The Country grade according to the regulations UNI EN 13489 (appendix B for the definition of the Free category) is to be consider ed a free category with the following features:
Iroko, Doussiè, Wenge: before and after the sanding, traces of concretions and silicon powders may show up: their colour varies from a whitish to a lemon yellow colour. After oxidation, in most cases they acquire the wood specie colour. Anyway, because the presence of this silicon powders is part of the nature of the wood, it can not be considered as defect and it can not be used for any kind of complain about the quality of the wood and the product.
The colours of the woods mainly depend on the wood specie. Each wood colour varies when exposed to light for a period of time (oxidation) . Each wood species has its own colour and texture. Each wood specie and supply show a different look depending on the area of origin. (Taken from UNI-EN 13226 regulation sect.5).
Teak: early colour differences during oxidation dim sensibly, until they become uniform in the definitive colour. Doussiè: during oxidation colour differences of some elements may increase in comparison with the whole lot.
Possible successive purchases of the same wood floor may have different shades compared to the original floor. This is due to the oxidation process that affects the wood after some time. Specifically in case of coloured finishes a change in colour may be evident; white finishes tend to turn yellow.