The tropical woods
Apuleia leiocarpa
,
Couratari stellata
,
Mezilaurus itauba
and
Simarouba amara
were selected to examine the effect of the presence of the extractives in the color variation and in the
photodecomposition process of their surfaces. Samples with and without extractives were submitted to cycles
of ultraviolet radiation (350 nm) and immersion in water until totalizing 2,000 hours of irradiation and 400
hours of water leaching. Changings in the natural wood colors were monitored by diffuse reflectance
spectroscopy. Samples of
Simarouba amara and
Couratari stellata with extractives content of 2% or less
showed color variation with time of treatment almost similar to the samples without extractives. The
abnormal resistance of
Couratari stellata to color changing can not be attributed to extractives. For the
Apuleia leiocarpa and
Mezilaurus itauba woods, the presence of 11,7% and 7,42% of extractives
compounds, respectively, accelerated the color variation rate. Analysis of the color variation indicated that
the extractives, in this case, acted by intensifying the natural wood color. Additionally, it was verified that
Couratari stellata was the more resistant wood to color variation in this studied group of woods, followed by
Apuleia leiocarpa,
Simarouba amara and
Mezilaurus itauba, all with extractives.
