PAULOWNIA CHARACTERISTICS

Lightweight

Paulownia is about 2/3 the weight of the lightest commercial wood grown. Average cubic foot weight varies between 15 to 19.

This falls between Balsa wood and Poplar. Paulownia is 1/3 the weight of Oak (44 lbs p/cubic ft) and half the weight of Pine (30 lbs p/cubic ft).

The specific gravity of Paulownia ranges between 0.23 to 0.30 (23 to 30% of the density of water).

Strength

Balsa has been considered to have the highest strength to weight ratios of any wood in the world. Paulownia has been tested to have a higher strength to weight ratio than Balsa. Auburn University, Alabama tested the strength of 18 lb p/cubic ft. against Balsa, with an average weight of 10 lbs p/cubic foot. (See Table 1)

Table 1

Strength of modus rupture (psi)

     Balsa..........2800

     Paulownia....5740

 Source Dr. R.C. Tang, Auburn University

Some Balsa core material is sliced at 3/8 inch with end-grained material. Paulownia could be cut at 3/16 and offer approximately the same strength and weight. Paulownia offers a space saving benefit, being cut half as thick. There is also a significant cost savings because half as much material would need to be purchased. When considering the large amount of epoxy that Balsa soaks up, Paulownia gains an even larger weight advantage.

Paulownia holds nails and screws well and does not require pilot holes to be drilled. In fact both yellow poplar and white pine have proven to split before Paulownia. Flat head screws can be driven flush with the surface. Plantation grown Paulownia is mostly knot free.

Workability

Paulownia has been widely used in the orient for fine furniture, musical instruments, carvings and decorative finishes for over 1000 years. It can be peeled for veneer in 1/16 inch thickness and has even been sliced at 1/32 inch. Intricate patterns can be cut with a jig saw or band saw without splitting easily. Paulownia has been a favourite for many carvers throughout the world. Furniture, doors and windows can be made with close tolerances. All normal finishing materials can be applied and it bonds well with glue.

Stability

Air-drying takes as little as 30 days. Boards can be kiln dried at high temperatures in as little as 24 hours to 10% to 12% moisture content with no warping. Reported shrinkage from green to oven dry is only 2.2% radial and 4.0% tangential.

Paulownia remains stable during changes in humidity and experiences little shrinkage or expansion compared to most other woods. It is highly durable and resists decay under non-ground contact conditions. The wood is insect resistant.

Conductivity

Paulownia is a very good insulator. Paulownia log homes are said to have twice the R factor as pine or oak logs. This temperature resistance serves to give the wood a high fire resistance. Ignition temperature is approximately 400 deg. C. which is almost twice many conventional hard and soft woods.

Attractiveness

Paulownias are fast growing trees that have a light blond appearance, similar to White Ash.

It stains well with a variety of colours and can be made to mimic other woods.

Once planed a silky lustre is revealed. The feel is also very silky.