Product potential of paulownia timber

Summary

FPC Timber Technology assessed the properties of timber from three 10-y-old paulownia (Paulownia fortunei) logs from Queensland. The logs were regular in form with some taper. No end checking was evident prior to sawing. Growth stresses were minimal and the logs were sawn without difficulty using a horizontal bandsaw mill to produce straight backsawn and quartersawn timber. Mean green sawn recovery was 55% of log volume. Milling waste that was stored green for eight weeks developed sap stain.

The sawn timber was dried in a heat-and-vent kiln over 45 d, showing good drying quality. Stability in service should be high, although unit shrinkage was not assessed.

The timber was straight-grained with a moderately coarse even texture, a straw yellow to pale brown colour and lightly figured. Grading to the FIFWA (1992) Industry Standard for Seasoned, Sawn and Skip-Dressed WA Hardwoods gave 51.8% dry recovery (not dressed) of Prime Grade timber. Mean volumetric shrinkage was estimated as 6.0%. Dressing to the standard dimensions specified in the FIFWA Standard would give dry dressed graded recovery of 38.2%. Air-dry density was 260 kg m⁻³; hardness measured using a modified Janka method was only 0.5 kN.

The timber was ripped, crosscut, planed, sanded and bored without undue difficulty, notwithstanding a need for sharp tools and high cutter speeds. Router cuts were characterised by feathery edges that were improved by sanding. The timber achieved 100% wood failure in PVA glue tests and should therefore glue well. The test panels were fine sanded and finished to a high standard using a clear finish, but staining was less successful.

These results conform with those in previous literature, and indicate that paulownia timber is suitable for wall and ceiling linings, claddings (if treated), decorative mouldings, picture frames, timber blinds, doors and windows. The timber also seems well suited as a substrate in veneered products including doors and tabletops, and as a general carcass material in low-stress situations where weight savings may result from its use.

Keywords:

• seasoning
• wood properties
• shrinkage
• wood density
• working properties
• wood utilization
• Paulownia fortunei