Alder Wood Research Articles

Effect of delignification pretreatment and furfurylation on practical properties of alder wood (Alnus spp.)

Partial delignification of alder wood specimens was performed with alkaline sulfite and peracetic acid (PAA) methods, and subsequently the delignified samples were saturated with furfuryl alcohol, as an eco-friendly chemical. The aim of delignification before furfurylation was to facilitate the penetration of furfuryl alcohol into the cell wall, in order to overcome the weak mechanical properties and hydrophilicity of alder wood as a fast growing species. The results showed that alkaline delignification removed a lower percentage of lignin despite more significant mass loss as compared to peracetic acid delignification method, which indicates more carbohydrates degradation in alkaline delignification. Infrared spectroscopy also confirmed more retention of carbohydrates in the sample delignified with peracetic acid. The polymerization of furfuryl alcohol in the cell cavities decreased the access of water molecules to the hydroxyl groups of the cell wall, increased the contact angle, and decreasing surface wettability. This effect was more noticeable in the PAA-delignified samples. Mechanical tests revealed that the delignified samples with peracetic acid had higher mechanical strength and modulus, compared to the alkaline sulfite delignified samples. This was attributable to the maintenance of carbohydrates during the delignification process.

Take a handful of nuts in a bowl! Turned wooden vessel with hazelnuts from Czarnówko against the background of other finds from cemeteries of the Wielbark culture

Abstract In 2009, during research of a cemetery of the Wielbark culture in Czarnówko (Lębork District, Pomerania), an inhumation grave was discovered, which contained the remains of a wooden bowl with copper alloy fittings. Inside it, several hazelnuts were preserved. This vessel, in the light of the analysis carried out, was made of alder wood using a turning technique. Discoveries of this type are not only rare in the area of the Wielbark culture, but also in the rest of Central European Barbaricum. This article presents the results of the archaeobotanical research and demonstrates the bowl in the broader context of Roman Period discoveries.

Acetylation of Aspen and Alder Wood - Preliminary Tests

An experimental study of the physical and mechanical properties of untreated and acetylated wood was conducted. The effect of acetylation on wood density was investigated. It was established that the density of the samples generally decreases after acetylation. As the level of acetylation increases, the fiber saturation point decreases in both conifers and hardwoods. Acetylation of wood helps to reduce the sorption properties of wood. The amount of swelling was analyzed. For untreated wood (aspen and alder), the volume swelling index is at the level of 7.5 %. Acetylation contributes to the stability of the geometric dimensions of structures, as the volume swelling index for aspen decreased by 4 times, for alder – by 2 times. An increase in the amount of swelling along the fibers is observed in all samples. Regarding the nature of the destruction of the samples during compression, the aspen (both untreated and acetylated) only crumples without visible signs of destruction. In some samples of alder, partial exfoliation is visible. It was found that acetylation has an ambiguous effect on the mechanical properties of wood of both species.

Burning Properties of Combined Glued Laminated Timber

This study delved into the combustion properties of combined glulam bonded using polyurethane (PUR) and resorcinol-phenol-formaldehyde (RPF) adhesives. The experiment involved three distinct wood species, namely, spruce, alder, and beech, which were combined in homogeneous, non-homogeneous symmetrical, and non-homogeneous asymmetrical arrangements. These species were selected to represent a spectrum, namely, softwood (spruce), low-density hardwood (alder), and high-density hardwood (beech). The varying combinations of wood species illustrate potential compositions within structural elements, aiming to optimize mechanical bending resistance. Various parameters were measured during combustion, namely, the heat release rate (HRR), peak heat release rate (pHRR), mass loss rate (MLR), average rate of heat emission (ARHE), peak average rate of heat emission (MARHE), time to ignition (TTI), and effective heat of combustion (EHC). The findings indicate that incorporating beech wood into the composite glulam resulted in an increase in heat release, significantly altering the burning characteristics, which was particularly evident at the second peak. Conversely, the use of spruce wood exhibited the lowest heat release rate. Alder wood, when subjected to heat flux at the glued joint, displayed the highest heat emission, aligning with the results for EHC and MARHE. This observation suggests that wood species prone to early thermal decomposition emit more heat within a shorter duration. The time to ignition (TTI) was consistent, occurring between the first and second minute across all tested wood species and combinations. Notably, when subjected to heat flux, the glulam samples bonded with PUR adhesive experienced complete delamination of the initial two glued joints, whereas those bonded with RPF adhesive exhibited only partial delamination.

Structure and properties of biomorphic carbon scaffolds based on pressed birch and alder wood

The effect of prepressing of birch and alder wood on the pyrolysis process, structure and properties of biocarbon scaffolds were investigated. It is shown that after pressing process, internal stresses in the wood are preserved, which leads to a change in shrinkage during pyrolysis, especially in the pressing direction. The limitation of the samples expansion in the pressing direction made it possible to increase the density of biocarbon scaffolds (up to ∼ 1 g/cm3) and to obtain a linear dependence of their density on the density of compressed wood. Deformation of wood did not lead to a noticeable change in the atomic structure of biocarbon, but defects in the cell walls that affect the electrical resistivity of the biocarbon scaffolds were formed. The bending strength of biocarbon samples based on compressed wood was primarily determined by their density and weakly depended on the particular species. The obtained strength values were not inferior to the published data, which indicates that the defects formed during deformation were not stress concentrators.

Determination of color properties of mahogany, mulberry and alder woods after exposure to various harmful organisms growing in the soil

Her ağaç türü farklı yapısal özelliklere sahip olduğundan dolayı, aynı aktif toprak ortamında bulunan ve bu ortamda gelişen çeşitli zararlı organizmalara karşı farklı bir direnç özelliği sergilemektedir. Bu çalışmada, dut, maun ve kızılağaç odunlarına ait olan deney örnekleri aktif olarak bulunan bir toprak ortamına yerleştirilmiş olunup, 12 hafta süreyle toprağa maruz bırakılmıştır. Belirtilen bu süre tamamlandıktan sonra, deney örnekler topraktan çıkarılmıştır. Daha sonra numuneler suyla yıkanmış olunup, devamında bir fırında kurutma işlemine tabi tutulmuştur. Daha sonra deney örnekleri üzerinde renk parametrelerine ait olan ölçümler yapılmıştır. Elde edilen sonuçlara göre, b*, L*, C*, a* ve ho parametreleri için varyans analizi sonuçları anlamlı olarak elde edilmiştir. Toplam renk farkı değerlerinde ise en düşük kızılağaçta ∆E*: 11.54 olarak elde edilirken, maun odununda ∆E*: 18.11 ve dut ahşabında ∆E*: 19.07 olarak bulunmuştur. Her üç ağaç türü için aktif toprağa maruz kalması sonrasında L*, a*, b* ve C* değerlerinin azaldığı görülmüştür. h açısı değerinde ise maun ve kızılağaç odunlarında artışlar görülmüş, dut odununda ise azalmalar elde edilmiştir. Yapılan toprak testinin ahşap malzemelerin yapısal özellikleri ile sahip oldukları doğal renginde değişikliklere sebep olduğu görülmüştür.

Evaluation of Regional Elevation and Blade Density Effects on the Efficiency of a 1-kW Wind Turbine for Operation in Low-Wind Counties in Iran

This research investigates the effect of blade density and elevation above sea level on the startup time (Ts) and power coefficient (Cp) of a 1-kW two-bladed wind turbine. The study uses three Iranian hardwoods as the blade material and four counties of Iran with low wind speeds and different elevations as the case studies. The BW-3 airfoil is considered as the blade profile. A multi-objective optimization process with the aid of the differential evolution (DE) algorithm is utilized to specify the chord length and twist angle. The findings demonstrate that, while the maximum Cp of the optimal blades designed with all three types of wood is high and equal to 0.48, the average Ts of the optimal blades designed with oak and hornbeam wood is 84% and 108% higher than that of alder wood, respectively. It is also observed that, while raising the elevation to 2250 m decreases the Cp by only 2.5%, the ideal blade designed to work at sea level could not manage to start rotating at a height of 1607 m and above. Finally, an improvement in the Ts and Cp was observed by performing optimization based on the local atmospheric conditions associated with the incrementing blade chord length at high elevations.

Copper-nitrogen dual-doped activated carbon derived from alder wood as an electrocatalyst for oxygen reduction

In the present study, unmodified nitrogen-doped carbon material (N-doped C) and modified with copper nanoparticles (CuNPs) nitrogen-doped carbon material (Cu-N-doped C) have been synthesized using wood biomass as a carbon precursor, dicyandiamide as a nitrogen precursor, and anhydrous copper acetate as the precursor of Cu. The morphology, structure, and chemical composition of the obtained materials have been analyzed by performing nitrogen sorption experiments and described using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and scanning-electron microscopy (SEM). The electrocatalytic performance of N-doped C and Cu-N-doped C materials has been evaluated for the electro-reduction of oxygen (ORR) in alkaline media using linear scan voltammetry (LSV) and the rotating disk and ring-disk electrode (RDE and RRDE) methods.It has been determined that the nitrogen-doped carbon material and that modified with CuNPs have been synthesized with graphene-like structures and especially high specific surface areas of 2631 m2 g−1 and 2243 m2 g−1, respectively. The onset potential (Eonset) and half-wave (E1/2) potential values are approximately 0.921 V and 0.828 V, respectively, for the N-doped carbon with the loading of 0.0889 mgcat cm−2 and 0.975 V and 0.843 V, respectively, for Cu–N-doped carbon (0.4044 mgcat cm−2), comparable with the commercial Pt/C catalyst.

Chip grain size from the process of machining steamed and unsteamed alder wood on a cnc machining center and assessment of separation results

The paper discusses the particle size of the chips formed in the process of machining unsteamed and steamed alder wood on a CNC machining center. From the granulometric analysis of the chips, it follows that the average share of the coarse fraction of the chips created from unsteamed alder wood is 66.0% and steamed alder wood is 62.9%. The representation of medium-coarse fractions of alder wood with dimensions of 1.0-0.125 μm in unsteamed wood is 29.5% and steamed by 32.7%. Dust fractions with dimensions below 125 μm in unsteamed alder wood account for 4.5% and in steamed alder wood 4.4%. Chips of non-steamed or steamed alder wood with dimensions below 32 μm were not measured, so it can be concluded that no respirable dust particles with dimensions below < 10 μm are formed. Changes in the physical and mechanical properties of steamed alder wood are manifested by a decrease in the coarse fraction above 2 mm and an increase in the fraction of chips 0.125 to 2000 μm. For the separation of chips, both unsteamed and steamed alder wood, from the transport air, fabric filters and filter fabric Finet PES 4 are suitable, the separation limit of which is smaller than the size of the smallest chips formed in the milling process: aMO = 7 m <<< amin = 32 m.

Effect of Low-Thermal Treatment on the Particle Size Distribution in Wood Dust after Milling.

The thermal treatment of wood can improve the appearance of the wood product's surface, its dimensional stability, and resistance to fungal attacks. However, the heat treatment changes the technological properties of wood, making it a new engineering material. This work investigates the effect of the low-thermal treatment of birch wood (Betula pendula Roth.), European beech wood (Fagus sylvatica L.), and alder wood (Alnus glutinosa L.) on the fine dust particles creation during woodworking. The samples of thermally treated wood with temperatures commonly used for the change of wood colour (105, 125, and 135 °C) were compared with reference samples made of natural wood. All 12 variants of the tested woods were milled using the 5-axis CNC machining center (20 mm diamond cutter, rotational speed 18,000 rev·min-1, the depth of cut 3 mm, feed rates of 2, 4 and 6 m∙min-1). A sieving analysis method allowed measuring the dust particle size distributions in all dust samples. The experiment's result analysis points out that wood type, thermal treatment, and feed rate meaningfully affect the size distribution of dust particles. Compared to birch wood and beech wood, the milling of alder wood samples created a much higher content of the finest dust particles, with particle sizes smaller than 0.032 mm. Increased temperatures in thermal treatment increase the share of fine dust particles with sizes smaller than 0.125 mm, compared to wood in its natural state. Milling with a lower feed rate (2 m·min-1) creates finer dust than processing with higher feed rates (4 and 6 m·min-1). Generally, the milling of alder in a natural or thermally treated state is a source of fine dust particles, particularly at low feed speed-rate milling, compared to birch and beech wood. In general, these results indicate that the low temperature thermal treatment parameters attribute new technological properties to all thermally modified types of wood tested.

A Comparison of Artificial Neural Network and Time Series Models for Timber Price Forecasting

The majority of the existing studies on timber price forecasting are based on ARIMA/SARIMA autoregressive moving average models, while vector autoregressive (VAR) and exponential smoothing (ETS) models have been employed less often. To date, timber prices in primary timber markets have not been forecasted with ANN methodology. This methodology was used only for forecasting lumber futures. Low-labor-intensive and relatively simple solutions that can be used in practice as a tool supporting decisions of timber market participants were sought. The present work sets out to compare RBF and MLP artificial neural networks with the Prophet procedure and with classical models (i.e., ARIMA, ETS, BATS, and TBATS) in terms of their suitability for forecasting timber prices in Poland. The study material consisted of quarterly time series of net nominal prices of roundwood (W0) for the years 2005–2021. MLP was found to be far superior to other models in terms of forecasting price changes and levels. ANN models exhibited a better fit to minimum and maximum values as compared to the classical models, which had a tendency to smooth price trends and produce forecasts biased toward average values. The Prophet procedure led to the lowest quality of projections. Ex-post error-based measures of prediction accuracy revealed a complex picture. The best forecasts for alder wood were obtained using the ETS model (with RMSE and MAE values of approx. 0.38 € m−3). ETS also performed well with respect to beech timber, although in this case BATS was just as good in terms of RMSE, while the difference between ETS and neural models amounted to as little as 0.64 € m−3. Birch timber prices were most accurately predicted with BATS and TBATS models (MAE 0.86 € m−3, RMSE 1.04 € m−3). The prices of the most popular roundwood types in Poland, i.e., Scots pine, Norway spruce, and oaks, were best forecasted using ANNs, and especially MLP models. Among the neural models for oak (MAE 4.74 € m−3, RMSE 8.09 € m−3), pine (MAE 2.21 € m−3, RMSE 2.83 € m−3), beech (MAE 2.31 € m−3, RMSE 2.70 € m−3), alder (MAE 1.88 € m−3, RMSE 2.40 € m−3), and spruce (MAE 2.44 € m−3, RMSE 2.58 € m−3), the MLP model was the best (the RBF model for birch). Of the seven models used to forecast the prices of six types of wood, the worst results were obtained for oak wood, while the best results were obtained for alder.

Identification of Alnus incana (L.) Moenx. × Alnus glutinosa (L.) Gaertn. Hybrids Using Metabolic Compounds as Chemotaxonomic Markers

Alnus glutinosa (L.) Gaertn. and Alnus incana (L.) Moenx. grow naturally in Lithuania, and their ranges overlap. They are considered ecologically and economically important species of forest trees. The objective of our study was to determine plant bioactive compounds, such as total phenolic (TPC) and flavonoid compounds (TFC), in the wood of alders and their hybrids in order to specify the opportunity to use secondary metabolites (SM) for the identification of alder hybrids. The samples from juvenile and mature alder woods (n = 270) were collected at three different sites in the natural forests of Lithuania. The TPC and TFC content was determined using spectrophotometric methods and was expressed in mg/g of fresh mass. Obtained results showed that the TPC of A. incana was statistically higher compared to A. glutinosa; however, in hybrid alder wood it was intermediate. The TFC was statistically higher in hybrid alder wood and lowest in A. glutinosa. The TFC was higher in mature trees; however, the TPC showed the opposite tendency. In our case, the TPC was higher in continental sites, while TFC was higher in mature alders at costal sites. Obtained data allow us to assume that TPC and TFC in alder wood can be used as taxonomic markers. This study expanded the knowledge of alder physiology and contributed to the identification of alder hybrids. The correct identification of tree species is very important for the conservation of natural resources and for the sustainable use of higher value-added products.

CUCUJUS CINNABERINUS (SCOPOLI, 1774) (COLEOPTERA: CUCUJIDAE) IN ROSCI0045 CORIDORUL JIULUI, ROMANIA

The protection of the Natura 2000 species Cucujus cinnaberinus (Scopoli, 1774), protected by Romanian and European legislation, requires knowledge of distribution, threats and conservation status. In Romania the species is protected in only 9 Natura 2000 areas of the 442 SCI declared until 2021. All the protected areas in which the species is mentioned are located along the Carpathian Arch except ROSCI0135 Pădurea Bârnova – Repedea located in the Central Moldavian Plateau. The identification of the species in ROSCI0045 Coridorul Jiului brings new data about the distribution of the species and its conservation status. Observations on the species in larval stage were made by direct searches in specific habitats in the protected area. In the months of May, August and September 2022, Cucujus cinnaberinus was identified in several points along the protected area: Dăbuleni on poplar wood in the Danube River meadow, Foișor on poplar wood in the Jiului meadow, Bratovoești in ploplar wood of the former channels of the meanders Jiului River, Calopăr on ash wood from the Dâlga valley and Turburea on alder wood in the Gilortului meadow. The identification of Cucujus cinnaberinus Natura 2000 species requires further monitoring at the site and the implementation of appropriate protection and conservation measures.

Emissions of CO2 from downed logs of different species and the surrounding soil in temperate forest

The decomposition of deadwood plays a very important role in the functioning of the forest ecosystem. The present study was conducted with the objectives to: (1) determine the amount of deadwood respiration depending on species and degree of decomposition; (2) determine the extent of the impact of decomposing wood on the amount of respiration in surrounding soil; (3) find a relationship between the amount of respiration and the chemical fractional composition of soil organic matter. Our research has shown that respiration of decaying wood samples was 2-3 times lower compared to soil, regardless of the type of wood and the degree of wood decomposition. The conducted analyses confirmed the influence of the species of wood and the degree of decomposition on the respiration rate in wood samples. More decomposed wood (4th and 5th degree of decomposition) releases more CO2 compared to less decomposed wood and the highest CO2 emissions were recorded for aspen and alder wood. Better understanding of the mechanisms and factors affecting CO2 emissions in forest ecosystem can help reduce climate change.

The Effect of Different Moderate Thermal Modification Durations on the Wood Properties of American Alder

To investigate the effect of moderate thermal modification (TM) on wood properties, American alder (Alnus rubra) wood was treated at 140 °C for 4 h, 8 h and 13 h, the physical and mechanical properties, dimensional stability and color changes of wood were compared and studied. The results showed that the absolute dry density of moderate-TM wood decreased significantly with time except for the 4 h treatment. Moderate TM can significantly reduce the residual stress of wood up to 90.3%. There were no significant differences in MOR and MOE between most moderate TM wood and the control group; moderate TM decreased the moisture absorption and water up-taking of wood significantly; compared to the control group, the swelling of TM wood for 13 h decreased by 24.2% and 16.0% in the tangential and radial direction, respectively, showing a significant improvement in dimensional stability. There were almost no color changes even when wood endured 140 °C and 13 h TM. The moderate TM at 140 °C for 13 h can efficiently improve wood dimensional stability and retains the natural color of wood while causing almost no damage to the wood's mechanical strength.

Microwave-assisted synthesized renewable carbon nanofiber/nickel oxide for high-sensitivity detection of H2O2

• Preparation of high activity CNFs/NiO via microwave conversion of alder wood. • First report on preparation of renewable CNFs/NiO for high-sensitivity detection of H 2 O 2 . • The sensitivity of CNFs/NiO electrode can reach 304.2 µA cm −2 mM −1 . • The catalytic mechanism analysis for high-sensitivity detection of H 2 O 2 by renewable CNFs/NiO. In the present study, carbon nanofibe (CNFs) with a highly defective structure were prepared via microwave pyrolysis of H 2 O 2 activated alder wood. The nickel oxide nanoparticles (NiO NPs) were anchored on the surface of the carbon nanofibers with the aid of microwave hydrothermal treatment. The electrochemical reactivity of the carbon nanofiber/nickel oxide electrode was evaluated for nonenzymatic H 2 O 2 detection and exhibited a fast response speed (within 1 s), high sensitivity (304.2 µA cm −2 mM −1 ), wide linear working range (0.1 µM to 3489.9 µM), low detection limit (0.57 µM), and good reproducibility, anti-interference and stability. For tap water, the prepared electrode was shown the recovery and RSD of H 2 O 2 between 94.7 and 98.9 % and 2.6–5.4 %, respectively as well the recovery and RSD of H 2 O 2 in river water samples reached 101.2–104 % and 2.8–4.7 %, respectively. The catalytic mechanism of hydrogen peroxide by using the prepared carbon nanofibers/nickel oxide was analyzed.

The effect of microwave treatment on the gloss resistance of varnishes in some tree species

Bu çalışmada ülkemizde ticari önemi olan ağaç türleri odunların da mikrodalga işlemi ile verniklerin parlaklık özellikleri üzerine etkileri araştırılmıştır. Odun ile yüzey işlem maddeleri arasındaki etkileşimin belirlenmesi, odun özelliklerinin iyileştirilmesi ve farklı kullanım yerleri için uygunluklarının belirlenerek ortaya konulması oldukça önemlidir. Bu amaçla 3 farklı ağaç türü; yapraklı ağaç türlerinden doğu kayını (Fagus orientalis) ve sakallı kızılağaç (Alnus glutinosa subsp. Barbata.) ile iğne yapraklı ağaç türlerinden doğu ladini (Picea orientalis) ve vernik türlerinden selülozik vernik, poliüretan vernik kullanılmıştır. Selülozik vernik için liflere paralel ve liflere dik yönde parlaklık değerleri incelendiğinde kayın odunu en düşük parlaklık değerine sahipken, en yüksek parlaklık ise kızılağaç odununda belirlenmiştir. Poliüretan vernik için ağaç türleri hem liflere dik hem de liflere paralel yönde parlaklık üzerine ele alındığında bir fark bulunamamıştır. İşlem türü olarak poliüretan vernik için 90 s’lik mikrodalga olumsuz etki göstermiştir. Ağaç türlerinde parlaklık değerlerinde 90 s’lik mikrodalga uygulamasının parlaklık değerlerini azalttığı tespit edilmiştir. Sonuç olarak; mikrodalga uygulaması verniklerin parlaklık özelliklerini etkilediği belirlenmiştir.

Influence of Pine and Alder Woodchips Storage Method on the Chemical Composition and Sugar Yield in Liquid Biofuel Production.

The aim of this study was to investigate the effect of storing methods of woodchips from two species, pine (Pinus sylvestris L.) and alder (Alnus Mill.), on the basic chemical composition and sugar yield in liquid biofuel production. Two methods of storing woody biomass were used in the study—an open pile and a cover pile. The wood was felled at the end of November and was stored as industrial chips for eight months from December onward. After this time, material was collected for chemical composition analyses and enzymatic hydrolysis. The results of the chemical composition analysis of the wood for both studied species showed the influence of the type of storage on the composition of the individual structural components of the wood. Based on the results of the enzymatic hydrolysis of the woody biomass, it can be seen that, irrespective of the hydrolysed material (wood, cellulose, holocellulose), the material from the biomass stored in the open pile gave higher results. The hydrolysis efficiency also increased with time, independent of the type of material that was hydrolysed. The highest sugar yield from the enzymatic hydrolysis of wood was obtained for alder wood stored in an open pile. The highest sugar yield from the enzymatic hydrolysis of cellulose was obtained for cellulose extracted from alder wood—as well—that had been stored in an open pile.

Colour Change of Steamed Alder Wood Caused by UV Radiation

Alder wood (Alnus glutinosa L.) was steamed with a saturated steam-air mixture at a temperature of t = 95 °C, or saturated steam at t = 115 °C and t = 135 °C to obtain a pale brown colour, a light red-brown colour and a dark brown-grey colour. Subsequently, samples of unsteamed and steamed alder wood were irradiated with a UV lamp in a Xenotest Q-SUN Xe-3-HS after drying in order to test the colour stability of steamed alder wood. The colour change of the wood surface was evaluated by means of measured values on the coordinates of the colour space CIE L*a*b*. The results show that the surface of unsteamed alder wood as well as steamed alder wood with a steam-air mixture at t = 95 °C and saturated steam at t = 115 °C darkened and browned due to photochemical reactions caused by UV radiation. The opposite tendency was recorded at the surface of alder wood steamed with saturated steam with a temperature of t = 135 °C, where the deep dark-brown-grey colour lightened to a brown-reddish colour shade under the influence of UV radiation. The analysis of the changes in the coordinates of the colour space CIE L*a*b* shows that the greater the darkening and browning of the alder wood by steaming, the smaller the changes in the values of ΔL*, Δa*, Δb* of the steamed alder wood caused by UV radiation. The positive effect of steaming on UV resistance is evidenced by the decrease in the overall colour difference ΔE*. While the value of the total colour difference of unsteamed alder wood caused by UV radiation is ΔE* = 10.9, it decreased to ΔE* = 8.7 for alder wood steamed with steam-air mixture at t = 95 °C, which is a decrease of 20.2 %; for alder wood steamed at t = 115 °C it decreased to ΔE* = 6.5, which is a decrease of 40.3 %; and for alder wood steamed with saturated water steam with the temperature t = 135 °C it decreased to ΔE* = 5.7, which is a decrease of 47.7 %.

Gloss of Varnished MDF Panels Veneered with Sanded and Thermally Compressed Veneer

The objective of this study was to investigate the gloss of different types of commercially manufactured varnish systems, including water-based (WB), polyurethane (PUR) and UV-cured (UV), applied on veneered MDF panels with sanded and thermally densified alder and birch wood veneers. The varnishes were applied at various numbers of layers on veneered panels. The gloss was measured at three angles of incident light: 20°, 60° and 85°. Statistical analysis showed that the type of varnish, the number of layers, the pre-treatment process, the wood species and direction of wood fibers significantly affect gloss of the coatings of veneered MDF panels. The type of varnish had a dominant effect on gloss. The highest gloss values were measured for the UV-varnished surface, and the lowest for WB- and PUR-varnished surfaces. Gloss was enhanced with an increase in the number of layers. Birch veneer provided higher gloss values compared to alder veneer. The gloss values measured along the wood fibers were higher than those measured across the fibers. No significant differences were found between the coatings created on sanded and thermally densified veneers for the average gloss values measured along the fibers at angles 60° and 85°. This study could have practical applications for producing value-added furniture elements using low-value wood species pre-treated by thermal compression.