Hardwoods

SPOTTED GUM (Lemon-Scented Gum)

Also applies to Iron Bark, Tallow Wood and Black Butt

Spotted Gum is a naturally dense greasy wood with a high extractives 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 (axe handles)
In these situations it was rare to coat the timber with anything other than an oil type preservative.
It has come to our attention that Spotted Gum is high on the list of timber types where early failures of coating systems are reported. Observed failures are mainly due to poor adhesion, the symptom being the coating coming off in small flakes or the coating completely disappearing.

Unfortunately, we have not been able to reproduce these results in any of our exposure testing.

After analyzing all the reports of short life of systems one frequent factor that emerged was the time of the year of application. Nearly all were in the summer months when the ambient temperature and just as importantly the surface temperature would have been very high. Because warm air temperature and hot surface cause rapid drying due to evaporation this can cause the product to thicken and dry before it can penetrate and adhere to these very dense surfaces.
Following temperature instructions on the label of the can is most important to longevity of product.

There are a number of other chemical factors we are investigating.

Based on our experience, we recommend it is best to coat Spotted Gum and similar timbers with a basic oil type system e.g.; Bio Oil or Quantec, after suitable cleaning.
These products are easy to apply with ease of re-application.

Surface of Spotted Gum magnified 50 times. Note uneven resinous surface.

Surface of Spotted Gum magnified 50 times.
Note uneven resinous surface.