To examine the characteristics of French oak in detail, some 43 chemical compounds were measured in 24 air-seasoned samples from Troncais, Allier and Limousin; one sample from the Vosges area was also included.
Comparison of American, French and Eastern European air-seasoned oak
Figure 8 Principal Components Plot Showing the Similarity Between American, French and Eastern European Air-Seasoned Oak Samples.
Once the source of oak is decided, however, attention must be given to how the wood should be seasoned--in particular whether it should be air-seasoned or kiln-dried.
To begin to understand the differences between air-seasoned and kiln-dried oak, it is helpful to review the historical development of barrel production in the U.S.
Firstly, sections of early wood, late wood and medullary rays from a series of air-seasoned and kiln-dried samples were analyzed.
Principal Components Plot Comparing Unseasoned, Kiln-Dried and Air-Seasoned Oak.
The samples included pieces of the same tree which were divided into two pieces, one piece being kiln-dried and the other being air-seasoned. Air-seasoned samples were examined at seven, 12 and 18 months.
It can be seen that from the green, unseasoned wood the kiln-dried and air-seasoned follow different paths; indeed they are at right angles (in mathematical terms, orthogonal) to each other.
1992) had shown samples seasoned for longer than 18 months and for up to 72 months showed no significant changes: by 18 months the air-seasoned target had been reached.