Surface Investigation of Photo-Degraded Wood by Colour Monitoring, Infrared Spectroscopy, and Hyperspectral Imaging

Table 1

Averages of the chromatic coordinates at different times of exposure in Solar Box for poplar samples. M-ANOVA test shows highly significant differences of the colorimetric parameters at different exposure times. Different letters indicate statistical differences (Tukey test, alfa = 0.01).

Time (h)	𝐿^∗	HSD	𝑎^∗	HSD	𝑏^∗	HSD
0	84.3	a	2.0	b, c	16.8	a
1	83.7	b	1.4	a	16.7	a
2	83.6	b	1.3	a	17.1	b
3	83.4	b, c	1.4	a	17.8	c
4	83.8	a, b	1.3	a	19.7	d
5	83.3	b, c	1.4	a	19.6	d
6	83.0	c, d	1.5	a	19.7	d
7	82.6	d, e	1.9	b	20.7	e
8	82.0	e, f	2.0	b, c	20.6	e
9	81.7	f	2.0	b, c, d	21.1	f
10	82.0	f	2.1	b, c, d	21.2	f
11	81.9	f	2.1	c, d	21.6	g
12	81.9	f	2.1	d	22.7	h
24	80.9	g	2.6	e	25.3	i
48	80.0	h	3.4	f	27.6	l
72	79.7	h	4.0	g	29.9	n
96	78.3	i	4.5	h	29.4	m
120	78.1	i	4.8	i	29.9	n
144	77.9	i	5.2	l	30.3	o
168	77.7	i	5.7	m	31.4	p
216	76.4	l	7.1	n	33.1	r
312	72.7	m	8.9	o	33.1	r
408	71.7	n	8.7	p	32.2	q
504	71.6	n	9.5	q	33.3	r

∗Statistically significant.