American Walnut

American Walnut

Origin: North America

Nomenclature:

• Polish: orzech czarny, orzech amerykański
• English: American walnut
• French: noyer noir d'Amerique, noyer noir, noyer d'Amerique
• German: Americanischer Nessebaum, Schwarznuss, Schwarze Walnuss
• names used in other countries: In the USA- American black Walnut, eastern black walnut, black walut, burbank walut, ekstern walut, Wirginia walut, gunwood, in Czech Republic - oresak cerny, in Italy - noce nero, in Croatia - crni orach, morsi orah, in Spain - nogal negro americano

Availability
26 mm – KD – SE edged – FAS/F1F grade
28 mm – KD – SE edged – FAS PRIME grade
52 mm – KD – SE edged – FAS/F1F grade
52 mm – KD – SE edged – FAS PRIME grade

Occurrence:

The homeland of the black walnut is North America. It covers the eastern and central parts of the continent from southern Ontario to northeast Florida, and in the west extends as far as Texas. These trees are mainly associated with lowland areas. This species likes deep, permeable soils and usually occupies areas along rivers where it grows in larger clusters. In drier areas it occurs singly as an admixture of other species. It is a light-loving plant that can withstand temperature drops as low as -25°C. Black walnut was brought to Europe in the 17th century.

Tree habit:

Black walnut in North America grows to a height of 30-35 m. Growing compactly, the tree produces a relatively small crown, but under other conditions it becomes elaborate and domed. The trunks are covered with grey-black bark with deep furrows. Larger trees reach a diameter at breast height of over 1.5 m.

Structure type:

deciduous, diffuse-vascular - large vessels visible to the naked eye.

Sapwood:

It is creamy white to grey-brown and quite narrow, usually clearly demarcated from heartwood zone. 

Heartwood:

It ranges in colour from light brown to chocolate brown with a purple shade and often contains darker streaks. The intensity of heartwood colouring depends on the growth conditions of the wood (it is higher in the south and decreases towards the northern limit of the range). Steaming the wood causes the colour to darken.

Fragrance:

The dried wood does not emit any characteristic odour.

Pattern:

Enriched by large vessels. They are visible on the cross-section as lighter spots and on the longitudinal cross-section as small furrows slightly darker than the surrounding wood tissue. Fine medullary rays, macroscopically only appear on radial section. The poorly defined and somewhat wavy annual increments can best be seen in cross-section. The wood does not show a stratified structure. 

Typical defects:

Uneven colour intensity.

Physical properties of American Walnut:

According to a six-grade scale, it is a moderately heavy wood (Class III). The average air-dry density of the wood is 640 kg/m³. According to the Monin classification, this species belongs to the medium shrinkage wood category – volume shrinkage is approximately 12.7 % on average. Anisotropy of shrinkage has a low value of -1.4.

Mechanical properties of American Walnut:

The generally straight-fibred wood of black walnut has favourable strength conditions. Average compressive strength along the fibres – 53 MPa, and static bending strength – over 90 MPa. The average hardness of the wood tested, determined by the Janka method on the cross-section, is 46 MPa, and the elastic modulus determined in static bending ranges from 11.0 to 13.5 GPa.

Durability:

Heartwood is classified as moderately durable against the destructive effects of fungi. According to the standard, it is Class III. At the same time, it is a difficult or very difficult material to impregnate with impregnating agents. 

Drying:

Relatively easy. 

Working:

Wood easy to work with by hand and machine. Thanks to the homogeneous structure of the annual increments and the straight fibre arrangement, good surface quality without breakouts is achieved during cutting, drilling, milling and turning.

Sanding:

This wood sands and polishes well.

Joining:

Black walnut wood gives strong joints with metal fasteners (does not break when nails are driven) and bonds well. When using alkaline adhesives, permanent staining can occur (reaction with tannins). Polyurethane-epoxy, polyurethane and hybrid adhesives should be used.

Finishing:

A properly well-prepared surface accepts paints and varnishes well. Normally, this wood is covered with sealed coatings of varnish.

Intended use:

A long-established and well-known parquet material, it has been used in coffered and inlaid floors. At present, walnut wood is mainly available on the market in the form of boards and slats as well as layered elements. In the latter, the walnut wood forms the upper wear layer, determining the aesthetics and appearance of the floor. This wood is recommended for rooms with low to medium traffic.
Other uses – black walnut wood is among the most valued species due to its ease of working and high aesthetic qualities. As a noble material, it has found use in furniture, carpentry and artistic products. It is used to make joinery and finishes for exclusive residential interiors and means of transport (yachts, cars, carriages, aeroplanes). It is also a material used in woodworking, including woodcarving products and musical instruments. Historically, black walnut was used for the mass production of aircraft propellers, sewing machines and firearm butts. There is a reason why one of the American names for the wood in question is "gunwood".

Similar species:

Other nut species, notably: walnut from Europe, grey walnut from North America and Bolivian walnut from South America, as well as mansonia from Africa. Mansonia is distinguished by the presence of stratified construction.

Notes:

Wood with high variability and intensity of colour depending on the habitat (origin).

Trivia:

In Poland, black walnut is planted as an ornamental tree in parks and botanical gardens. One of the oldest and most magnificent specimens grows on the grounds of the Warsaw University of Life Sciences. The tree probably grew from a walnut tree planted in 1822 and given to Julian Ursyn Niemcewicz by US President George Washington. Black walnut, compared to walnut, has a much harder seed shell – not every nut cracker can handle it, but this does not translate into wood properties (the two species are almost identical in terms of properties).

• Mechanical properties: can be worked very easily. Exhibits good nailing and screwdriving properties and adheres well. Accepts stains and paints very well, and an exceptionally good surface finish can be achieved by polishing.
• Modulus of elasticity: 11.6 GPa
• Volumetric shrinkage: 10.2%
• Specific gravity: 610 kg/m3 (12%)
• Durability: species resistant to destructive fungal attack
• Dry wood pests: resistant – risk limited to sapwood penetration
• Protections: class 1-2 – accepts preservatives