Also applies to Iron Bark, Tallow Wood and Black Butt
Spotted Gum is a naturally dense greasy wood with a high extractive content that can give rise to problems when gluing or coating. Spotted Gum and related timber types have traditionally been used for heavy engineering construction, piles, poles, heavy decking on piers and high impact tool handles (e.g. axe handles). In these situations it was rare to coat the timber with anything other than an oil type preservative.
Spotted Gum is high on the list of timber where early failure of coating systems are reported. Observed failures are mainly due to poor adhesion of the substrate, which includes flaking or the coating completely disappearing off the substrate.
After analysing reports of short life of systems; one frequent factor that emerged was the time of year of application. Nearly all reported adhesion problems were in the summer months when the ambient temperature and surface temperature would have been very high. Warm air temperature and hot surface temperatures cause rapid drying due to evaporation – this can lead the product to thicken and dry before it can penetrate and adhere to these very dense surfaces.
Based on our experience, we recommend it is best to coat Spotted Gum and similar timbers with a basic oil system such as QUANTEC, after suitable cleaning of the surface. For more information refer to our technical bulletins or contact technical service on 1300 132 202.