Proceedings e report - Firenze University Press

WOOD SCIENCE FOR CONSERVATION OF CULTURAL HERITAGE
Keylwerth (1951) noted for the European species an average anisotropy of 0.61 (Sesbou, 1981). This
strong transverse anisotropy is one of the main causes of distortions resulting from wood drying.
3.3. Basic density
The average value found Y= 639 kg/m 3 is typical of this hardwood species. It presents a coefficient of
variation accepted for wood (7%). The loss of density of 4% by reconditioning is also a good indicator
of the phenomenon of collapse.
Correlations between specimens at the tree level
The correlation between basic density and partial L shrinkage is not significant at the 5% level. The L
shrinkage remains low and has little influence on the V shrinkage. Concerning R and T directions, the
correlation between basic density and radial shrinkage is not significant at the 5% level. However, the
correlation (r =- 0582 ***) between basic density and shrinkage with T collapse is highly significant
(Fig. 6). The regression equation is as follows:
RTS (%) =-0.0497Y + 39.992 with R 2 = 0.339 (10)
The basic density is significantly negatively correlated to the V collapse (Fig.7) with r =- 0.488 **.
The regression equation is as follows
RVS (%) =-0.0571Y + 48.403 with R 2 = 0.238 (11)
The obtained trend curves are consistent with Sesbou (1981) results: the higher the density, the lower
the shrinkage, confirming that the phenomenon of collapse is less pronounced for the densest woods.
The woods most affected by collapse are those with a medium density.
Tangential shrinkage (%)
Volumétric shrinkage (%)
20,00
15,00
10,00
5,00
RTS= -0,0497Y + 39,992
R 2 = 0,3391
335
r=-0,582***
0,00
500 550 600 650 700 750
Infradensity (g/dm 3 )
Fig. 5. Relationship between basic density and T partial shrinkage
25,00
20,00
15,00
10,00
5,00
Ρς Σ(%) = −0,0571Ψ + 48,403
Ρ 2 = 0,2384
r=-0,488**
0,00
500 550 600 650 700 750
Infradensity (g/dm 3 )
Fig. 6. Relationship between basic density and V partial shrinkage
The correlation between density and transverse anisotropy is positive with r = 0.475**. The regression
equation is as follows:
RRS / RTS = 0.0018Y – 0.6859. with R 2 = 0.226 (12)
The higher the basicdensity, the lower the anisotropy.