The Structural Conservation of Panel Paintings

Beechcan usually be identified on sight by its easily visible rays.

On transverse surfaces, the largest of the rays form conspicuous light

radial lines recognized quickly, especially with a hand lens (Fig. 17). On

tangential panel surfaces the uniformly scattered larger rays are character-

istic; on radial surfaces the rays produce a striking ray fleck of darker ray

tissue against lighter background tissue. Beech is properly classified as a

diffuse-porous wood, with uniformly small pores evenly distributed across

most of the growth ring, although an apparent latewood zone of fewer

pores terminates each growth ring. Beech may be confused with plane

(Platanusspp.), which also has large rays. In plane, however, the rays are

uniformly large and appear more crowded on tangential surfaces. Confu-

sion is easily resolved by microscopic examination of a tangential section:

in plane the rays rarely exceed 15 seriate; in beech the widest rays are up

to 20–25 seriate, with many cells of very small diameter (Fig. 27f ).

Alder(Alnus spp.) is light reddish brown, diffuse porous, and fine

textured. It may be recognized on sight, however, by the occasional pres-

ence of large, conspicuous, oak-sized rays (Fig. 18). These rays are rela-

tively few in number and may be inches apart—thus, small samples of the

I  W  P P 35

a bc

d ef

Figure 27a–f
Tangential sections showing examples of ray-
cell size and shape as well as ray seriation in
various hardwoods: (a) uniseriate rays with
flattened cells in poplar (Populussp.); (b) multi-
seriate rays in mahogany (Swieteniasp.);
(c)multiseriate rays with flattened to oval
cells in lime (Tiliasp.); (d) multiseriate rays
(up to 4–5 seriate) with rounded cells in soft
maple (Acersp.); (e) multiseriate rays (up to
8–9 seriate) with rounded cells in hard maple
(Acersp.); and (f ) a portion of a large multi-
seriate ray with variable-sized cells in beech
(Fagussp.).

ab

Figure 28a, b
Radial sections of (a) poplar (Populussp.)
showing the large ray-vessel pits in the mar-
ginal rows of procumbent ray cells in contact
with a vessel element; and (b) willow (Salixsp.)
showing the large ray-vessel pits in the mar-
ginal rows of upright ray cells.