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European Journal of Applied Sciences – Vol. 13, No. 1
Publication Date: February 25, 2025
DOI:10.14738/aivp.131.18176.
Sahin, C. K., & Merdan, R. (2025). Surface Behaviors of Pine Wood (Pinus nigra) After Short-Term Weathering: Urban Furniture
Suitability Investigation. European Journal of Applied Sciences, Vol - 13(1). 98-109.
Services for Science and Education – United Kingdom
Surface Behaviors of Pine Wood (Pinus nigra) After Short-Term
Weathering: Urban Furniture Suitability Investigation
Candan Kus Sahin
Suleyman Demirel University, Architecture Faculty,
Department of Landscape Architecture Isparta, Turkiye
Rahim Merdan
Isparta University of Aplied Sciences, Keçiborlu Vocational School,
Department of Interior Design, Isparta, Turkiye
ABSTRACT
The tangential/radial ratio (T/R) has usually been used to investigate wood’s
physical properties due to moisture uptake and loss differences. In this issue, the
color coordinate differences were evaluated between two surfaces for Black pine
(Pinus nigra). Initially (controls), it was measured to be a (T-R) L*: 10.71
1.45 (metric) difference for lightness, (T-R) a*: -0.07 (metric) for a* coordinate,
and (T-R) b*:- 0.14 (metric) for the b* coordinates. However,the total color changes
(discoloration) of two surfaces were found to be after outdoor exposure, separately.
The tangent surface shows ΔET: 10.71 (metric), which is higher than the radial
surface values of ΔER: 8.57 (metric) after weathering. The chroma and hue
differences were observed to be negligible for control and weathered samples, with
only <2.0 units differences for both surfaces. A similar trend was also observed for
gloss properties: all gloss differences were found to be <3.0 Gu which could not be
visually differentiated easily. The radial surface seemed to have a higher
yellowness value than tangent surfaces, which was found to be YIR: 52.70 (numeric)
for radial surfaces and YIT: 47.62 (numeric) for tangent surfaces. After weathering,
considerably lower X-(red), Y-(yellow) and Z-(blue) stimuli values were
calculated: ΔXT(w-c):-12.68 (numeric) in tangent and ΔXR(w-c): -10.67
(numeric) in radial surface for X stimuli, ΔYT(w-c): -12.47 (numeric) in tangent- and ΔXR(w-c): -10.46 (numeric) in radial surface for Y stimuli; and ΔZT(w-c): -
7.28 (numeric) for tangent and ΔZR(w-c): -7.42 (numeric) in radial surface for Z
stimuli, respectively.
Keywords: Black pine, urban furniture, tangent and radial surface, weathering,
discoloration.
INTRODUCTION
Furniture could be categorized as places where it is used for either indoor- or outdoor
applications [1]. However, urban and street furniture are generally seen as the same terms,
and both are used for similar meanings. In general, the urban furniture stands for open space,
and it is used by the public [2, 3]. The urban space offered many ways of using the ambient
equipment in compliance with a high standard of life quality for the city inhabitants [2, 4].
However, numerous types of urban furniture can be made from a variety of materials, providing
a leisurely, pleasant, dynamic or relaxing atmosphere with comfort. Some of the common
examples ofthose objects are sidewalks, parking elements, benches, bus stops, streetlights, sign
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Sahin, C. K., & Merdan, R. (2025). Surface Behaviors of Pine Wood (Pinus nigra) After Short-Term Weathering: Urban Furniture Suitability
Investigation. European Journal of Applied Sciences, Vol - 13(1). 98-109.
URL: http://dx.doi.org/10.14738/aivp.131.18176
boards, bike racks, plant boxes, tables, signage, litter bins, shelters, streets, playground
equipment's, and so on [5 6]. Due to those diversities, there are many ways to categorize urban
furniture [1].
The diversity of materials could be useful for urban furniture objects that create an enjoyable
atmosphere, can serve a function, be aesthetic or both [3, 4]. As a result of technological
developments, the many of natural or artificial elements, such as ceramics, glass, metal,
concrete, plastic, wood, and synthetic polymers, could be useful for urban furniture
manufacturing [7, 8]. However, appearance is a very important characteristic, influencing some
physical or psycho-emotional effects [3, 4, 8]. It is important to note that the urban spaces are
accessible to all types of users, including children, youth, disabled or elderly users
[4]. Therefore, open space designers must take into account the diverse user groups interacting
with those established urban furniture elements. Because the presence of inadequate objects,
such as uncomfortable seating, a dissatisfying view, or an unwanted odor from nearby, could
have a negative experience for users [9]. On the other hand, those negative impacts could be
overcome by selecting a good place to establish with proper elements made from suitable
materials. Regarding those issues, wood is usually suggested to be one of the best choices for
urban furniture manufacturing [3, 10]. Besides its sustainability and pleasant natural colors, it
is also an easier-to-work with and more cost-effective material than many other materials (e.g.,
concrete, steel, ceramic). There are numerous reports on the advantages of using wooden
objects in architectural design practices, which could be found further information
elsewhere [3, 10-12].
Typically, wood has a pleasing visual appearance that is expected to fulfill the aesthetic
requirements for open-space designs. Therefore, general wood surface textures such as color,
grain and lust are some of the important properties for the attractive appearances in urban
furniture applications [11]. However, the wood property classification relies on qualified
design professionals that analyze texture patterns and characteristics on timbers, which could
be a difficult task. In this case, a good knowledge of this topic of determining and using certain
species and plane directions of wood is helpful for sustainability and effective utilization of
wood.
The wood surfaces are not uniform, since they are composed of different types of cells and
regions (e.g., late wood-early wood, sapwood-heartwood). Those variations cause color
differences even among the same wood species [13]. Regarding this heterogeneity, when wood
is exposed to outdoor environments, the natural color changes at different rates for different
surfaces of the same wood pieces under similar conditions [11, 14]. In wood, knowledge of
stiffness, strength, toughness and aesthetic properties is of primary importance to customers,
manufacturers and designers. However, the relationship between the strength and aesthetic
properties of wood has received a great deal of attention in the architectural context. On the
other hand, the different surface behaviors of wood have been somewhat neglected,
particularly in the context of urban furniture applications [7, 10, 15]. While some limited
research has been done in the areas of strength and toughness properties, for the surface
deformations of wood along or across the grains in anatomical things, very little systematic
work has been conducted in terms of physicochemical properties [3, 7, 10]. But the tensile
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European Journal of Applied Sciences (EJAS) Vol. 13, Issue 1, February-2025
stresses at different directions of planes may lead to more cracking or splitting in one direction
than another, which could lead to the failure of wooden objects as urban furniture functions.
The aim of this study is to evaluate the variability of Black pine wood (Pinus nigra) color before
and after outdoor exposure. The tangent and radial surfaces of the same wood species were
investigated, comparatively, regarding their appeal as urban furniture material.
MATERIAL AND METHODS
A specially prepared, a softwood species of Black pine (Pinus nigra) was selected for the
experiments. The boards were supplied from a local market, Isparta-Turkiye and small samples
were cut into 50 mm x 50 mm x 10 mm pieces and conditioned at 20°C and 65 % relative
humidity to reach an air-dry moisture content of 12%. The natural outdoor exposure
(weathering process) was conducted on the south side of a park (Cunur Park) located in
Isparta-Turkiye. The specially prepared tangent and radial apparent samples were aged
outdoors for six months, during which the optical measurements were taken before outdoor
exposure (as a control) and after for radial and tangent surfaces, respectively. The total of 20
specimens were used for conducting this research.
The discoloration of wood specimens was determined using a color spectrophotometer (X-Rite
SP 968 Spectrophotometer). Measurements were made using standard illumination and a
standard observer. The CIE L*a*b* (CIE, 1976), where L* stands for lightness, a* stands for
redness-greeness, and b* stands for yellowness-blueness, was used to quantify the changes in
color. The total color changes (ΔΕ*) were determined with using the following equation:
2 2 2 1/2 ΔΕ* = [(ΔL*) + (Δa*) + (Δb*) ]
[1]
Where: ΔL*, Δa* and Δb* are the changes in the color coordinates L*, a* and b* for the respective
time intervals.
Δh stated color hue difference values, with respect to color coordinate values (L*a*b*) and
chromacity (C*).
Δh*ab = [(ΔE*ab)2-(ΔL*)2-(ΔC*ab)2]1⁄2 [2]
A positive sign indicates a counterclockwise change of hue, a negative sign indicates a clockwise
change in color space.
The CIE XYZ (1931) tristimulus method was also used to evaluate color changes, where X
stimuli stand for red, Y stimuli stand for yellow, and Z stimuli stand for blue. Yellowness is
associated with a general product degradation by light, chemical exposure, and processing.
Yellowness indices are used mainly to measure these types of degradation. In this regard, the
yellowness index (YI) was found according to the ASTM Method E313 standard, which is
calculated as follows:
YI: (100(CxX - CzZ))/Y [3]