Persoz hardness: a useful property to study performance of exterior wood coatings

Improving the durability of exterior coatings is essential for the use and development of wood as a building material. In Europe, performances of wood coatings are mainly estimated through visual assessments of panels exposed to weathering. The aim of this work was to investigate the Persoz pendulum as a simple tool to gain information on hardness and mechanical properties of exterior wood coatings. The influence of the substrate and the coating thickness has been studied to figure out the limits of the test method. Through a comparison with tensile tests performed on free films, Persoz pendulum was found to be relevant as a simple tool to estimate mechanical properties of the coating film. Finally, Persoz hardness was assessed on several coatings exposed to 4032 h of artificial weathering. Results have shown that the pendulum hardness test is a useful method to study wood coatings performances for outdoors.