Article The Colour of Tropical Influenced by Brown Rot

Zuzana Vidholdová * and Ladislav Reinprecht Technical University in Zvolen, Faculty of Sciences and Technology, T. G. Masaryka 24, Zvolen, SK 96001, Slovakia; [email protected] * Correspondence: [email protected]; Tel.: +421-45-520-6389

 Received: 26 February 2019; Accepted: 2 April 2019; Published: 10 April 2019 

Abstract: Interesting aesthetic properties of tropical woods, like surface texture and colour, are rarely impaired due to weathering, rotting and other degradation processes. This study analyses the colour of 21 tropical woods before and after six weeks of intentional attack by the brown-rot fungus Coniophora puteana. The CIEL*a*b* colour system was applied for measuring the lightness, redness and yellowness, and from these parameters the tone angle and colour saturation were calculated. Lighter tropical woods tended to appear a less and a more yellow, and had a greater hue tone angle. However, for the original woods was not found dependence between the lightness and colour saturation. Tropical woods at attack by C. puteana lost a weight from 0.08% to 6.48%. The lightest and moderately light species—like okoumé, iroko, ovengol and sapelli—significantly darkened, while the darkest species—wengé and ipé—significantly lightened. The majority of tropical woods obtained a brighter shade of yellow, typically wengé, okoumé and gum, while some of them also a brighter shade of , typically sapelli, padouk and macaranduba. C. puteana specifically affected the hue tone angle and colour saturation of tested tropical woods, but without an apparent changing the tendency of these colour parameters to lightness. The total colour difference of tested tropical * * woods significantly increased in connection with changes of their lightness (∆E ab = 5.92 − 0.50·∆L ; R2 = 0.37), but it was not influenced by the red and yellow tint changes, and weight losses.

Keywords: tropical woods; brown rot; Coniophora puteana; colour; CIEL*a*b* system

1. Introduction The surface appearance of wood is often evaluated by examining its texture, roughness, and colour [1–3]. The colour of an individual wood species is predetermined by the type and amount of extractives, by the surface roughness and moisture, and by the direction of light irradiation [4]. The CIE 1976 L*a*b* colour system classifies the temperate and tropical wood species into the positive octant with the lightness (L*) from 20 to 90, the redness index (+ a*) from 0 to 20, and the yellowness index (+ b*) from 10 to 30 [1,5]. The CIE 1976 L*a*b* colour system also allows visualisation * of the cylindrical parameters of wood, the colour saturation—chromaticity (C ab) and the hue tone angle (hab)[6]. The tropical wood species occupy a much greater portion of the colour space in comparison with temperate (for example European) species [7,8]. Within a defined wood species, the colour variations can be influenced by more factors, mainly by its chemical and anatomical structure [9] and specific genetic parameters [10], and also by environmental conditions at growth [11,12], atmospheric effects at exposure in exteriors or interiors [13,14], and biodeterioration processes [15–17]. Wooden products having a higher moisture content—usually above 20%–30%—are no rarely damaged by biodeterioration processes in presence of wood decaying fungi, staining fungi, moulds, or bacteria.

Forests 2019, 10, 322; doi:10.3390/f10040322 www.mdpi.com/journal/forests Forests 2019, 10, 322 2 of 14

Generally, brown-rot fungi cause firstly yellowing and gradually browning of woods in a connection with decomposition of whiter hemicelluloses and cellulose, while darker lignin is less evidently damaged [18,19]. Wood extractives, which give to different wood species a characteristic colour, are specifically resistant to individual species of brown-rot fungi [20–22]. Therefore, the accidental or deliberate exposures of wood products to brown-rot fungi can lead to typical changes in their colour and aesthetic parameters. The rotting of damp wooden products is common not only outdoors, but also inside of buildings. In interiors, the rotting of wood is first of all caused by brown-rot fungi [23–25]. The genus Coniophora comprises about 20 species frequently occurring in buildings. Gabriel and Švec [26] listed the species abundance of seven indoor wood decay basidiomycetes reported in Europe, when the brown-rot fungi Serpula lacrymans and Coniophora puteana (C. puteana) were most frequent. C. puteana causes—already in the early period of wood attack—a disruption of linkages between hemicelluloses and lignin, decomposition of polysaccharides, while lignin is oxidative modified and partly damaged [27]. Rot of wood with C. puteana is not usually homogenous and it’s specific parts can be more damaged [15]. In the literature, it is also noted that wood-inhabiting fungi are able add colour to wood due to a pigment residues left by fungi in wood (called as spalting) [17,28–34]. Spalting occurs in growing tree in form of zone lines formation or pigmentation. Also bleaching is marked as kinds of wood spalting [17,29,31]. Bleaching is caused by the breakdown of coloured lignin from the wood cell wall, generally by fungi classified as white-rotting, which results in a lightening of the natural wood colour and structural integrity of the wood. A lightening in colour can also be due to a build-up of white mycelium [18,20,35]. Wood with zone lines (thin and winding lines of dark melanin) are formed due to inter- or intra- fungal antagonism for example a pairing of the white-rot fungi Trametes versicolor/Bjerkadera adusta or by solitary isolates of Xylaria polymorpha ascomycete that causes soft rot [31]. Also, the brown-rot fungus Fistulina hepatica stains and some other woods from light gold, yellow brown to reddish brown shades [36,37]. Pigment-type spalting fungi are a select group of soft-rotting ascomycetes with extracellular pigments production into wood, for example fungi from genera Chlorocibolia, Ceratocystis, Ophiostoma, Scytalidium and others [32,33]. Pigment penetration into wood depends on moisture content, the digestive capabilities of the fungus, the permeability of the wood structure, differences between heartwood and sapwood, and the type of pigment produced [29]. Mold fungi, such as Trichoderma spp., are not considered to be spalting fungi, as their hyphae do not colonize the wood internally and they do not produce the enzymes necessary to digest the wood cell wall components. From several tropical woods are manufactured various products for interiors, for example, furniture, flooring, stairs, windows, doors, claddings or structural elements—using usually massive, glued timbers, veneers or plywood [38]. For more of these products, both strength and aesthetic are important. The interesting aesthetic and specific colours of the individual tropical wood species, existing in the natural state as well as in the primarily fungal-pigmented state, can be changed or even worsened at additional rotting processes. In interiors, the degree and range of rotting is influenced mainly by: (1) the natural durability of wood to decaying fungi (e.g., [39] classifies woods into five classes of durability), and (2) the enough moisture of wood above 20%, depending on presence of condensed, capillary, plumbing or rain water. The aim of this study was to determine the colour changes of 21 tropical woods when exposed to the brown-rot fungus C. puteana, which can cause an important deterioration of wood products in the interiors of buildings.

2. Materials and Methods

2.1. Woods and Specimens Twenty-one tropical woods, in a form of naturally dried and conditioned boards with a moisture content of 13 ± 2.5%, was bought from the trading company JAF Holz, Ltd., Slovakia (Table1). Forests 2019, 10, 322 3 of 14

Table 1. Tropical wood species used in the experiment.

Family Species Species Density at MC 12% (kg·m−3) Common “Literature” Scientific Name “Experiment” Name 1) [40] Handroanthus serratifolius Bignoniaceae Ipé 960–1100 968 (26) (Vahl) S.O.Grose 3) 4) Aucoumea klaineana Burseraceae Okoumé 370–560 566 (27) Pierre 2) Weinmannia trichosperma Cunoniaceae Tineo 570–650 646 (31) Cav. Dark red curtisii Dyer ex Dipterocarpaceae 590–890 592 (10) meranti King 2) Yellow balau 5) Shorea laevis Ridl. 2) 900–1100 925 (55) Macassar Ebenaceae Diospyros celebica Bakh. 2) 1100–1200 1 013 (82) ebony Doussié Afzelia bipindensis Harms 2) 750–950 889 (18) Amburana cearensis A. C. Cerejeira 550–650 651 (10) Sm. 2) demeusei J. Bubinga 830–950 830 (13) Léonard Ovengol J. Léonard 2) 700–910 755 (27) Merbau Intsia bijuga O. Ktze. 2) 830–900 837 (50) Santos Machaerium scleroxylon 900–1000 904 (6) rosewood Tul. 2) Microberlinia brazzavillensis Zebrano 700–850 718 (23) Chev. 2) laurentii De Wengé 810–950 823 (37) Wild. 2) Padouk Pterocarpus soyauxii Taub. 650–850 647 (37) Meliaceae Sapelli 510–750 631 (38) cylindricum Sprague 2) Moraceae Iroko C. C. Berg 2) 550–850 551 (16) Eucalyptus diversicolor Myrtaceae Karri 800–870 804 (30) F. Muell. Blue gum Eucalyptus globulus Labill. 720–770 760 (59) Maçaranduba Sapotaceae 6) Manilkara bidenta A. Chev. 900–1000 916 (19) Makoré Tieghemella heckelii Pierre 2) 530–720 570 (25) Notes: 1) by Association Technique Internationale des Bois Tropicaux (ATIBT) in France; 2) registered in The IUCN Red List of Threatened Species™ [41]; 3) name by EN 350 [39]; 4) previous name by [40] was Tabebuia serratifolia; 5) its other name is Bangkirai; 6) its other name is Massaranduba; Mean values of experimental densities are from 16 specimens (4 of those were used in this experiment) and standard deviations are in italic and parentheses.

From the heart-zone of each wood species were prepared and tested four specimens 25 mm × 25 mm × 3 mm (longitudinal × radial × tangential)—without biological damage, knots or other defects. Before the fungal attack, the top surfaces of specimens were sanded along fibres using 240-grit sandpaper. Subsequently, the specimens were conditioned on a moisture content of 12 ± 1%, weighted with an accuracy of 0.001 g, sterilized with 30 W germicidal lamp (Chirana, Slovakia) at a temperature of 22 ± 2 ◦C per 20 min for each side, and finally their top surfaces submitted in sterilized room to colour analyses (point 2.3). After fungal attack (point 2.2), the specimens were carefully cleaned from surface fungal mycelia, slowly dried in a laboratory, conditioned on a moisture content of 12 ± 1%, weighted with an accuracy of 0.001 g, the top surfaces sanded along fibres with 240-grit sandpaper, and finally the top surfaces again submitted to colour analyses (point 2.3). At sanding of the top surfaces of tested specimens, performed before and after fungal attack, in both cases the thickness of specimens declined about approximately 10 micrometers. Forests 2019, 10, x FOR PEER REVIEW 4 of 14

After fungal attack (point 2.2), the specimens were carefully cleaned from surface fungal mycelia, slowly dried in a laboratory, conditioned on a moisture content of 12 ± 1%, weighted with an accuracy of 0.001 g, the top surfaces sanded along fibres with 240-grit sandpaper, and finally the top surfaces again submitted to colour analyses (point 2.3). ForestsAt2019 sanding, 10, 322 of the top surfaces of tested specimens, performed before and after fungal attack,4 ofin 14 both cases the thickness of specimens declined about approximately 10 micrometers.

2.2.2.2. Fungal Fungal Attack Attack of ofWoods Woods TheThe specimens specimens of of tropical tropical woods woods were were exposed exposed to to the the brown-rot brown-rot fungus fungus ConiophoraConiophora puteana puteana (Schumacher(Schumacher ex ex Freist) Freist) Karsten, Karsten, strain strain BAM BAM Ebw. Ebw. 15 (Bundesanttalt 15 (Bundesanttalt für Materialforshung für Materialforshung und – prüfung,und—prüfung, Berlin) in Berlin) glass inPetri glass dishes Petri with dishes a diameter with a diameter of 100 mm. of 100 Two mm. replicates Two replicates of the same of the wood same specieswood were species placed were into placed one intodish one on plastic dish on mats plastic under mats which under a fungal which amycelium fungal mycelium was already was grown already ongrown an autoclave on an autoclave sterilized sterilizedand solidified and 3–4 solidified mm thick 3–4 layer mm thickof 4.5 layerwt.% ofmalt 4.5 agar wt.% medium malt agar (HiMedia, medium ◦ Ltd.,(HiMedia, India). Fungal Ltd., India). attacks Fungal lasted attacks6 weeks lasted at a temperature 6 weeks at of a temperature24 ± 2 °C and of a 24relative± 2 humidityC and a relative of 90 ± humidity5%. of 90 ± 5%. TheThe weight weight loss loss m∆ m(%)(%) of of specimens specimens was was calculated calculated from from their their weights weights in in conditioned conditioned state state beforebefore and and after after fungal attack. attack. This This method method may may have have caused caused some some inaccuracies inaccuracies in ∆m in(due m to (due sorption to sorptionhysteresis hysteresis and differential and differential water sorptionwater sorption by healthy by healthy and rotten and rotten woods), woods), but it but was it preferredwas preferred to the tomethod the method evaluating evaluating specimens specimens in absolute in absolute dry state dry when state colourwhen colour change change could be could manifested be manifested at drying ◦ attemperature drying temperature of 103 C. of 103 °C.

2.3. Colour Analyses of Woods 2.3. Colour Analyses of Woods TheThe colour colour analyses analyses were were performed performed for for each each specimen specimen before before and and after after fungal fungal attack attack on on the the sanded top surfaces (point 2.1) in the same four places (Figure1). The colour measurements were sanded top surfaces (point 2.1) in the same four places (Figure 1). The colour measurements◦ were performedperformed with with the the Color Color Reader Reader CR-10 CR-10 (Konica (Konica Minolta, Minolta, Japan), Japan), having having a CIE a CIE 10° 10 standardstandard observer, observer, CIECIE standard standard illuminate illuminate D65, D65, sensor sensor head head with with a diameter a diameter of 8 of mm 8 mm (i.e.(i.e., the measuring the measuring area areawas was50 2 mm502 mm), and), a and detector a detector with with6 silicon 6 silicon photocells. photocells.

Figure 1. The same four places on the top surface of specimen in which colour measurements were Figureperformed 1. The in same its original four places and fungal-attackedon the top surface state. of specimen in which colour measurements were performed in its original and fungal-attacked state. The colourimetric parameters of each specimen were analysed according to the CIE 1976 L*a*b* colourThe system.colourimetric A larger parameters value of L of*, aeach*, or bspecimen* means awere lighter, analysed redder, according or yellower to colour,the CIE respectively. 1976 L*a*b* * * * * colour Basedsystem. on A the largerL , a value, and ofb Lcolour*, a*, or coordinates, b* means a lighter, following redder, the colour or yellower saturation—chromacity colour, respectively.C ab andBased the hue on tonethe L angle*, a*, andhab wereb* colour calculated coordinates, according following to the [the42] colour by Equations saturation—chromacity (1) and (2): C*ab and the hue tone angle hab were calculated according to the [42] by equations 1 and 2: ∗ p ∗2 ∗2 Cab = a + b , (1) 2 2 퐶∗ = 푎∗ + 푏∗ (1) 푎푏 −1 ∗ ∗ , hab = tan (b /a ), (2) ∗ ∗−1 ∗ ∗∗ From the relative colour changesℎ푎푏∆=L , tan∆a ,( and푏 /푎∆b) ,, namely differences between colour(2) coordinates of the fungal-attacked and the original wood specimens, the total colour difference    *From the relative colour changes L , a , and b , namely differences between colour ∆E ab was calculated by Equation (3) [42]: coordinates of the fungal-attacked and the original wood specimens, the total colour difference E*ab was calculated by equation 3 [42]: ∗ p ∗2 ∗2 ∗2 ∆Eab = ∆L + ∆a + ∆b , (3)

* * * Selected colourimetric parameters of tropical woods determined in the original state (a , b ,C ab, * * * hab), as well as in the fungal-attacked state (a F, b F,C ab F, hab F), were finally analysed in relation to ∗ ∗ their lightness (L or L F) by linear correlations using Equation (4):

Colourimetric parameter = A + B·L∗, (4) Forests 2019, 10, x FOR PEER REVIEW 5 of 14 Forests 2019, 10, x FOR PEER REVIEW 5 of 14 Forests 2019, 10, x FOR PEER REVIEW 5 of 14 Forests 2019, 10, x FOR PEER REVIEW 5 of 14 Forests 2019, 10, x FOR PEER REVIEW 5 of 14 Forests 2019, 10, x FOR PEER REVIEW 5 of 14 Forests 2019, 10, x FOR PEER REVIEW ∗ ∗2 ∗2 ∗2 5 of 14 Forests 2019, 10, x FOR PEER REVIEW 퐸푎푏∗ = 퐿∗2 + 푎∗2 + 푏∗2 , 5 of(3) 14 Forests 2019, 10, x FOR PEER REVIEW 퐸푎푏∗ = 퐿∗2 + 푎∗2 + 푏∗2 5 of(3) 14 Forests 2019, 10, x FOR PEER REVIEW 퐸푎푏∗ = 퐿∗2 + 푎 ∗2 + 푏 ∗2 , 5 of(3) 14 퐸푎푏∗ = 퐿∗2 + 푎∗2 + 푏∗2 , (3) 퐸푎푏∗ = 퐿∗2 + 푎∗2 + 푏∗2 , * * (3)*ab Selected colourimetric parameters퐸푎푏∗ of= tropical 퐿∗2 woods+ 푎 ∗determined2 + 푏∗2 ,in the original state (a*, b*, C(3)* , Selected colourimetric parameters퐸∗ of= tropical 퐿∗2 woods+ 푎∗ determined2 + 푏∗2 ,in the original state (a*, b*, C(3)*ab, Selected colourimetric parameters푎푏∗ of tropical* * woods* determined ,in the original state (a *, b *, C(3)*ab, hab), asSelected well as colourimetricin the fungal-attacked parameters퐸 state푎푏 of= (tropical a F, b퐿F,∗ 2C woods+ab F, h푎ab∗ Fdetermined2), +were 푏 finally∗2 , in analysedthe original in relationstate (a ,to b ,their C ab, hab), asSelected well as colourimetric in the fungal-attacked parameters퐸 state푎푏∗ of= (tropical a*F, b*퐿F,∗ 2C woods*+ab F, h푎ab∗ Fdetermined2), +were 푏 finally∗2 in analysedthe original in relationstate (a* ,to b* ,their C(3)*ab, ab   퐸 = *F *퐿F *+ab F푎ab F + 푏 , * * (3)* h ), asSelected well as colourimetric in theF fungal-attacked parameters state푎푏 of (tropicala * , b * , C woods* , h determined), were finally ,in analysedthe original in relationstate (a ,to b ,their C ab, lightnesshab), asSelected well (L asor colourimetric inL the) by fungal-attacked linear parameters correlations state of using (tropicala*F, b equation*F, C woods*ab F, h 4:ab Fdetermined ), were finally in theanalysed original in relationstate (a*, tob* ,their C*ab, lightnesshab), asSelected well (L asor colourimetric in L theF) by fungal-attacked linear parameters correlations state of using (tropicala*F, b equation*F, C woods*ab F, h ab4: Fdetermined ), were finally in theanalysed original in relationstate (a*, tob* ,their C*ab, lightnesshab), as well (L asor in L theF) by fungal-attacked linear correlations state using (a F, b equationF, C ab F, h ab4: F ), were finally analysed in relation* to* their*ab hlightnessab), asSelected well (L asor colourimetric in L theF) by fungal-attacked linear parameters correlations state of using (tropicala*F, b *equationF, C woods*ab F, h ab4: Fdetermined ), were finally in theanalysed original∗ in relationstate (a*, tob* ,their C* , hlightnessab), asSelected well (L asor colourimetric in L theF) by fungal-attacked linear parameters correlations퐶표푙표푢푟푖푚푒푡푟푖푐 state of using (tropicala*F, b equation*F, C푝푎푟푎푚푒푡푒푟 woods*ab F, h ab4: Fdetermined ), were= finally퐴 + in퐵 theanalysed∙ 퐿 original∗ in relationstate (a , to b (4),their C ab, hlightnessab), as well (L asor in L theF) by fungal-attacked linear correlations 퐶표푙표푢푟푖푚푒푡푟푖푐 state using (a*F, b equation*F, C푝푎푟푎푚푒푡푒푟*ab F, h ab4: F ), were= finally퐴 + 퐵 analysed∙ 퐿∗ , in relation to (4)their hlightnessab), as well (L asor in L theF) by fungal-attacked linear correlations 퐶표푙표푢푟푖푚푒푡푟푖푐 state using (a*F, b equation*F, C푝푎푟푎푚푒푡푒푟*ab F, h ab4: F ), were= finally퐴 + 퐵 analysed∙ 퐿∗ , in relation to (4)their lightness (Lor LF) by linear correlations 퐶표푙표푢푟푖푚푒푡푟푖푐 using equation 푝푎푟푎푚푒푡푒푟 4: = 퐴 + 퐵 ∙ 퐿∗, (4) lightness (Lor LF) by linear correlations 퐶표푙표푢푟푖푚푒푡푟푖푐 using equation 푝푎푟푎푚푒푡푒푟 4: = 퐴 + 퐵 *∙ 퐿∗ , (4) Equation 4 wasF used as well as for searching relations between the ΔE ab  and , the relative colour lightness (L or L ) by linear correlations 퐶표푙표푢푟푖푚푒푡푟푖푐 using equation 푝푎푟푎푚푒푡푒푟 4: = 퐴 + 퐵 ∙*ab퐿∗, (4) Equation 4 was used as well퐶표푙표푢푟푖푚푒푡푟푖푐 as for searching relations푝푎푟푎푚푒푡푒푟 between= 퐴 the+ ΔE퐵 *∙ 퐿 ∗ and the relative colour(4) Equation  4 was used as well 퐶표푙표푢푟푖푚푒푡푟푖푐 as for searching relations푝푎푟푎푚푒푡푒푟 between= 퐴 the+ ΔE퐵 ∙*ab퐿 ∗ and , the relative colour ForestschangesEquation2019 , 10L,, 322 a4 ,was b ,used and asthe well weight as for loss searching m, respectively. relations between the ΔE*ab  ,and the relative colour5(4) of 14 changesEquation L,  4a was, b ,used and asthe well weight 퐶표푙표푢푟푖푚푒푡푟푖푐 as for loss searching m, respectively. relations푝푎푟푎푚푒푡푒푟 between= 퐴 the+ ΔE퐵 ∙ab퐿 ∗ and , the relative colour(4) changesEquation L ,  4a was, b ,used and asthe well weight퐶표푙표푢푟푖푚푒푡푟푖푐 as for loss searching m, respectively. relations푝푎푟푎푚푒푡푒푟 between= 퐴 the* +* ΔE퐵 ∙*ab퐿 * and the relative colour(4) Conversion    of average value of the colourimetric coordinates L , a and* b ,of the fungal-attacked changesEquation L , 4a was, b used, and asthe well weight as for loss searching m, respectively. relations between the* * ΔE*ab * and the relative colour changesEquationConversion L,  4a was, ofb average used, and asthe valuewell weight as of for the loss searching colourimetric m, respectively. relations coordinates between L the*, a* ΔEandab b* andof the the fungal-attacked relative colour changesConversion L, a, ofb average, and the value weight of the loss colourimetric m, respectively. coordinates L *, a * and* b * of the fungal-attacked and theEquationConversion original 4 waswood of average used specimens as valuewell as wasof for the generated searching colourimetric their relations colourcoordinates between (Pantone) L the, a ΔE swatch.and*ab b and of the the fungal-attacked relative colour andchanges theEquationConversion original L,  4a was, wood ofb average used, and specimens asthe valuewell weight as wasof for the loss generated searching colourimetric m, respectively. their relations colourcoordinates between (Pantone) L the*, a* ΔEswatch.andab b* andof* the ∗the fungal-attacked relative colour andchanges theEquationConversion original L, a (4) , wood of wasb average, and usedspecimens the value as weight well wasof asthe loss generated for colourimetric  searchingm, respectively. their relations colourcoordinates (Pantone) between L*, a* swatch.and the ∆b*E of theand fungal-attacked the relative changesand theThe original tL-test, a  statistically ,wood b, and specimens the analysed weight was loss thegenerated  colourm, respectively. their changes colour of (Pantone) individual* * swatch. tropical* ab woods due to the changesand theTheConversion original tL-test, a statistically , wood of∗b average, and specimens∗ the ∗ analysedvalue weight wasof the loss thegenerated colourimetric  colourm, respectively. their changes colourcoordinates of (Pantone) individual L*, a* swatch.and tropical b* of the woods fungal-attacked due to the colourand theTheConversion changes original t-test ∆ statistically woodLof ,average∆a specimens, ∆b analysedvalue, and wasof the the the weightgenerated colourimetric colour loss their changes∆m, colour respectively.coordinates of (Pantone) individual L*, a* swatch.and tropical b* of the woods fungal-attacked due to the brown-rotand theConversionThe original t -testfungus statistically woodof C. average puteana. specimens value analysed wasof the thegenerated colourimetric colour their changes colourcoordinates of (Pantone) individual L*, a* swatch.and tropical b* of the woods fungal-attacked due to the andbrown-rot theConversionConversionThe original t -testfungus statistically wood ofof C. averageaverage puteana. specimens valuevalue analysed ofwasof thethe thegenerated colourimetriccolourimetric colour their changes coordinatescolourcoordinates of (Pantone) individualL L*,, aa* andswatch.and tropical bb* of the woods fungal-attacked due to the brown-rotandbrown-rot theThe original t -test fungusfungus statistically wood C.C. puteana.puteana. specimens analysed was thegenerated colour their changes colour of (Pantone) individual swatch. tropical woods due to the andbrown-rot theThe original t -testfungus statistically wood C. puteana. specimens analysed was thegenerated colour their changes colour of (Pantone) individual swatch. tropical woods due to the and3.brown-rot Results theThe original t -testandfungus Discussion statistically wood C. puteana. specimens analysed was thegenerated colour their changes colour of (Pantone) individual swatch. tropical woods due to the brown-rot3. ResultsThe t -testandfungus Discussion statistically C. puteana. analysed the colour changes of individual tropical woods due to the 3.brown-rot ResultsThe t -test andfungus Discussion statistically C. puteana. analysed the colour changes of individual tropical woods due to the brown-rot3. Results andfungus Discussion C. puteana. brown-rot3.1.3. Results Colour fungusandof Original DiscussionC. puteana. Tropical Woods 3.3.1. Results Colour andof Original Discussion Tropical Woods 3.1.3. Results Colour andof Original Discussion Tropical Woods 3.3.1. Results ColourTable andof 2 Original documentsDiscussion Tropical colour Woods characteristics of 21 tropical woods in the original state—a 3.3.1. Results ColourTable andof 2 Original documents Discussion Tropical colour Woods characteristics of 21 tropical woods in the original state—a 3.1. ColourTable of 2 Original documents Tropical colour Woods characteristics of 21 tropical woods in the* * original* *ab state—aab 3.1.visualisation ColourTable of 2 Original (colour documents andTropical surface colour Woods structure), characteristics and the of colourimetric 21 tropical parameters woods in L the*, a *,original b*, C* and state—a h . 3.1.visualisation ColourTable of 2 Original(colour documents andTropical surface colour Woods structure), characteristics and the of colourimetric 21 tropical parameters woods in L the*, a *, original b*, C*ab and state—a hab. visualisationTable 2 (colour documents and surface colour structure), characteristics and the of colourimetric 21 tropical parameters woods in L the, a , original b , C ab and state—a hab. 3.1.3.1.visualisation Colour of Original(colour and Tropical surface WoodsWoods structure), and the colourimetric parameters L*, a*, b*, C*ab and hab. visualisationTable 2 (colour documents and surface colour structure), characteristics and the of colourimetric 21 tropical parameters woods in L the*, a *, original b*, C*ab and state—a hab. Table 2 documents colour characteristics of 21 tropical woods in the* * original* *ab state—aab visualisationTable 2 (colour documentsTable and 2. Visualisations surface colour structure), characteristics and colorimetric and the of colourimetric parameters 21 tropical of parameters21 woods tropical in woods. L the*, a *,original b*, C* and state—a h . visualisationTableTable2 documents 2 (colour documentsTable and colour2. Visualisations surface colour characteristics structure), characteristics and colorimetric ofand 21 the tropical of colourimetric parameters 21 woods tropical of in parameters21woods the tropical original in woods. L the state—a*, a *,original b*, C visualisation*ab and state—a hab. visualisation (colourTable and 2. Visualisationssurface structure), and colorimetric and the colourimetric parameters of parameters21 tropical woods. L*, a*, b*, C*ab and hab. visualisation (colourTable and 2. Visualisationssurface structure), and colorimetric and the colourimetric parameters of* parameters21* tropical* * woods. L , a , b , C ab and hab. (colourvisualisation and surface (colourTable structure), and 2. Visualisationssurface and structure), the and colourimetric colorimetric and the colourimetric parameters parameters Lof ,parameters21 a ,tropical b ,C woods.Colour andL*, a*h, b*., C*ab Hueand tonehab. Table 2. VisualisationsLightness and colorimetric Redness parameters Yellowness of 21 tropical ab woods.Colour ab Hue tone Wood species Table Visual 2. Visualisations Lightness and colorimetric Redness parameters Yellowness of 21 tropical saturation woods.Colour Hueangle tone Wood species Table Visual 2. Visualisations Lightness and* colorimetric Redness *parameters Yellowness of 21* tropical saturation woods.Colour Hueangle tone Table 2. VisualisationsL and* colorimetric+a *parameters of+ b21* tropical woods.Colour* Hue tone Wood species Visual LightnessL Redness+a Yellowness+b saturationColourC ab Hueangleh abtone Wood species Table Visual 2.2. Visualisations LightnessL andand* colorimetriccolorimetric Redness+a *parametersparameters Yellowness ofof+b 2121* tropicaltropical saturation woods.woods.* angle Wood species Visual LightnessL* Redness+a* Yellowness+b* saturationColourC*ab Hueangleh abtone Wood species Visual LightnessL* Redness+a* Yellowness+b* saturationColourC *ab Hueangleh abtone Wood species Visual LightnessL* Redness+a* Yellowness+b* saturationColourC*ab Hueangleh abtone Lightness42.59* Redness8.87* Yellowness16.46* Colour18.70C*ab Hue61.66h abtone WoodIpé species Visual 42.59L* 8.87+a* 16.46+b* Coloursaturation18.70C ab Hue Toneangle61.66hab WoodWood species Visual LightnessLightness42.59L RednessRedness8.87+a YellownessYellowness16.46+b saturation18.70*ab angle61.66ab WoodIpé species Visual Visual (0.79)* (0.55)* (1.01)* Saturationsaturation(2.59)C* Angleangle(1.22)h Ipé (0.79)42.59*L* (0.55)8.87+*a* (1.01)16.46+*b* (2.59)18.70C*ab (1.22)61.66hab SpeciesIpé (0.79)42.59LL +(0.55)a8.87+a +(1.01)16.46b+b *(2.59)18.70C ab (1.22)61.66hab Ipé 42.59 8.87 16.46 C18.70C*ab h 61.66hab Ipé (0.79)(0.79)42.59 (0.55)(0.55)8.87 (1.01)(1.01)16.46 (2.59)(2.59)18.70ab ab(1.22)(1.22)61.66 Ipé (0.79)75.3642.59 (0.55)5.618.87 (1.01)16.8916.46 (2.59)17.8118.70 (1.22)71.6661.66 Ipé (0.79)75.3642.59 (0.55)5.618.87 (1.01)16.8916.46 (2.59)17.8118.70 (1.22)71.6661.66 OkouméIpé 42.59(0.79)75.3642.59 8.87(0.55)5.618.87 16.46(1.01)16.8916.46 18.70(2.59)17.8118.70 61.66(1.22)71.6661.66 OkouméIpé Ip é (0.79)(1.13)75.36 (0.55)(0.61)5.61 (1.01)(0.57)16.89 (2.59)(0.65)17.81 (1.22)(1.69)71.66 Okoumé (0.79)(0.79)(1.13)75.36 (0.55)(0.55)(0.61)5.61 (1.01)(1.01)(0.57)16.89 (2.59)(2.59)(0.65)17.81 (1.22)(1.22)(1.69)71.66 Okoumé (1.13)75.36 (0.61)5.61 (0.57)16.89 (0.65)17.81 (1.69)71.66 Okoumé (1.13)(1.13)75.36 (0.61)(0.61)5.61 (0.57)(0.57)16.89 (0.65)(0.65)17.81 (1.69)(1.69)71.66 Okoumé (1.13)47.6975.36 (0.61)14.565.61 (0.57)16.2316.89 (0.65)21.8317.81 (1.69)48.2671.66 Okoumé 75.36(1.13)47.6975.36 5.61(0.61)14.565.61 16.89(0.57)16.2316.89 17.81(0.65)21.8317.81 71.66(1.69)48.2671.66 OkouméTineoOkoum é (1.13)47.6975.36 (0.61)14.565.61 (0.57)16.2316.89 (0.65)21.8317.81 (1.69)48.2671.66 OkouméTineo (1.13)(1.13)(4.98)47.69 (0.61)(0.61)(1.81)14.56 (0.57)(0.57)(0.99)16.23 (0.65)(0.65)(1.77)21.83 (1.69)(1.69)(2.83)48.26 Tineo (1.13)(4.98)47.69 (0.61)(1.81)14.56 (0.57)(0.99)16.23 (0.65)(1.77)21.83 (1.69)(2.83)48.26 Tineo (4.98)47.69 (1.81)14.56 (0.99)16.23 (1.77)21.83 (2.83)48.26 Tineo (4.98)(4.98)47.69 (1.81)(1.81)14.56 (0.99)(0.99)16.23 (1.77)(1.77)21.83 (2.83)(2.83)48.26 Tineo 47.69(4.98)62.0347.69 14.56(1.81)11.7614.56 16.23(0.99)16.3516.23 21.83(1.77)20.1521.83 48.26(2.83)54.3048.26 TineoTineo (4.98)62.0347.69 (1.81)11.7614.56 (0.99)16.3516.23 (1.77)20.1521.83 (2.83)54.3048.26 DarkredTineo meranti (4.98)(4.98)62.0347.69 (1.81)(1.81)11.7614.56 (0.99)(0.99)16.3516.23 (1.77)(1.77)20.1521.83 (2.83)(2.83)54.3048.26 DarkredTineo meranti (4.98)(1.52)62.03 (1.81)(0.81)11.76 (0.99)(0.64)16.35 (1.77)(0.87)20.15 (2.83)(1.56)54.30 Darkred meranti (4.98)(1.52)62.03 (1.81)(0.81)11.76 (0.99)(0.64)16.35 (1.77)(0.87)20.15 (2.83)(1.56)54.30 Darkred meranti (1.52)62.03 (0.81)11.76 (0.64)16.35 (0.87)20.15 (1.56)54.30 DarkredDarkred meranti 62.03(1.52)(1.52)62.03 11.76(0.81)(0.81)11.76 16.35(0.64)(0.64)16.35 20.15(0.87)(0.87)20.15 54.30(1.56)(1.56)54.30 Darkred meranti (1.52)54.5962.03 (0.81)13.2211.76 (0.64)21.9216.35 (0.87)25.6020.15 (1.56)58.9354.30 Darkredmeranti meranti (1.52)(1.52)54.5962.03 (0.81)(0.81)13.2211.76 (0.64)(0.64)21.9216.35 (0.87)(0.87)25.6020.15 (1.56)(1.56)58.9354.30 DarkredYellow merantibalau (1.52)54.5962.03 (0.81)13.2211.76 (0.64)21.9216.35 (0.87)25.6020.15 (1.56)58.9354.30 DarkredYellow merantibalau (1.52)(0.92)54.59 (0.81)(0.83)13.22 (0.64)(0.88)21.92 (0.87)(1.12)25.60 (1.56)(1.02)58.93 Yellow balau (1.52)(0.92)54.59 (0.81)(0.83)13.22 (0.64)(0.88)21.92 (0.87)(1.12)25.60 (1.56)(1.02)58.93 Yellow balau 54.59(0.92)54.59 13.22(0.83)13.22 21.92(0.88)21.92 25.60(1.12)25.60 58.93(1.02)58.93 YellowYellow balau balau (0.92)(0.92)54.59 (0.83)(0.83)13.22 (0.88)(0.88)21.92 (1.12)(1.12)25.60 (1.02)(1.02)58.93 Yellow balau (0.92)(0.92)59.4054.59 (0.83)(0.83)13.8613.22 (0.88)(0.88)21.2921.92 (1.12)(1.12)25.4125.60 (1.02)(1.02)56.9358.93 Yellow balau (0.92)59.4054.59 (0.83)13.8613.22 (0.88)21.2921.92 (1.12)25.4125.60 (1.02)56.9358.93 MacassarYellow balau ebony (0.92)59.4054.59 (0.83)13.8613.22 (0.88)21.2921.92 (1.12)25.4125.60 (1.02)56.9358.93 MacassarYellow balau ebony (0.92)(0.80)59.40 (0.83)(0.68)13.86 (0.88)(0.81)21.29 (1.12)(0.91)25.41 (1.02)(1.23)56.93 MacassarMacassar ebony 59.40(0.92)(0.80)59.40 13.86(0.83)(0.68)13.86 21.29(0.88)(0.81)21.29 25.41(1.12)(0.91)25.41 56.93(1.02)(1.23)56.93 Macassar ebony (0.80)59.40 (0.68)13.86 (0.81)21.29 (0.91)25.41 (1.23)56.93 Macassarebony ebony (0.80)(0.80)(0.80)59.40 (0.68)(0.68)(0.68)13.86 (0.81)(0.81)(0.81)21.29 (0.91)(0.91)(0.91)25.41 (1.23)(1.23)(1.23)56.93 Macassar ebony (0.80)60.5759.40 (0.68)10.2813.86 (0.81)25.4221.29 (0.91)27.5025.41 (1.23)67.9356.93 Macassar ebony (0.80)60.5759.40 (0.68)10.2813.86 (0.81)25.4221.29 (0.91)27.5025.41 (1.23)67.9356.93 MacassarDoussié ebony (0.80)60.5759.40 (0.68)10.2813.86 (0.81)25.4221.29 (0.91)27.5025.41 (1.23)67.9356.93 MacassarDoussié ebony 60.57(0.80)(6.61)60.57 10.28(0.68)(1.89)10.28 25.42(0.81)(2.09)25.42 27.50(0.91)(1.81)27.50 67.93(1.23)(4.80)67.93 Doussié (0.80)(6.61)60.57 (0.68)(1.89)10.28 (0.81)(2.09)25.42 (0.91)(1.81)27.50 (1.23)(4.80)67.93 DoussiéDoussi é (6.61)(6.61)60.57 (1.89)(1.89)10.28 (2.09)(2.09)25.42 (1.81)(1.81)27.50 (4.80)(4.80)67.93 Doussié (6.61)(6.61)60.57 (1.89)(1.89)10.28 (2.09)(2.09)25.42 (1.81)(1.81)27.50 (4.80)(4.80)67.93 Doussié (6.61)49.9360.57 (1.89)10.8510.28 (2.09)18.1925.42 (1.81)21.2227.50 (4.80)59.2467.93 Doussié (6.61)49.9360.57 (1.89)10.8510.28 (2.09)18.1925.42 (1.81)21.2227.50 (4.80)59.2467.93 CerejeiraDoussié 49.93(6.61)49.9360.57 10.85(1.89)10.8510.28 18.19(2.09)18.1925.42 21.22(1.81)21.2227.50 59.24(4.80)59.2467.93 CerejeiraDoussié (6.61)(3.34)49.93 (1.89)(1.52)10.85 (2.09)(1.34)18.19 (1.81)(1.59)21.22 (4.80)(3.46)59.24 CerejeiraCerejeira (3.34)(6.61)(3.34)49.93 (1.52)(1.89)(1.52)10.85 (1.34)(2.09)(1.34)18.19 (1.59)(1.81)(1.59)21.22 (3.46)(4.80)(3.46)59.24 Cerejeira (3.34)49.93 (1.52)10.85 (1.34)18.19 (1.59)21.22 (3.46)59.24 Cerejeira (3.34)(3.34)49.93 (1.52)(1.52)10.85 (1.34)(1.34)18.19 (1.59)(1.59)21.22 (3.46)(3.46)59.24 Cerejeira (3.34)46.8149.93 (1.52)17.5010.85 (1.34)16.9818.19 (1.59)24.4021.22 (3.46)44.1159.24 Cerejeira 46.81(3.34)46.8149.93 17.50(1.52)17.5010.85 16.98(1.34)16.9818.19 24.40(1.59)24.4021.22 44.11(3.46)44.1159.24 CerejeiraBubinga (3.34)46.8149.93 (1.52)17.5010.85 (1.34)16.9818.19 (1.59)24.4021.22 (3.46)44.1159.24 CerejeiraBubingaBubinga (1.23)(3.34)(1.23)46.81 (0.89)(1.52)(0.89)17.50 (1.17)(1.34)(1.17)16.98 (1.20)(1.59)(1.20)24.40 (2.00)(3.46)(2.00)44.11 Bubinga (3.34)(1.23)46.81 (1.52)(0.89)17.50 (1.34)(1.17)16.98 (1.59)(1.20)24.40 (3.46)(2.00)44.11 ForestsBubinga 2019 , 10 , x FOR PEER REVIEW (1.23)46.81 (0.89)17.50 (1.17)16.98 (1.20)24.40 (2.00)44.11 6 of 14 Forests 2019 , 10, x FOR PEER REVIEW (1.23)46.81 (0.89)17.50 (1.17)16.98 (1.20)24.40 (2.00)44.11 6 of 14 ForestsBubinga 2019 , 10 , x FOR PEER REVIEW (1.23)46.81 (0.89)17.50 (1.17)16.98 (1.20)24.40 (2.00)44.11 6 of 14 ForestsBubinga 2019 , 10 , x FOR PEER REVIEW 53.56(1.23)46.8153.56 8.08(0.89)17.508.08 19.63(1.17)16.9819.63 21.27(1.20)24.4021.27 67.36(2.00)44.1167.36 6 of 14 OvengolBubingaOvengol (1.23)53.56 (0.89)8.08 (1.17)19.63 (1.20)21.27 (2.00)67.36 OvengolBubinga (4.65)(4.65)(1.23)53.5646.81 (1.07)(1.07)(0.89)17.508.08 (4.38)(4.38)(1.17)19.6316.98 (4.33)(4.33)(1.20)21.2724.40 (2.69)(2.69)(2.00)67.3644.11 OvengolBubinga 46.92(4.65)(1.23)53.56 15.43(1.07)(0.89)8.08 18.97(4.38)(1.17)19.63 24.46(4.33)(1.20)21.27 50.83(2.69)(2.00)67.36 MerbauOvengol (4.65)(1.23)46.9253.56 (1.07)(0.89)15.438.08 (4.38)(1.17)18.9719.63 (4.33)(1.20)24.4621.27 (2.69)(2.00)50.8367.36 OvengolMerbau (1.57)46.9253.56(4.65) (0.53)15.43(1.07)8.08 (1.12)18.9719.63(4.38) (1.09)24.4621.27(4.33) (1.37)50.8367.36(2.69) OvengolMerbau 46.92(1.57)(4.65)46.9253.56 15.43(0.53)(1.07)15.438.08 18.97(1.12)(4.38)18.9719.63 24.46(1.09)(4.33)24.4621.27 50.83(1.37)(2.69)50.8367.36 OvengolMerbauMerbau (1.57)(4.65)53.56 (0.53)(1.07)8.08 (1.12)(4.38)19.63 (1.09)(4.33)21.27 (1.37)(2.69)67.36 Ovengol (1.57)(1.57)(4.65)53.56 (0.53)(0.53)(1.07)8.08 (1.12)(1.12)(4.38)19.63 (1.09)(1.09)(4.33)21.27 (1.37)(1.37)(2.69)67.36 Ovengol (4.65)53.56 (1.07)8.08 (4.38)19.63 (4.33)21.27 (2.69)67.36 Ovengol 50.79(4.65) 14.68(1.07) 22.49(4.38) 26.88(4.33) 56.63(2.69) Santos rosewood (4.65)50.79 (1.07)14.68 (4.38)22.49 (4.33)26.88 (2.69)56.63 50.7950.79 14.6814.68 22.4922.49 26.8826.88 56.6356.63 Santos rosewoodSantos (3.39)50.79 (1.31)14.68 (3.13)22.49 (3.23)26.88 (2.44)56.63 Santos rosewood (3.39)(3.39) (1.31)(1.31) (3.13)(3.13) (3.23)(3.23) (2.44)(2.44) Santosrosewood rosewood (3.39) (1.31) (3.13) (3.23) (2.44) (3.39) (1.31) (3.13) (3.23) (2.44) 55.85 10.09 19.18 21.68 62.24 Zebrano 55.8555.85 10.0910.09 19.1819.18 21.6821.68 62.2462.24 ZebranoZebrano (4.91)(4.91)55.85 (1.06)(1.06)10.09 (1.49)(1.49)19.18 (1.63)(1.63)21.68 (2.18)(2.18)62.24 Zebrano (4.91)55.85 (1.06)10.09 (1.49)19.18 (1.63)21.68 (2.18)62.24 Zebrano (4.91) (1.06) (1.49) (1.63) (2.18) (4.91) (1.06) (1.49) (1.63) (2.18) 34.8834.88 7.897.89 10.3310.33 13.0213.02 52.4252.42 WengéWeng é (1.68)34.88 (0.64)7.89 (1.30)10.33 (1.24)13.02 (3.38)52.42 Wengé (1.68)34.88 (0.64)7.89 (1.30)10.33 (1.24)13.02 (3.38)52.42 Wengé (1.68)34.88 (0.64)7.89 (1.30)10.33 (1.24)13.02 (3.38)52.42 Wengé (1.68) (0.64) (1.30) (1.24) (3.38) (1.68) (0.64) (1.30) (1.24) (3.38) 43.78 31.42 26.72 41.26 40.34 Padouk 43.78 31.42 26.72 41.26 40.34 Padouk (2.05)43.78 (1.61)31.42 (2.02)26.72 (2.32)41.26 (1.57)40.34 Padouk (2.05)43.78 (1.61)31.42 (2.02)26.72 (2.32)41.26 (1.57)40.34 Padouk (2.05) (1.61) (2.02) (2.32) (1.57) (2.05) (1.61) (2.02) (2.32) (1.57) 53.04 13.88 18.34 23.01 52.90 Sapelli 53.04 13.88 18.34 23.01 52.90 Sapelli (1.69)53.04 (0.88)13.88 (0.72)18.34 (0.94)23.01 (1.62)52.90 Sapelli (1.69)53.04 (0.88)13.88 (0.72)18.34 (0.94)23.01 (1.62)52.90 Sapelli (1.69) (0.88) (0.72) (0.94) (1.62) (1.69) (0.88) (0.72) (0.94) (1.62) 63.52 8.49 26.20 27.57 71.70 Iroko 63.52 8.49 26.20 27.57 71.70 Iroko (6.78)63.52 (0.88)8.49 (5.69)26.20 (5.59)27.57 (2.54)71.70 Iroko (6.78)63.52 (0.88)8.49 (5.69)26.20 (5.59)27.57 (2.54)71.70 Iroko (6.78) (0.88) (5.69) (5.59) (2.54) (6.78) (0.88) (5.69) (5.59) (2.54) 50.72 17.36 23.84 29.50 53.92 Karri 50.72 17.36 23.84 29.50 53.92 Karri (2.07)50.72 (1.13)17.36 (1.59)23.84 (1.83)29.50 (1.32)53.92 Karri (2.07)50.72 (1.13)17.36 (1.59)23.84 (1.83)29.50 (1.32)53.92 Karri (2.07) (1.13) (1.59) (1.83) (1.32) (2.07) (1.13) (1.59) (1.83) (1.32) 59.25 8.05 17.24 19.03 64.95 Blue gum 59.25 8.05 17.24 19.03 64.95 Blue gum (3.37)59.25 (0.74)8.05 (1.23)17.24 (1.27)19.03 (1.98)64.95 Blue gum (3.37)59.25 (0.74)8.05 (1.23)17.24 (1.27)19.03 (1.98)64.95 Blue gum (3.37) (0.74) (1.23) (1.27) (1.98) (3.37) (0.74) (1.23) (1.27) (1.98) 45.06 17.61 14.34 22.75 39.45 Maçaranduba 45.06 17.61 14.34 22.75 39.45 Maçaranduba (2.16)45.06 (2.39)17.61 (0.99)14.34 (2.23)22.75 (3.79)39.45 Maçaranduba (2.16)45.06 (2.39)17.61 (0.99)14.34 (2.23)22.75 (3.79)39.45 Maçaranduba (2.16) (2.39) (0.99) (2.23) (3.79) (2.16) (2.39) (0.99) (2.23) (3.79) 49.85 12.08 18.95 22.49 57.47 Makoré 49.85 12.08 18.95 22.49 57.47 Makoré (2.24)49.85 (0.88)12.08 (1.10)18.95 (1.15)22.49 (2.10)57.47 Makoré (2.24)49.85 (0.88)12.08 (1.10)18.95 (1.15)22.49 (2.10)57.47 Makoré (2.24) (0.88) (1.10) (1.15) (2.10) Notes: Mean values are from 16 measurements.(2.24) Standard(0.88) deviations(1.10) are in italic(1.15) and parentheses. (2.10) Notes: Mean values are from 16 measurements. Standard deviations are in italic and parentheses. Notes: Mean values are from 16 measurements. Standard deviations are in italic and parentheses. Notes: Mean values are from 16 measurements. Standard deviations are in italic and parentheses. * The studied tropical woods differed mainly in the lightness L *, which ranged between 34.88 The studied tropical woods differed mainly in the lightness L*, which ranged between 34.88 (“veryThe dark” studied wengé), tropical 43.78 woods (“dark” differed padouk), mainly 63.58 in (“light” the lightness iroko) andL*, which75.36 (“very ranged light” between okoumé). 34.88 (“veryThe dark” studied wengé), tropical 43.78 woods (“dark” differed padouk), mainly 63.58 in (“light” the lightness iroko) andL , which75.36 (“very ranged light” between okoumé). 34.88 Achieved(“very dark” results wengé), are in43.78 an (“dark” accordance padouk), with 63.58 similar (“light” works iroko) disserting and 75.36 specific (“very colour light” and okoumé). texture Achieved(“very dark” results wengé), are 43.78 in an (“dark” accordance padouk), with 63.58 similar (“light” works iroko) disserting and 75.36 specific (“very colour light” and okoumé). texture characteristicsAchieved results of selected are in antropical accordance woods with[7,40 , similar43]. works disserting specific colour and texture characteristicsAchieved results of selected are in antropical accordance woods with[7,40 , similar43]. works disserting specific colour and texture characteristics of selected tropical woods [7,40,43]. * * characteristicsAll 21 tropical of selected woods tropical had the woods colour [ 7parameters,40,43]. a * and b * in a positive sphere of distribution. All 21 tropical woods had the colour parameters a* and b* in a positive sphere of distribution. All 21 tropical woods* had the colour parameters a* and b* in a positive sphere of distribution.* The rednessAll 21 tropical index (+ woodsa *) ranged had from the colour5.61 (okoumé) parameters to 31.42 a and (padouk), b in a positive and the sphereyellowness of distribution. index (+b *) The redness index (+a*) ranged from 5.61 (okoumé) to 31.42 (padouk), and the yellowness index (+b*) fromThe redness 10.33 (wengé) index (+ toa*) 26.72ranged (padouk). from 5.61 This (okoumé) result suggeststo 31.42 (padouk), that woods and coloured the yellowness a brighter index red (+ orb*) fromThe redness 10.33 (wengé) index (+ toa ) 26.72ranged (padouk). from 5.61 This (okoumé) result tosuggests 31.42 (padouk), that woods and coloured the yellowness a brighter index red (+ bor) from 10.33 (wengé) to 26.72 (padouk). This result suggests that woods coloured* a brighter* red or yellow,from 10.33 such (wengé) as padouk, to 26.72 may (padouk).belong also This to darker result species.suggests When that woodsthe values coloured of a * and a brighter b * were redfor 21or yellow, such as padouk, may belong also to darker species. When the values of a* and b* were for 21 tropicalyellow, suchwood as species padouk, evaluated may belong in comparison also to darker to species.their lightness When theL*, differentvalues of tendenciesa* and b* were of linearfor 21 tropicalyellow, suchwood as species padouk, evaluated may belong in comparison also to darker to species.their lightness When theL*, valuesdifferent of tendenciesa and b were of linearfor 21 tropical wood species evaluated* in comparison to their lightness L*, different* tendencies2 of linear correlationtropical wood were species found. evaluated Value a * had in acomparison negative correlation to their lightness against the L*, Ldifferent* (Figure tendencies2A; R 2 = 0.18), of whilelinear correlation were found. Value a* had a negative correlation against the L* (Figure 2A; R2 = 0.18), while thecorrelation b* had a were positive found. correlation Value a* hadagainst a negative the L* (Figure correlation 2B; Ragainst2 = 0.10). the Nishino L* (Figure et 2A;al. [ R432 ]= determined0.18), while thecorrelation b* had a were positive found. correlation Value a hadagainst a negative the L* (Figurecorrelation 2B; Ragainst2 = 0.10). the Nishino L (Figure et 2A;al. [R43 ]= determined0.18), while the b* had a positive correlation* against* the* L* (Figure 2B; R2 = 0.10). Nishino et al. [43] determined similarthe b* had dependences a positive betweencorrelation a * or against b * and theL * for L* 97(Figure wood 2B; species R2 = 0.10).from FrenchNishino Guiana. et al. [ 43] determined similar dependences between a* or b* and L* for 97 wood species from French Guiana. similarThe dependences colour saturation between C*ab a indicates* or b* and the L* for distance 97 wood from species the chromatic from French point Guiana. (a* = 0, b* = 0) on the similarThe dependences colour saturation between C*ab a indicates or b and theL for distance 97 wood from species the chromatic from French point Guiana. (a* = 0, b* = 0) on the The colour* * * saturation C*ab indicates the distance from the chromatic point (a* = 0, b* = 0) on the CIE 1976The Lcolour*a *b * colour saturation space. C *abFor indicates tropical the woods distance the valuesfrom the of colourchromatic saturation point ( aranged* = 0, b* from= 0) on 13.02 the CIE 1976 L*a*b* colour space. For tropical woods the values of colour saturation ranged from 13.02 (wengé—characterizedCIE 1976 L*a*b* colour space. by a little For intensivetropical woods red-yellow the values shade) of to colour 41.26 saturation(padouk—characterized ranged from 13.02by a (wengé—characterizedCIE 1976 L a b colour space. by a little For tropicalintensive woods red-yellow the values shade) of to colour 41.26 saturation(padouk—characterized ranged from 13.02 by a strong(wengé—characterized intensive red-yellow by a shade). little intensive Graphical red-yellow analysis ofshade) the C *toab against41.26 (padouk—characterized the L* for 21 tropical woods by a (wengé—characterized by a little intensive red-yellow shade) to*ab 41.26 (padouk—characterized* by a strong intensive red-yellow shade). Graphical analysis of the C* against the L* for 21 tropical woods isstrong present intensive in Figure red-yellow 2C. The shade). C*ab exhibited Graphical only analysis a minimal of the decrease C*ab against at higher the L * valuesfor 21 tropicalof lightness woods L* strong intensive red-yellow shade).*ab Graphical analysis of the C ab against the L for 21 tropical woods* is present in Figure 2C. The C* exhibited only a minimal decrease at higher values of lightness L* is present in Figure 2C. The C*ab exhibited2 only a minimal decrease at higher values of lightness L* withis present zero coefficient in Figure 2C.of determination The C ab exhibited (R 2 = only0.00), a i.e. minimal was not decrease found significant at higher correlation.values of lightness L with zero coefficient of determination (R2 = 0.00), i.e. was not found significant correlation. withThe zero huecoefficient tone angle of determination hab ranges for (R 2 wood = 0.00), between i.e. was 0°not and found 90° significant (the first correlation. quadrate), where 0° with zero coefficient of determinationab (R = 0.00), i.e. was not found significant correlation. The hue tone angle h ranges for wood between 0° and 90° (the first quadrate), where 0° representsThe hue the red tone colour angle and hab ranges90° represents for wood the yellow between colour. 0° and The 90° yellow (the shade first quadrate), prevailed to where the red 0° representsThe hue the red tone colour angle and hab ranges90° represents for wood the betweenyellow colour. 0° and The 90° yellow (the shade first quadrate), prevailed to where the red 0° represents the red colour and 90° represents the yellow colour. The yellow shade prevailed to the red

Forests 2019, 10, x FOR PEER REVIEW 6 of 14 Forests 2019, 10, x FOR PEER REVIEW 6 of 14 Forests 2019, 10, x FOR PEER REVIEW 6 of 14 Forests 2019, 10, x FOR PEER REVIEW 6 of 14 Forests 2019, 10, x FOR PEER REVIEW 6 of 14 Forests 2019, 10, x FOR PEER REVIEW 46.92 15.43 18.97 24.46 50.83 6 of 14 ForestsMerbau 2019, 10 , x FOR PEER REVIEW 46.92 15.43 18.97 24.46 50.83 6 of 14 Merbau (1.57)46.92 (0.53)15.43 (1.12)18.97 (1.09)24.46 (1.37)50.83 Merbau (1.57)46.92 (0.53)15.43 (1.12)18.97 (1.09)24.46 (1.37)50.83 Merbau (1.57)46.92 (0.53)15.43 (1.12)18.97 (1.09)24.46 (1.37)50.83 Merbau 46.92(1.57) 15.43(0.53) 18.97(1.12) 24.46(1.09) 50.83(1.37) Merbau (1.57)46.92 (0.53)15.43 (1.12)18.97 (1.09)24.46 (1.37)50.83 Merbau (1.57)50.79 (0.53)14.68 (1.12)22.49 (1.09)26.88 (1.37)56.63 Santos rosewood (1.57)50.79 (0.53)14.68 (1.12)22.49 (1.09)26.88 (1.37)56.63 Santos rosewood (3.39)50.79 (1.31)14.68 (3.13)22.49 (3.23)26.88 (2.44)56.63 Santos rosewood (3.39)50.79 (1.31)14.68 (3.13)22.49 (3.23)26.88 (2.44)56.63 Santos rosewood (3.39)50.79 (1.31)14.68 (3.13)22.49 (3.23)26.88 (2.44)56.63 Santos rosewood 50.79(3.39) 14.68(1.31) 22.49(3.13) 26.88(3.23) 56.63(2.44) Santos rosewood (3.39)55.8550.79 (1.31)10.0914.68 (3.13)19.1822.49 (3.23)21.6826.88 (2.44)62.2456.63 SantosZebrano rosewood (3.39)55.85 (1.31)10.09 (3.13)19.18 (3.23)21.68 (2.44)62.24 ForestsZebrano2019, 10 , 322 (4.91)(3.39)55.85 (1.06)(1.31)10.09 (1.49)(3.13)19.18 (1.63)(3.23)21.68 (2.18)(2.44)62.246 of 14 Zebrano (4.91)55.85 (1.06)10.09 (1.49)19.18 (1.63)21.68 (2.18)62.24 Zebrano (4.91)55.85 (1.06)10.09 (1.49)19.18 (1.63)21.68 (2.18)62.24 Zebrano 55.85(4.91) 10.09(1.06) 19.18(1.49) 21.68(1.63) 62.24(2.18) Zebrano (4.91)55.85 (1.06)10.09 (1.49)19.18 (1.63)21.68 (2.18)62.24 Zebrano 34.88 7.89 10.33 13.02 52.42 Wengé (4.91)34.88 Table 2.(1.06)7.89Cont. (1.49)10.33 (1.63)13.02 (2.18)52.42 Wengé (1.68)(4.91)34.88 (0.64)(1.06)7.89 (1.30)(1.49)10.33 (1.24)(1.63)13.02 (3.38)(2.18)52.42 Wengé (1.68)34.88 (0.64)7.89 (1.30)10.33 (1.24)13.02 (3.38)52.42 Wengé (1.68)34.88 (0.64)7.89 (1.30)10.33 (1.24)13.02 (3.38)52.42 Wengé 34.88(1.68) (0.64)7.89 10.33(1.30) Colour13.02(1.24) Hue Tone52.42(3.38) WengéWood Lightness(1.68)34.88 Redness(0.64)7.89 Yellowness(1.30)10.33 (1.24)13.02 (3.38)52.42 Wengé Visual (1.68)43.78 (0.64)31.42 (1.30)26.72 Saturation(1.24)41.26 Angle(3.38)40.34 PadoukSpecies 43.78L* +31.42a* +26.72b* 41.26 40.34 Padouk (2.05)(1.68)43.78 (1.61)(0.64)31.42 (2.02)(1.30)26.72 *(2.32)(1.24)41.26 (1.57)(3.38)40.34 Padouk (2.05)43.78 (1.61)31.42 (2.02)26.72 C(2.32)41.26ab hab(1.57)40.34 Padouk (2.05)43.78 (1.61)31.42 (2.02)26.72 (2.32)41.26 (1.57)40.34 43.78 31.42 26.72 41.26 40.34 Padouk 43.78(2.05) 31.42(1.61) 26.72(2.02) 41.26(2.32) 40.34(1.57) Padouk (2.05)53.0443.78 (1.61)13.8831.42 (2.02)18.3426.72 (2.32)23.0141.26 (1.57)52.9040.34 PadoukSapelliPadouk (2.05)(2.05)53.04 (1.61)(1.61)13.88 (2.02)(2.02)18.34 (2.32)(2.32)23.01 (1.57)(1.57)52.90 Sapelli (1.69)(2.05)53.04 (0.88)(1.61)13.88 (0.72)(2.02)18.34 (0.94)(2.32)23.01 (1.62)(1.57)52.90 Sapelli (1.69)53.04 (0.88)13.88 (0.72)18.34 (0.94)23.01 (1.62)52.90 Sapelli (1.69)53.04 (0.88)13.88 (0.72)18.34 (0.94)23.01 (1.62)52.90 Sapelli 53.0453.04(1.69) 13.8813.88(0.88) 18.3418.34(0.72) 23.0123.01(0.94) 52.9052.90(1.62) SapelliSapelli (1.69)53.04 (0.88)13.88 (0.72)18.34 (0.94)23.01 (1.62)52.90 Sapelli (1.69)(1.69)63.52 (0.88)(0.88)8.49 (0.72)(0.72)26.20 (0.94)(0.94)27.57 (1.62)(1.62)71.70 Iroko (1.69)63.52 (0.88)8.49 (0.72)26.20 (0.94)27.57 (1.62)71.70 Iroko (6.78)63.52 (0.88)8.49 (5.69)26.20 (5.59)27.57 (2.54)71.70 Iroko 63.52(6.78)63.52 8.49(0.88)8.49 26.20(5.69)26.20 27.57(5.59)27.57 71.70(2.54)71.70 Iroko (6.78)63.52 (0.88)8.49 (5.69)26.20 (5.59)27.57 (2.54)71.70 IrokoIroko (6.78)63.52(6.78) (0.88)(0.88)8.49 (5.69)26.20(5.69) (5.59)27.57(5.59) (2.54)71.70(2.54) Iroko (6.78)50.7263.52 (0.88)17.368.49 (5.69)23.8426.20 (5.59)29.5027.57 (2.54)53.9271.70 IrokoKarri (6.78)50.72 (0.88)17.36 (5.69)23.84 (5.59)29.50 (2.54)53.92 (6.78)50.72 (0.88)17.36 (5.69)23.84 (5.59)29.50 (2.54)53.92 Karri 50.72(2.07) 17.36(1.13) 23.84(1.59) 29.50(1.83) 53.92(1.32) Karri (2.07)50.72 (1.13)17.36 (1.59)23.84 (1.83)29.50 (1.32)53.92 KarriKarri (2.07)(2.07)50.72 (1.13)(1.13)17.36 (1.59)(1.59)23.84 (1.83)(1.83)29.50 (1.32)(1.32)53.92 Karri 50.72(2.07) 17.36(1.13) 23.84(1.59) 29.50(1.83) 53.92(1.32) Karri (2.07)59.2550.72 (1.13)17.368.05 (1.59)17.2423.84 (1.83)19.0329.50 (1.32)64.9553.92 Karri (2.07)59.25 (1.13)8.05 (1.59)17.24 (1.83)19.03 (1.32)64.95 Blue gum 59.25(2.07) 8.05(1.13) 17.24(1.59) 19.03(1.83) 64.95(1.32) Blue gum (3.37)59.25 (0.74)8.05 (1.23)17.24 (1.27)19.03 (1.98)64.95 BlueBlue gum gum (3.37)(3.37)59.25 (0.74)(0.74)8.05 (1.23)(1.23)17.24 (1.27)(1.27)19.03 (1.98)(1.98)64.95 Blue gum (3.37)59.25 (0.74)8.05 (1.23)17.24 (1.27)19.03 (1.98)64.95 Blue gum 59.25(3.37) (0.74)8.05 17.24(1.23) 19.03(1.27) 64.95(1.98) Blue gum (3.37)45.0659.25 (0.74)17.618.05 (1.23)14.3417.24 (1.27)22.7519.03 (1.98)39.4564.95 MaçarandubaBlue gum 45.06(3.37)45.06 17.61(0.74)17.61 14.34(1.23)14.34 22.75(1.27)22.75 39.45(1.98)39.45 (3.37)45.06 (0.74)17.61 (1.23)14.34 (1.27)22.75 (1.98)39.45 MaçarandubaMaçaranduba (2.16)(2.16) (2.39)(2.39) (0.99)(0.99) (2.23)(2.23) (3.79)(3.79) Maçaranduba (2.16)45.06 (2.39)17.61 (0.99)14.34 (2.23)22.75 (3.79)39.45 Maçaranduba (2.16)45.06 (2.39)17.61 (0.99)14.34 (2.23)22.75 (3.79)39.45 Maçaranduba 45.06(2.16) 17.61(2.39) 14.34(0.99) 22.75(2.23) 39.45(3.79) Maçaranduba 49.85(2.16)49.8545.06 12.08(2.39)12.0817.61 18.95(0.99)18.9514.34 22.49(2.23)22.4922.75 57.47(3.79)57.4739.45 MaçarandubaMakoréMakor é (2.16)49.85 (2.39)12.08 (0.99)18.95 (2.23)22.49 (3.79)57.47 Makoré (2.24)(2.24)(2.16)49.85 (0.88)(0.88)(2.39)12.08 (1.10)(1.10)(0.99)18.95 (1.15)(1.15)(2.23)22.49 (2.10)(2.10)(3.79)57.47 Makoré (2.24)49.85 (0.88)12.08 (1.10)18.95 (1.15)22.49 (2.10)57.47 Makoré (2.24)49.85 (0.88)12.08 (1.10)18.95 (1.15)22.49 (2.10)57.47 Makoré 49.85 12.08 18.95 22.49 57.47 Notes: Notes: Mean Mean values values are are from from 16 16 measurements.(2.24)49.85 measurements. StandardStandard(0.88)12.08 deviations deviations(1.10)18.95 are are in italic in italic and(1.15)22.49 parentheses.and parentheses. (2.10)57.47 MakoréNotes: Mean values are from 16 measurements.(2.24) Standard(0.88) deviations(1.10) are in italic(1.15) and parentheses. (2.10) MakoréNotes: Mean values are from 16 measurements.(2.24) Standard(0.88) deviations(1.10) are in italic(1.15) and parentheses. (2.10) Notes: Mean values are from 16 measurements.(2.24) Standard(0.88) deviations(1.10) are in italic(1.15) and parentheses. (2.10) Notes: Mean values are from 16 measurements. Standard deviations* are* in italic and parentheses. TheTheNotes: studiedstudied Mean tropical tropicalvalues are woods woods from differed 16 differed measurements. mainly mainly in Standard the in lightnessthe lightness deviationsL , which L are*, whichin ranged italic ranged and between parentheses. between 34.88 (“very 34.88 TheNotes: studied Mean tropicalvalues are woods from 16 differed measurements. mainly Standard in the lightness deviations L are*, whichin italic ranged and parentheses. between 34.88 dark”(“veryThe weng dark” studiedé), wengé), 43.78 tropical (“dark” 43.78 woods (“dark” padouk), differed padouk), 63.58 mainly (“light” 63.58 in iroko)(“light” the andlightness iroko) 75.36 and (“veryL*, which75.36 light” (“very ranged okoum light” betweené). Achievedokoumé). 34.88 (“veryThe dark” studied wengé), tropical 43.78 woods (“dark” differed padouk), mainly 63.58 in (“light” the lightness iroko) andL*, which75.36 (“very ranged light” between okoumé). 34.88 (“veryThe dark” studied wengé), tropical 43.78 woods (“dark” differed padouk), mainly 63.58 in (“light” the lightness iroko) andL*, which75.36 (“very ranged light” between okoumé). 34.88 resultsAchieved(“veryThe aredark” studied inresults anwengé), accordance tropical are in43.78 an woods with (“dark” accordance similar differed padouk), works with mainly 63.58 similar disserting in (“light” the works specificlightness iroko) disserting colour andL*, which 75.36 and specific texture (“very ranged colour characteristics light” between and okoumé). texture 34.88 of (“veryAchievedThe dark” studied results wengé), tropical are 43.78 in an woods (“dark” accordance differed padouk), with mainly 63.58 similar in (“light” the works lightness iroko) disserting andL , which75.36 specific (“very ranged colour light” between and okoumé). texture 34.88 selected(“verycharacteristicsAchieved dark” tropical results wengé), of woods selected are 43.78 in [ 7 an,tropical40 (“dark”, accordance43]. woods padouk), with[7,40 63.58, similar43]. (“light” works iroko) disserting and 75.36 specific (“very colour light” and okoumé). texture (“verycharacteristicsAchieved dark” results wengé), of selected are 43.78 in antropical (“dark” accordance woods padouk), with[7,40 63.58, similar43]. (“light” works iroko) disserting and 75.36 specific (“very colour light” and okoumé). texture characteristicsAchieved results of selected are in antropical accordance woods with[7,40 , similar43]. * works* * disserting* specific colour and texture AchievedcharacteristicsAllAll 2121 results tropicaltropical of selected are woods woods in an hadtropical had accordance the the colourwoods colour withparameters [7 parameters,40 similar,43]. a worksanda* andb in dissertingb* ain positive a positive specific sphere sphere colourof distribution. of distribution. and texture The AchievedAll 21 results tropical are woods in an had accordance the colour with parameters similar worksa* and dissertingb* in a positive specific sphere colour of distribution. and texture characteristicsAll 21 tropical of *selected woods* tropical had the woods colour [7 parameters,40,43]. a and b in a positive sphere of distribution.* * rednesscharacteristicsThe rednessAll index 21 tropical index (+ ofa selected) (+ ranged woodsa*) ranged tropical from had from 5.61the woods colour (okoum5.61 (okoumé)[7 ,parameters40é), to43 31.42]. to 31.42 (padouk),a* and (padouk), b* in and a thepositive and yellowness the sphereyellowness index of distribution. index (+b ) from (+b*) characteristicsThe redness index of selected (+a*) ranged tropical from woods 5.61 (okoumé)[7,40,43]. to 31.42* (padouk),* and the yellowness index (+b*) The rednessAll 21 tropical index (+ woodsa ) ranged had from the colour 5.61 (okoumé) parameters to 31.42 a* and (padouk), b* in a positive and the sphereyellowness of distribution. index (+b ) 10.33fromThe rednessAll (weng10.33 21 tropical(wengé)é index) to 26.72 (+ woodstoa*) (padouk). 26.72ranged had (padouk). fromthe This colour 5.61 result This (okoumé) parameters suggestsresult tosuggests that31.42a* and woods (padouk), that b* in woods coloureda positive and coloured the a brightersphere yellowness a of brighter red distribution. index or yellow,red (+ bor*) Thefrom rednessAll 10.33 21 tropical(wengé) index (+ woodstoa*) 26.72ranged had (padouk). from the colour 5.61 This (okoumé) parameters result tosuggests 31.42 a and (padouk), that b in woods a positive and coloured the sphere yellowness a of brighter distribution. index red (+ bor*) suchTheyellow,from redness as10.33 padouk,such (wengé) index as padouk, may (+ toa belong*) 26.72ranged may also (padouk).belong from to darker5.61 also This (okoumé) to species. darkerresult to Whensuggestsspecies. 31.42 the (padouk),When that values woods the of andvaluesa* colouredand the ofyellownessb* awere* anda brighter forb* were 21index tropical redfor (+ b21or*) Theyellow,from redness 10.33 such (wengé) index as padouk, (+ ato*) ranged26.72 may (padouk).belong from 5.61 also This (okoumé) to darkerresult tosuggestsspecies. 31.42 (padouk),When that woodsthe andvalues coloured the ofyellowness a* anda brighter b* were index redfor (+ b21or*) yellow,from 10.33 such (wengé) as padouk, to 26.72 may (padouk).belong also This to darkerresult suggestsspecies.* When that woodsthe* values coloured of a* anda brighter b* were redfor 21or woodfromtropicalyellow, 10.33 species suchwood (wengé) as evaluated species padouk, to evaluated26.72 inmay comparison (padouk). belong in comparison also toThis theirto darkerresult lightness to suggestsspecies.theirL lightness, different Whenthat woods theL* tendencies, valuesdifferent coloured of tendencies ofa* and lineara brighter b* were correlation of red linearfor or21 fromtropical 10.33 wood (wengé) species to evaluated26.72 (padouk). in comparison This result to suggeststheir lightness that woods L*, different coloured tendencies* a brighter* of redlinear or tropicalyellow, suchwood as species padouk,* evaluated may belong* in comparison also to darker to species.their lightness When* theL , valuesdifferent* of2 tendenciesa* and2 b* were of linearfor 21* wereyellow,correlationtropical found. suchwood were as Value speciespadouk, found.a had evaluated Value may a negative belong a* had in comparisonaalso correlationnegative to darker correlation to against species.their thelightness against WhenL (Figure the L*, Lvaluesdifferent2* (FigureA; R of = atendencies2A;* 0.18),and R 2 b=*while 0.18),were of theforlinearwhile 21b yellow,correlation such were as padouk, found. Value may belong a* had aalso negative to darker correlation species. against When the* Lvalues* (Figure of a2A; and R2 b= 0.18),were forwhile 21 correlationtropical* wood were species found. evaluated Value a had in comparisona negative* * correlation to their2 lightness against2 theL*, Ldifferent (Figure tendencies2A; R = 0.18), of linearwhile hadtropicalthecorrelation b a* positivehad wood a were positive correlationspecies found. correlation evaluated Value against a* hadagainst thein comparisonaL negative(Figure the L* (Figure 2correlation B;to Rtheir =2B; 0.10). lightness Ragainst2 = Nishino 0.10). theL* , Nishino Ldifferent et* (Figure al. [43 et ]tendencies 2A; determinedal. [ R432 ]= determined0.18), of similar linearwhile tropicalthe b* had wood a positive species correlation evaluated* against in comparison the L* (Figure to their 2B; lightness R2 = 0.10). L , Nishinodifferent* et tendencies al. [432 ] determined of linear thecorrelation b had a were positive found. correlation* Value* a** hadagainst** a negative the* L (Figurecorrelation 2B; Ragainst = 0.10). the Nishino L* (Figure et 2A;al. [R432 ]= determined0.18), while dependencescorrelationsimilarthe b* had dependences awere positive between found. betweencorrelationa Valueor b and a** or hadagainstL b* foraand negative 97the L* wood for L* (Figure97correlation species wood 2B; species from againstR2 = French 0.10).from the French Guiana.NishinoL* (Figure Guiana. et 2A; al. [R43 2 =] 0.18),determined while correlationthesimilar b* had dependences a were positive found. betweencorrelation Value a* orhadagainst b* aand negative the L* for L* (Figure97correlation wood 2B; species againstR2 = 0.10).from the FrenchNishino L (Figure Guiana. et 2A;al. [R43 =] determined0.18), while similar* dependences between**ab a or b and L for* 97 wood species2 from French Guiana.** ** thesimilar bTheThe* had dependences colourcolour a positive saturationsaturation correlationbetween CC*ab a *indicates oragainst b* and the theL* for L distancedistance* (Figure97 wood fromfrom 2B; species R thethe2 = chromaticchromatic0.10). from NishinoFrench pointpoint Guiana. et (a (al.a*= = [ 0,430, b]b *determined = 0) on thethe the bThe had colour a positive saturation correlation C*ab *indicates against* thethe* Ldistance (Figure from 2B; Rthe = chromatic0.10). Nishino point et (al.a* = [ 430, ]b *determined = 0) on the similarThe dependences colour** * ** saturation between C ab a *indicates or b* and theL* for distance 97 wood from species the chromatic from French point Guiana. (a = 0, b = 0) on the CIEsimilarCIE 1976The dependences LcolourL*a*bb* colour coloursaturation between space. space. C * abFora For *indicates or tropicaltropical b* and theL woods woods* for distance 97 the wood values from species the of colourchromaticfrom French saturation point Guiana. ( a ranged* = 0, b* from=from 0) on 13.0213.02 the similarCIE 1976The dependences colourL*a*b* colour saturation between space. C* ab Fora indicates or tropical b and theL woods for distance 97 thewood valuesfrom species the of chromatic colourfrom French saturation point Guiana. ( aranged* = 0, b* =from 0) on 13.02 the (weng(wengé—characterizedCIE 1976Theé—characterized colourL*a*b* coloursaturation space. by a C little* littleabFor indicates tropicalintensive intensive the woods red-yellow red-yellowdistance the valuesfrom shade) shade) the of to chromatic tocolour 41.26 41.26 saturation(padouk—characterized (padouk—characterized point ( aranged* = 0, b* =from 0) on 13.02 by the by a (wengé—characterizedCIE 1976The colourL*a*b* coloursaturation space. by aC little* abFor indicates tropicalintensive the woods red-yellow distance the valuesfrom shade) the of to chromaticcolour 41.26 saturation(padouk—characterized point (a ranged* = 0, b* =from 0) on 13.02 by the a (wengé—characterizedCIE 1976 L*a*b* colour space. by a little For tropicalintensive woods red-yellow the values shade) of to** colour 41.26 saturation(padouk—characterized* ranged from 13.02 by a aCIEstrong strong 1976 intensive intensive L a b colour red-yellow red-yellow space. shade).shade). For tropical Graphical Graphical woods analysis analysis the values of the ofC *abcolour againstagainst saturation the the L* forfor ranged 21 21 tropical from woodswoods 13.02 CIEstrong(wengé—characterized 1976 intensive L*a*b* colour red-yellow space. by a shade). little For tropicalintensive Graphical woods red-yellow analysis the values ofshade) the ofC to abcolour against41.26 saturation(padouk—characterized the L for ranged 21 tropical from woods 13.02 by a strong(wengé—characterized intensive red-yellow by a shade). little** intensive Graphical red-yellow analysis ofshade) the C to*ab against41.26 (padouk—characterized the L* for 21 tropical woods by a** is(wengé—characterizedisstrong presentpresent intensive inin FigureFigure red-yellow2 2C.C. Theby The a shade). ClittleC*abab exhibited intensive Graphical onlyred-yellow analysis a minimal ofshade) the decrease C to*ab 41.26against at (padouk—characterized higherhigher the L * valuesvaluesfor 21 tropical ofof lightnesslightness woods by L La* (wengé—characterizedis present in Figure 2C. by The a littleC*ab exhibited intensive onlyred-yellow a minimal shade) decrease to*ab 41.26 at (padouk—characterizedhigher* values of lightness by La* isstrong present intensive in Figure red-yellow 2C. The shade). C ab exhibited Graphical22 only analysis a minimal of the decrease C* against at higher the L* valuesfor 21 tropicalof lightness woods L withstrongwith zerozero intensive coefficientcoefficient red-yellow ofof determinationdetermination shade).* Graphical ((RR == 0.00), analysis i.e.,i.e. was was of notthe not foundC foundab against significant significant the L correlation.for correlation. 21 tropical woods* withis present zero coefficientin Figure 2C.of determination The C*ab exhibited (R2 = only0.00), a i.e. minimal was not decrease found*ab significant at higher* correlation.values of lightness L* strongis present intensive in Figure red-yellow 2C. The shade). C ab exhibited Graphical2 only analysis a minimal of the◦ decrease C against◦ at higher the L valuesfor 21 tropical of lightness woods L◦ with zero coefficient of determinationab * (R = 0.00), i.e. was not found significant correlation. * iswith presentThe Thezero hue huecoefficientin Figure tone tone angle angle2C. of determination The hhab Cranges*ab exhibited for (R 2 wood = only0.00), betweena i.e.minimal was 0not0° decreaseand found 90 90° significant at(the higher first first valuescorrelation. quadrate), quadrate), of lightness where where 0 0°L* is presentThe huein Figure tone angle2C. The hab Crangesab exhibited for 2 wood only betweena minimal 0° decrease and 90° at (the higher first values quadrate), of lightness where 0°L with Thezero huecoefficient tone angle of determination hab ranges◦ for (R 2 wood = 0.00), between i.e. was not 0° and found 90° significant (the first correlation. quadrate), where 0° representswithrepresents Thezero huecoefficient thethe redred tone colourcolour angle of determination andand hab 90ranges90° represents for (R 2 wood= 0.00), thethe yellowyellow between i.e. was colour.colour. not 0° andfound TheThe 90° yellow yellowsignificant (the shadeshade first correlation. quadrate), prevailed toto where thethe redred 0° withrepresents Thezero huecoefficient the tonered colour angle of determination andhab ranges90° represents for (R wood = 0.00), the betweenyellow i.e. was colour. not 0° andfound The 90° yellowsignificant (the shade first correlation. quadrate), prevailed to where the red 0° shaderepresentsThe for hue a the vast tonered majority colour angle andofhab tested ranges90° represents tropical for wood woods, the betweenyellow typically colour. 0° andfor The iroko 90° yellow (the and okoumshadefirst quadrate), prevailedé. On the whereto contrary, the red 0° representsThe hue the tonered colour angle andhab ranges90° represents for wood the betweenyellow colour. 0° and The 90° yellow (the firstshade quadrate), prevailed whereto the red 0° represents the red colour and 90° represents the yellow colour. The yellow shade prevailed to the red forrepresents padouk, the having red colour the most and red90° andrepresents yellow the striking yellow shades, colour. a The slightly yellow more shade dominant prevailed was to thethe redred represents the red colour and 90° represents the yellow colour. The yellow shade prevailed to the red shade. A reasonable positive linear correlation between the hue tone angle h and the lightness L* of ab 2 individual tropical woods is presented in Figure2D( R = 0.46). Forests 2019, 10, x FOR PEER REVIEW 7 of 14

shade for a vast majority of tested tropical woods, typically for iroko and okoumé. On the contrary, for padouk, having the most red and yellow striking shades, a slightly more dominant was the red * Forestsshade.2019 A ,reasonable10, 322 positive linear correlation between the hue tone angle hab and the lightness7 L of 14of individual tropical woods is presented in Figure 2D (R2 = 0.46).

a* = 26.71 − 0.26·L* b* = 11.70 + 0.14·L* R² = 0.18 p = 0.058 R² = 0.10 p = 0.166

(A) (B)

C*ab = 24.75 − 0.02·L* hab = 19.49 + 0.71·L* R² = 0.00 p = 0.882 R² = 0.46 p = 0.001

(C) (D)

Figure 2. LinearLinear correlations correlations between between the the lightness lightness L* andL* and the colour the colour coordinates coordinates a*, b* (aA,*, bB*),( A,theB colour), the * * coloursaturation saturation C ab (C),C andab ( Cthe), and hue thetone hue angle tone hab angle (D)—forhab (D 21)—for original 21 original tropical tropicalwood species. wood species.

This result suggests suggests that tropical woods with a dominant yellow shade are usually lighter. lighter. * NNémethémeth [[4444]] alsoalso foundfound aa linearlinear correlationcorrelation between between the the lightness lightnessL L*and and thethe huehue angleangleh habab examining thethe colourcolour co-ordinatesco-ordinates ofof differentdifferent temperatetemperate woodwood species.species.

3.2. Colour of Tropical WoodsWoods ExposedExposed toto thethe FungusFungus ConiophoraConiophora puteanaputeana Woods attacked attacked by by the the brown-rot brown-rot fungi fungi gradually gradually acquire acquire deeper deeper shades of brownof yellow of yellow[15,22,27[15,37,22,45,27]., 37 However,,45]. However, specific specific colour colour changes changes during during action action of of the the brown-rot brown-rot fungi fungi can can also occur, dependingdepending onon thethe woodwood speciesspecies [37,,46], thethe historyhistory of woodwood ageing before fungal attack [ 15], thethe degreedegree andand uniformityuniformity ofof decaydecay [[4747],], oror thethe specificspecific enzymes,enzymes, FentonFenton andand otherother low-molecularlow-molecular degradation systems,systems, andand pigmentspigments producedproduced byby fungalfungal myceliamycelia [[4545].]. Weight losseslosses ofof 2121 tropicaltropical woodswoods attackedattacked forfor 66 weeksweeks byby thethe brown-rotbrown-rot fungusfungus C.C. puteanaputeana * rangedranged from 0.08%0.08% toto 6.48%6.48% (Table(Table3 ).3). The The differences differences of of the the lightness lightness ∆∆LL * andand otherother colourimetriccolourimetric parameters ∆a*, ∆b*, ∆C* , ∆h and ∆E* , determined as a difference between the fungal-attacked parameters ∆a*, ∆b*, ∆C*ab, ∆habab and ΔE*abab , determined as a difference between the fungal-attacked and the original tropical wood,wood, are documenteddocumented in Table3 3.. Visualization, Visualization, together together with with the the pantone pantone swatches,swatches, ofof thethe toptop surfacessurfaces of of selected selected tropical tropical woods woods before before and and after after their their exposure exposure to toC. C. puteana puteanais shownis shown in in Figure Figure3. 3.

Forests 2019, 10, 322 8 of 14 Forests 2019, 10, x FOR PEER REVIEW 8 of 14

Original

Fungal attacked

Okoumé Wengé Padouk Sapelli Iroko Figure 3. Visualization and pantone swatches of the top surfaces of selected tropical woods before and Figure 3. Visualization and pantone swatches of the top surfaces of selected tropical woods before after exposure to C. puteana. and after exposure to C. puteana. After exposition to the brown-rot fungus C. puteana, the top surfaces of the darkest tropical woods After exposition to the brown-rot fungus C. puteana, the top surfaces of the darkest tropical wengé and ipé (Table2) developed significantly lighter shades with the lightness increase ∆L* +10.46 woods wengé and ipé (Table 2) developed significantly lighter shades with the lightness increase ΔL* and +2.47 (Table3). This “unexpected” result can be explained by a washout or deterioration of +10.46 and +2.47 (Table 3). This “unexpected” result can be explained by a washout or deterioration dark extractives present in darker wood species during the mycological test performed in humid of dark extractives present in darker wood species during the mycological test performed in humid environment in Petri dishes. On the contrary, the most noticeable darkening was observed in the top environment in Petri dishes. On the contrary, the most noticeable darkening was observed in the top surfaces of the lightest and medium light tropical woods sapelli, okoumé, iroko and ovengol with the surfaces of the lightest and medium light tropical woods sapelli, okoumé, iroko and ovengol with the ∆L* from −21.54 to −11.08 (Table3). This “expected” result can be explained by degradation of white ΔL* from −21.54 to −11.08 (Table 3). This “expected” result can be explained by degradation of white C. puteana cellulosecellulose and and hemicelluloses hemicelluloses in in presence presence of of hydrolases hydrolases and and Fenton Fenton agent agent produced produced by byC. puteana [45[].45 ]. PreviousPrevious studies studies have have also also reported reported a adarkening darkening of of lighter lighter European European woods woods ( (beech and and ) pine) due due to to decaydecay processes processes [ [1515,16,16].]. * AA pronounced pronounced shade shade of of the the red red due due to to C.C. puteana puteana obtainedobtained only only wengé, wengé ,with with ∆a*a +4.98.+4.98. A Alighter lighter * shadeshade of of red red obtained obtained okoumé, okoumé ,zebrano, zebrano, iroko, iroko, and and blue blue gum, gum, with with a∆* afromfrom +0.31 +0.31 to to+2.53 +2.53 (Table (Table 3).3 ). * Conversely,Conversely, the the other other tropical woods woods developed developed a a greener greener shade, shade, with with ∆aa* fromfrom −0.22−0.22 to to −7.76,−7.76, the the * mostmost markedly markedly sapelli, sapelli, padouk padouk and and macaranduba, macaranduba, with with ∆aa* ≥≥ −5.68 −5.68 (Table (Table 3).3 ).The The significant significant greening greening ofof padouk padouk may may be be justified justified by by its its intensive intensive red red shade shade in in the the original original state state (Table (Table 2).2). TheThe majority majority of of tropical tropical woods woods attacked attacked by by C.C. puteana puteana obtainedobtained a more a more yellow yellow shade, shade, typically typically * wengé,wengé, okoumokouméé and and blue blue gum, gum, with with∆b fromb* from +4.42 +4.42 to +10.05. to +10.05. However, However, three three tropical tropical woods—padouk, woods— * padouk,sapelli, andsapelli, yellow and balau—showedyellow balau—showed a significant a significant tendency tendency to become to become bluer, with bluer,∆b withfrom b−* from3.08 to −3.08−8.74 to (Table −8.743 (Table). 3). * AfterAfter fungal fungal attack, attack, a a significant significant positive positive change change in in the the colour colour saturation saturation ∆CC*ab hadab had wengé weng +11.16,é +11.16, okouméokoumé +5.93, and blueblue gumgum +5.15 +5.15 (Table (Table3). 3). It isIt anis interestingan interesting knowledge, knowledge, because because the original the original weng é wengéwas the was darkest the darkest species species and okoum and okouméé the lightest the lightest one (Table one 2(Table). On the2). contrary,On the contrary, an evident an evident negative * * negativechange inchange∆C ab inhad C sapelli,*ab had sapelli, padouk, padouk, and yellow and yellow balau, balau, with with∆C abCfrom*ab from−4.04 −4.04 to to− −10.8410.84 (Table(Table3 ). 3).However However in ain summary, a summary, the the colour colour saturation saturation of the of testedthe tested original original or fungal-attacked or fungal-attacked tropical tropical woods woodshad no had significance no significance to their to lightness their lightness (Figure (Figures2C, Figure 2C,4 4C).C). TheThe positive positive differences differences in in the the hue hue tone tone angle angle ∆habh abindicateindicate that that the the wood wood surfaces surfaces changed changed due due toto the the brown-rot brown-rot fungus fungus more more towards towards yellowish yellowish as as to to reddish. reddish. The The largest largest positive positive change change in in h∆abh ab waswas observed observed for for maçaranduba, maçaranduba, bubinga, bubinga, dark dark red red meranti, meranti, and and sapelli sapelli in in range range from from +13.46 +13.46 to to+7.21 +7.21 (Table(Table 33).). AA significantlysignificantly negative ∆hhabab, connected, connected with with more more evident evident redness redness as asyellowing, yellowing, obtained obtained padoukpadouk −5.49,−5.49, and and iroko iroko −4.30.−4.30. Statistically Statistically insignificant insignificant redness redness occurred occurred for blue for gum, blue ovengol, gum, ovengol, and zebrano,and zebrano, with withhab from∆hab −0.99from to− 0.99−0.09 to (Table−0.09 3). (Table3).

Forests 2019, 10, 322 9 of 14

Table 3. Weight loss and relative change of colourimetric parameters of 21 tropical woods caused by C. puteana.

* * * * * Wood species ∆m ∆L ∆a ∆b ∆C ab ∆hab ∆E ab Ipé 0.20 2.47 a −0.59 c 0.01 d −0.26 d 1.68 b 2.63 (0.03) (1.32) (0.50) (0.31) (0.29) (1.56) (1.26) Okoumé 6.48 −15.74 a 1.20 b 5.80 a 5.93 a 1.70 d 16.84 (2.98) (1.55) (0.23) (0.50) (0.49) (0.51) (1.34) Tineo 5.38 −3.59 d −1.88 b 1.41 c −0.11 d 6.03 a 4.44 (3.71) (1.63) (1.12) (0.43) (0.92) (2.10) (1.68) Dark red 0.22 −8.44 a −2.29 a 3.28 a 1.71 a 9.90 a 9.43 meranti (0.09) (0.96) (0.27) (1.04) (0.94) (1.70) (0.70) Yellow balau 0.40 −8.61 a −2.77 a −3.08 a −4.04 a 2.04 b 9.59 (0.08) (1.06) (1.00) (0.95) (1.17) (1.77) (1.47) Macassar 0.52 −3.48 a −1.88 a −1.76 a −2.49 a 1.57 a 4.73 ebony (0.30) (1.87) (0.31) (0.84) (0.86) (0.49) (0.81) Doussié 1.63 −2.51 d −0.91 d −0.76 d −1.23 d 1.36 d 3.05 (1.51) (1.68) (0.76) (0.66) (0.84) (1.07) (1.60) Cerejeira 0.30 −3.51 b −2.89 b −1.86 b −2.89 b 5.73 c 4.98 (0.15) (2.26) (1.57) (1.28) (1.67) (2.12) (2.93) Bubinga 0.96 −3.81 a −3.87 a 1.89 a −1.11 c 10.29 a 5.96 (0.13) (1.24) (0.85) (0.47) (0.90) (1.10) (0.15) Ovengol 0.61 −11.08 a −0.46 d −1.81 a −1.83 b −0.84 d 11.28 (1.02) (1.28) (0.48) (0.84) (0.87) (1.10) (1.24) Merbau 0.48 −4.29 a −0.22 d −1.01 d −0.88 d −1.16 d 4.87 (0.32) (1.71) (1.71) (1.25) (1.95) (1.99) (1.78) Santos 1.28 −0.83 d −1.49 c −1.48 d −2.49 d 1.57 d 3.36 rosewood (0.31) (0.66) (1.67) (2.55) (0.86) (0.49) (1.89) Zebrano 1.65 −9.14 a 0.82 d 1.26 d 1.52 d −0.09 d 9.39 (0.62) (1.01) (1.04) (1.18) (1.46) (1.69) (1.08) Wengé 0.67 10.46 a 4.98 a 10.05 a 11.16 a 4.69 b 15.54 (0.35) (2.17) (0.72) (1.87) (1.50) (2.60) (1.55) Padouk 0.95 −6.18 a −5.91 a −8.74 a −9.93 a −5.49 a 12.41 (1.69) (1.32) (0.96) (1.93) (1.46) (2.70) (1.41) Sapelli 3.12 −21.54 a −7.76 a −7.87 a −10.84 a 7.21 a 24.26 (1.15) (0.92) (1.26) (1.52) (1.99) (1.11) (1.52) Iroko 0.20 −15.08 a 1.07 c −2.89 c −2.37 d −4.30 a 15.44 (0.97) (3.76) (0.57) (1.41) (1.49) (0.71) (3.89) Karri 0.69 −3.83 a 0.31 d 0.89 d 0.91 d 0.54 d 4.43 (0.47) (1.37) (1.23) (1.41) (1.81) (0.89) (1.17) Blue gum 0.38 −6.27 a 2.53 a 4.42 a 5.15 a −0.99 d 8.42 (0.21) (2.54) (1.46) (0.88) (1.52) (1.35) (1.91) Maçaranduba 0.08 −1.99 b −5.68 a 1.66 b −2.81 a 13.46 a 6.35 (0.05) (1.21) (0.40) (0.40) (0.38) (1.08) (0.64) Makoré 1.78 −9.43 a −2.44 a −2.45 b −3.33 b 2.35 c 10.19 (1.84) (1.69) (1.37) (1.65) (2.09) (1.28) (2.10) Note: Mean values of colourimetric parameters are from 16 measurements, and of weight losses from 4 specimens. Standard deviations are in italics and parentheses. The t-test analysed the colour changes in relation to the original wood at the 99.9% significance level (a), the 99% significance level (b), the 95% significance level (c), and without an evident significant difference at p ≥ 0.05 (d).

* * The linear correlations between the colourimetric parameters a F,C ab F or hab F versus the lightness * L F for the 21 fungal-attacked tropical woods (Figure4A,C,D) remained almost the same as were determined for the 21 original tropical woods (Figure2A,C,D). Forests 2019, 10, x FOR PEER REVIEW 10 of 14

The linear correlations between the colourimetric parameters a*F, C*ab F or hab F versus the lightness * ForestsL F for2019 the, 1021, 322fungal-attacked tropical woods (Figures 4A, 4C and 4D) remained almost the same10 of as 14 were determined for the 21 original tropical woods (Figures 2A, 2C and 2D).

a*F = 21.63 - 0.22·L*F b*F = 3.54 + 0.33·L*F R² = 0.11 p = 0.151 R² = 0.52 p = 0.000

(A) (B)

C*ab F = 15.57 + 0.15·L*F hab F = 23.85 + 0.77·L*F R² = 0.06 p = 0.921 R² = 0.36 p = 0.058

(C) (D)

Figure 4. Linear correlations between the lightness LL** and the colour coordinates aa**, b b* ((A,A,B B), the colour ** saturation CCabab (C(C), ),and and the the hue hue tone tone angle angle hab (Dhab)—for(D)—for 21 tropical 21 tropical wood woodspecies species attacked attacked by the brown- by the brown-rotrot fungus fungusC. puteana.C. puteana.

In the fungal-attackedfungal-attacked tropical woods, again no evident relationships were found between the 2 2 lightness and redness redness ( (RR2 == 0.11), 0.11), or or the the lightness lightness and and colour colour saturation saturation (R (2R = 0.06).= 0.06). Indirectly, Indirectly, it can it can be bestated stated that that fungal fungal attack attack did did not not have have an an apparent apparent effect effect on on these these relationships. relationships. However, However, due to 2 C. puteana the relationshiprelationship betweenbetween lightnesslightness andand huehue tonetone angleangle evidentlyevidently decreaseddecreased ((RR2 = 0.36 for 2 hab FF—Figure—Figure 4D;4D; while previously RR2 = =0.46 0.46 for for habh—Figureab—Figure 2D).2D). * * Conversely, thethe bb*F coordinate, which indicates yellowing, grewgrew moremore evidentlyevidently withwith LL*FF for the 21 fungal-attacked tropical woods. It is evident from comparing the slope trend B and the coefficient coefficient 2 * * 2 of determination RR2 in FigureFigure2 2BB( (bb* = 11.70 + 0.14 · L*;; B B = = 0.14; 0.14; R2 == 0.10) 0.10) with with the the same same parameters parameters in * * 2 Figure 44BB( (b*FF == 3.54 3.54 + +0.33 0.33 · L·*FL; BF ;= B 0.33; = 0.33; R2 =R 0.52).= 0.52). As the As slope the slope trend trend B increased B increased more more evidently evidently only * onlyfor the for yellow the yellow colour colour coordinate coordinate b*, fromb , from 0.14 0.14 to to0.33, 0.33, there there indirectly indirectly was was confirmed confirmed that that at at brown rot some lighter tropical woodswoods (such(such asas okoumokoumé,é, oror darkdark redred meranti)meranti) obtainobtain aa moremore yellowyellow shade.shade. ∗ The total colour differences ∆ΔEE ab ofof the the fungal-attacked fungal-attacked tropical tropical woods woods were were significantly significantly similar ∗ ∗ ∗ to their their lightness lightness changes changes ∆ΔLL (Figure 5 5A),A),however, however,values valuesof of ∆ΔEE abab were greater as ∆ΔLL in an accordance withwith Equationequation (3)3 (Table (Table 3).3). Usually, Usually, the the lightest lightest and and medium medium light tropical woods okoumokoumé,é, ∗ sapelli, iroko and ovengol ovengol had had the the highest highest ∆ΔEE abab valuesvalues from from 11.28 to 24.26. This This result result is in an accordance with other works dealing with the durability and colour changes of tropical woods due to biological biological deterioration deterioration [48,,49].49]. However, However, it it was simultaneously observed observed that that after attack by C. puteana the top surfaces of wengé wengé and padouk (darker tropical woods—Table 22)) alsoalso hadhad highhigh ∗ values of ∆E ab 15.80 and 12.41 (Table3, Figure5A). This result can be explained by washout of dark extractives presented in darker wood species during the mycological test, similarly mentioned for the Forests 2019, 10, x FOR PEER REVIEW 11 of 14 Forests 2019, 10, x FOR PEER REVIEW 11 of 14  values of ΔE ab 15.80 and 12.41 (Table 3, Figu49e 5A). This result can be explained by washout of dark Forests 2019, 10, 322 11 of 14 valuesextractives of ΔE abpresented 15.80 and in12.41 darker (Table wood 3, Figu49e species 5A). during This the result mycological can be explained test, similarly by washout mentioned of dark for extractivesthe lightness presented changes. in Ondarker the contrary,wood species effects during of the the Δa mycological and Δb values test, of similarly all tropical mentioned species on for the  ∗  ∗  ∗ theΔE lightnesslightnessab value changes.changes. were not OnOn significant the the contrary, contrary, (Figures effects effects 5B, of of5C). the the ∆ aΔaand and∆ bΔbvalues values of of all all tropical tropical species species on on the the∆E ab  ΔE valueab value were were not not significant significant (Figure (Figures5B,C). 5B, 5C). ΔE*ab = 5.92 - 0.50·ΔL* ΔE*ab = 8.70 - 0.16·Δa* ΔE*ab = 8.91 - 0.18·Δb*

ΔE*abR =² 5.92= 0.37 - 0.50· p = 0.003ΔL* ΔE*abR =² =8.70 0.01 - 0.16· p = 0.716Δa* ΔE*abR =² 8.91= 0.01 - 0.18· p = 0.605Δb* R² = 0.37 p = 0.003 R² = 0.01 p = 0.716 R² = 0.01 p = 0.605

(A) (B) (C) (A) (B)  (C) Figure 5. Linear correlations between the total colour difference E ab and changes of other colour * * *  ∗ FigureparameterFigure 5. Linear 5. LinearL correlations(A), correlations a (B )between, b between(C)—for the thetotal 21 total colour tropical colour difference woods difference attacked E ∆ab Eandab with andchanges changesthe brown-rotof other of other colour fungus colour parameterC.parameter puteana. L * ∆(AL*), (Aa),* (∆Ba)*, (Bb),* (∆Cb)—for* (C)—for 21 tropical 21 tropical woods woods attacked attacked with with the the brown-rot brown-rot fungus fungus C. puteana.C. puteana. Several studies have shown that there are some relationships between the colour parameters of woodSeveral Severaland studiesits studiesdecay have resistance have shown shown [that15, that16 there,46 there– 50are]. aresomeThe some relationship relationships relationships between between between the the colour thecolour colour and parameters weight parameters loss of of of wooddecayedwood and and itswood decay its decayis basedresistance resistance on the [15 type, [1615,, 46and16–,4650 amount–].50 The]. The relationship of relationshipwood extractives, between between thewhich thecolour have colour and effect and weight on weight the loss colour, loss of of decayedanddecayed on wood its wood decay is based is resistance. based on the on thetype Such type and relationships andamount amount of woodcould of wood extractives,be encouraging extractives, which which but have not have effect always effect on thesufficient on colour, the colour, for andpredictingand on its on decay its decay decay resistance. resistance resistance. Such of Suchtested relationships relationships woods. Specifically,could could be encouraging be from encouraging our experiment but butnot notalways it always is evidentsufficient sufficient that for for for  predicting21predicting tropical decay woods decay resistance resistanceno dependency of oftested tested was woods. woods. found Specifically, between Specifically, the from fromtotal our ourcolour experiment experiment difference it itis ΔE is evident evidentab and thatthe that decayfor for 21  ∗ 21 resistancetropicaltropical woods woods determined no no dependency dependency as weight was loss was found  foundm (Figure between between 6; R the2 = the 0.10).total total colour colour difference difference ΔE∆abE andab and the thedecay decay 2 resistanceresistanceGenerally, determined determined the intensity as weight as weight and loss specificity loss m ∆(Figurem (Figure of colour 6; R62; =R changes0.10).= 0.10). in woods attacked by brown rot—when browningGenerally,Generally, can the be theintensity connected intensity and and with specificity specificity yellowing of colour of or colour bluing changes changes and in woods also in woods with attacked reddeningattacked by brown by or brown greening—are rot—when rot—when browninginfluencedbrowning can not can be only connectedbe connected by the enzymatic with with yellowing yellowing and pigment or bluing or bluing specification and and also also with of withthe reddening individual reddening or brown-rot greening—are or greening—are fungus, influencedbutinfluenced also notby nottheonly onlywood by the by species theenzymatic enzymatic (e.g. andpresence and pigment pigment of specificspecification specification extracts), of the of the theindividual degree individual of brown-rot its brown-rot decay, fungus, and fungus, the butenvironmental butalso also by bythe thewood factors. wood species Therefore, species (e.g. (e.g., presence some presence of oftested specific of specifictropical extracts), extracts),woods the at thedegreeexposition degree of its ofto decay, itsC. decay,puteana and and hadthe the a environmentalmoreenvironmental yellowish factors. factors.shade Therefore, while Therefore, other some ones some of a of moretested tested reddish tropical tropical shade, woods woods when at expositionexposition all the colour totoC. C. changes puteana puteana dependedhad had a morea moreprobablyyellowish yellowish on shade their shade molecular while while other other structure onesones aa moreand natural reddish reddish durability. shade, shade, when when In futureall all the the experiments,colour colour changes changes we depended would depended like probablytoprobably analyse on ontheirthese their molecularfactors molecular in morestructure structure detail. and and natural natural durability. durability. In In future future experiments, experiments, we we would would like like to to analyseanalyse these these factors factors in in more more detail. detail.

ΔE*ab = 7.57 + 1.02·Δm

ΔE*abR² = 7.57= 0.10 + 1.02·p = 0.166Δm R² = 0.10 p = 0.166

∗ Figure 6. Linear correlations between the total colour differences ∆E ab and the weight losses ∆m of 21 tropical woods exposed 6 weeks to C. puteana.

Forests 2019, 10, 322 12 of 14

Colour changes of tropical woods exposed in interiors of buildings are unwanted. Brown-rot fungi decrease their strength and can worsen their colour and aesthetic. On the contrary, some benefits of rotting can be interesting for claddings and other decorative products, but in this situation the intentional decay has to be performed before they are installed. By processing spalted wood artists can create decorative material, such as fine art mosaics, furniture, and dishes, which have been used for centuries [51] and also hold an interesting niche modern market in decorative veneers or other decorative materials in North America and Europe [17].

4. Conclusions Several tropical woods have positive surface characteristics, such as interesting texture and colour, and high natural durability, which is an essential requisite for wooden constructions exposed to the environment with a high risk of biodeterioration by fungi and insects. For architects, changes in their original colour at biodeterioration processes are important. The colour analyses of 21 tropical woods before and after intentional attack by the brown rot-fungus C. puteana led to the following conclusions:

• For the original tropical woods, the a* coordinate (redding) declined with increase of the lightness * * * L , while the b (yellowing) and h ab (hue ton angle) coordinates grew with the lightness. No * * significance was found between C ab (colour saturation) and L . • For the fungal-attacked tropical woods, the linear correlations between the colour coordinates * * * a , C ab or hab and the lightness L remained almost the same as for the original tropical woods, and only the b* coordinate grew more evidently in relation to L*. ∗ • The total discoloration ∆E ab values were highest for the top surfaces of the lighter species (sapelli, ∗ okoumé, iroko) and the darkest species (wengé), when the ∆E ab were justified by the marked change of the lightness ∆L*. • Significant changes in the lightness and colouration of the fungal-attacked tropical woods indicated these colour changes could be caused not only by the biodegradation of polysaccharides, but also by biodegradation or leaching of some extractives during laboratory mycological tests.

Author Contributions: For research articles with several authors, a short paragraph specifying their individual contributions must be provided. The following statements should be used “conceptualization, Z.V. and L.R.; methodology, Z.V. and L.R.; software, Z.V. and L.R.; validation, Z.V. and L.R.; formal analysis, Z.V. and L.R.; investigation, Z.V. and L.R.; resources, Z.V. and L.R.; data curation, Z.V. and L.R.; writing—original draft preparation, Z.V. and L.R.; writing—review and editing, Z.V. and L.R.; visualization, Z.V.; supervision, L.R..; project administration, L.R. Acknowledgments: This work was supported by the Slovak Research and Development Agency under the contract No. APVV-17-0583, and the VEGA project 1/0729/18. Conflicts of Interest: The authors declare no conflicts of interest.

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