The Efficacy of a Borate and Penetrating Oil Preservative Combination for the Conservation of Exterior Wood

This study evaluates aqueous diffusible borates in combination with a penetrating oil and a nano-size iron oxide and zinc oxide based wood preservative system for cypress (Taxodium distichum) and western redcedar (Thuja plicata). The objectives are as follows, 1) To test the efficacy and performance of the coating to retain the borates through accelerated weathering test (QUV) on exterior wood; 2) To gauge the durability of the preservative combination and how nano metallic particles (iron oxide and zinc oxide) impact weathering behavior; 3) To characterize modes of failure via substrate morphology change (SEM), pigment loss and color change (spectrophotometer); 4) To apply this data to help formulate a practical preservative system for the conservation of exterior wooden cultural heritage. The results of the accelerated weathering program (QUV) and borate indicator show that the penetrating oil has the ability to prevent diffusible borate from leaching. SEM imaging analysis and photo documentation of samples change in different intervals illustrate that the surface morphology change and nano metal material has good UV blocking performance as part of the system.