage weight loss in field exposuretest.

According to the results, retention in CCA pressure treated samples was higher comparedwith boron diffusion methods. Boron (Hot & Cold) open tank method gave higher retentioncompared with boron (cold) method. Spot test showed full depth of penetration (100%) inboth boron treatments and 46% penetration in CCA pressure process.

In field exposure test, the highest weight loss was recorded in boron (Hot & Cold) treatedsamples and second weight loss was recorded in boron (Cold) treated samples. There wasno significant difference in the weight loss between two boron treatment methods. Weightloss of the CCA pressure treated samples was very small. Although full depth ofpenetration was not achieved with CCA pressure impregnation, it was found more effectivefor the preservation of Jak sapwood.

Based on the results, it is clear that Jak sapwood can be fully treated with boron diffusionmethods and effectively treated with eCA pressure impregnation method. Diffusionmethods using boron solution is recommended for the interior joinery and CCA pressureimpregnation is recommended to use 1ak sapwood in exterior construction activities.

However, sapwood of Jak showed other undesirable characters in terms of utilizationcompared with heartwood, density of sapwood was low, and shrinkage was higher.