Juglans regia

Juglans regia L. – Common walnut

group: 	SEMI-RING-POROUS HARDWOODS

Macroscopic structure of wood

heartwood/sapwood: 	heartwood

description: 	narrow sapwood (1–3 cm), greyish white; heartwood grey, greyish brown to greyish black (greyish violet – Black walnut); heartwood has irregular shape; dark vertical streaks (dark brown to black)

rings: 	slightly distinct boundary between rings; indistinct boundary between early wood and late wood in rings

vessels	macropores in whole ring (X – holes, R, T – fine grooves)

rays: 	numerous ray flack, visible only in R

texture: 	flatsawn (T), radial figure (R) and burl (T); very decorative wood

other: 	burl veneers are very valuable

Microscopic structure of wood

brief overview: 	Rays 1–5, HomG; macrovessels, tyloses

ring: 	invisible boundary between early and late wood within ring	X

vessel types and arrangements: 	only macrovessels (diameter of macrovessels goes down within a ring); microvessels solitary or in radial multiples (up to 4)	X

type of vessel perforation: 	simple	R

tyloses: 	numerous especially in heartwood	X, R, T

rays: 	homogeneous	R, T

width of rays	1–5	T, (X)

apotracheal parenchyma: 	marginal, diffuse-in-aggregates	X

paratracheal parenchyma: 	scanty	X

tracheids in basic tissue: 	vascular, vasicentric, fibre tracheids	R, T

other: 	crystals in ray cells

Wood properties

density: 	moderate heavy

ρ 0: 	660 kg/m3

ρ 12-15: 	700 kg/m3

ρ green: 	1000 kg/m3

shrinkage: 	medium

- volumetric (βV): 	12,9 %

- radial (βR): 	5,4 %

- tangential (βT): 	7,5 %

ultimate strength in compression ||: 	72 MPa

ultimate strength in bending: 	147 MPa

ultimate strength in tension ||: 	100 MPa

hardness: 	moderate hard

Janka's hardness: 	72 MPa

technological properties: 	no problem with working and finishing, it's necessary slowly drying (formation of crack) resistance: 	heartwood rated as moderate resistant to decay, sapwood rated as slightly or non-resistant to decay

Wood utilization

valuable for sliced veneers (especially burls), furniture, woodcarving, marquetry, wood haberdashery and imitation jewellery, turning work, picture frames and hunting rifle butts

References