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Drvna prašina tvrdih vrsta drva klasificirana je kao karcinogena tvar prema Direktivi (EU) 2017/2398 o zaštiti radnika od rizika zbog izloženosti karcinogenim ili mutagenim tvarima na radu. Termičkom modifikacijom drvu se mijenjaju mehanička svojstava i općenito smanjuje čvrstoća te se ono još više usitnjava pri obradi negoli netretirano tvrdo drvo. Cilj rada je određivanje učinkovitosti fotometrijske metode i dobivanje korekcijskog faktora za primjenu u određivanju masene koncentracije inhalabilne drvne prašine suhog tvrdog termički modificiranog drva. Termički modificirana jasenovina dobivena je postupkom sušenja na temperaturi od 90 °C do 126 °C, termičkom obradom u trajanju 20 sati na temperaturi 126 °C do 205 °C te postepenim hlađenjem tijekom 3 sata. Drveni obratci su obrađivanji kružnom pilom i rubnim profilerom. Optički uređaj Split 2 (SKC) na ulazu ima postavljen IOM držač filtra za sakupljaje inhalabilne frakcije i priključen je na Casella pumpu podešenu na protok zraka 2 L/min. Korekcijski faktor 1, 2 za fotometrijsko određivanje masene koncentracije prašine modificiranog tvrdog drva izračunat je omjerom masenih koncentracija dobivenih gravimetrijski i fotometrijski iz srednje vrijednosti 10 ponavljanja uzorkovanja. Pored istih radnih strojeva gravimetrijskom metodom dobivena je niska masena koncentracija inhalabilne prašine od 1, 273 mg/m3. Dosadašnja istraživanja pokazala su kako je bolja učinkovitost optičke metode pri nižim masenim koncentracijama inhalabilne frakcije i da je najbolja osjetljivost optike pri uzorkovanju čestica veličine 0, 6 µm pri ujednačenoj zaprašenosti. Poznato je da su najbolja slaganja rezultata gravimetrijske i fotometrijske metode za inhalabilnu frakciju (korekcijski faktor približno 1) dobivena za čestice veličine do 10 µm. Dosadašnjim istraživanjima korekcijskog faktora netretirane hrastovine i bukovine dobiveni su veći korekcijski faktori 2-3 za istu mehaničku obradu pa bi trebalo ispitati pretpostavku da obradom termički modificiranog tvrdog drva nastaje veći udio respirabilne frakcije u inhalabilnoj, što je uzrok boljoj učinkovitosti optičke metode. Učinkovitost fotometrijske metode uglavnom ovisi o sadržaju vode u drvu, vrsti drva i mehaničkoj obradi. Međutim, rezultati impliciraju na značajan utjecaj i veličine čestice koje prevladavaju u relativno niskoj koncentraciji. Općenito, fotometrijska metoda se preporučuje primjenjivati uz prethodno dobiveni korekijski faktor za specifične radne uvjete.

Lignin is one of the main macromolecular substances of the cell walls of wood, its part and chemical composition varies between species. Average percentage of lignin is between 20-40 %. There are several methods to quantify, in this paper the percentage of lignin in abonos (bog- wood) and oak wood (Quercus robur L.) was determined using three methods. Acetyl bromide method and Brauns lignin method which give values of the soluble part of lignin and Klason lignin method which also gives the part of lignin insoluble in acids. The soluble part of lignin for the three mentioned methods was determined by spectrophotometric analysis on a UV/Vis spectrophotometer at predetermined wavelengths, and the insoluble part was determined by filtration using glass fiber filter paper and its ignition. Obtained results of lignin percentages were calculated of absorption values obtained from spectrum and ash mass. Since all methods have certain changes in the structure of lignin, the values of lignin participation also differ, which is confirmed by the obtained results and preeceding research.

Conventional convective kiln drying is nowadays the most common way of drying wood in the Republic of Croatia, but it takes a relatively long time for the wood to dry. Therefore, wood processing companies have lately been investing in vacuum- press kilns. Those kilns allow them certain flexibility and speed to respond to customer requests, since the drying processes in them are usually much shorter. Since vacuum-press technology is a novelty in wood processing companies in the Republic of Croatia, in this paper vacuum-press drying process in one Croatian wood processing company was analysed from the point of occupational health and safety. The hazards which are present during the preparation and implementation of drying in vacuum-press kilns were detected and basic guidelines for safe operation in accordance with ISO 9001 standard are proposed.

Curved shapes of furniture parts are often used in furniture design and interior decoration. Production of curved shapes involves technology of wood bendingand it is manly done from bent veneer moldings and beechwood. For other types of wood, curved elements are made by sawing and joiningthe curved element from several smaller parts. Slavonian oak furniture belongs to high price class furniture. The aim of research is to explore the technological issues and possibilities for use of Slavonian oak in bendedfurniture elements. The frequency of use of curved shapes of chair elements, their dimensions, degree of curvature and constructional technological performance on existing products on the market will be investigated.The possibility of rationalizingthe described elements from technological, design and economic points of view will also be examined.

During some research wood often must be transported or temporarily stored and protected, while at the same time it is necessary to prevent the influence of solar radiation and water loss. For this purpose, most common protection used is transparent wrapping stretch foil. However, black wrapping stretch foil can also be found and bought on market in recent years. This black wrapping foil is opaque and at first glance it seems that it probably could be better for wrapping wood samples in it for protection. In this research oak wood (Quercus robur L.) small samples were wrapped in transparent and opaque wrapping stretch foil and exposed to various influences in the form of artificial UV radiation and Solar radiation. Thereafter, it has been determined whether there has been a change in colour.

Postupci obradbe drva ili drvnih poluproizvoda utjecajem topline i vode ili vodene pare.

Pojmovnik hrvatskog drvnotehnološkog nazivlja rezultat je rada na projektu Izgradnja hrvatskog drvnotehnološkog nazivlja (DRVNA), koji je financiran u okviru programa Izgradnja hrvatskoga strukovnog nazivlja (STRUNA-05- 2016). Pojmovnik sadrži 1445 preporučenih hrvatskih naziva iz područja drvne tehnologije i još 930 hrvatskih istoznačnica (dopušteni, nepreporučeni i zastarjeli nazivi te žargonizmi), a riječ je ujedno i o trojezičnom pojmovniku drvnotehnološkoga nazivlja jer su svi pojmovi popraćeni i s 1886 ekvivalenata na engleskome jeziku i 1770 na njemačkome jeziku.

Subfossil waterlogged oak-wood (Abonos) is very rare, expensive, and it is difficult to work with, with special emphasis on its drying. Additionally, information about correct procedures for moisture content estimation and monitoring of abonos is mostly scarce. In this research paper, investigation on how to conduct moisture content measurement and estimation correctly on subfossil waterlogged oak-wood from two different locations has been conducted, analyzed and discussed.

In newly built conventional wood drying kilns white deposits often occur on concrete construction parts during the process. These deposits occasionally cause confusion with investors for the reason they do not know whether deposits originate from wood or concrete. In this paper, inorganic origin of such deposits in a specific wood drying kiln has been affirmed. And additionally, efflorescence is discussed.

Determination and estimation of the moisture content in the wood is of the great importance for the proper and efficient conducting of wood production processes, and thus the achievement of desired quality of final products. Electric resistance type wood moisture meter is the most commonly used in production process for estimation of moisture content in wood, so it derived an idea to find a simple way for control of its accuracy and reliability. The precision of electrical resistance type wood moisture meter is measured by gravimetric method for the determination of moisture content. This simple method is designed, developed and tested at the Faculty of Forestry, University of Zagreb within the European IPA project Increasing competitiveness of Croatian industry of wood flooring on the EU market. The paper presents the method developed for control of accuracy of wood moisture meter, and the results of interlaboratory control of accuracy of electrical resistance wood moisture meters according to developed method.

U radu je sistematiziran pregled aktivnosti Sveučilišta u Zagrebu Šumarskog fakulteta u akad. god. 2014./2015. Obrađeni su svi segmenti rada Fakulteta s posebnim naglaskom na organizaciju fakulteta, znanstveno-nastavne i istraživačke aktivnosti, izdavačku djelatnost, međunarodnu suradnju, skupove te studentske aktivnosti. Brojne aktivnosti popraćene su ilustrativnim prikazima i tabličnim podacima.

Relevant properties of wood floorings are dimensional stability, hardness and strength, dependant on wood species, where also their workability, permeability and impregnability have the important role. Despite all the advantages, heat-treated timber has some undesirable properties comparing to the natural wood used for flooring, which depends also on the degree of thermal modification (Millitz 2002, Hill 2009, Straže et al. 2012). A lot of research on UV degradation of natural wood was done, using various surface coatings systems (Hägele 2003, Bulian et. al. 2009, Pervan 2011). There is less information about the behaviour of thermally treated wood in outdoor exposure under different weather conditions using adequate environmental- friendly surface protection.

Ručni uređaj, nomogram za određivanje vlage u zraku, i svojstava drva

Infrared (IR) thermography is a widely applicable non-destructive testing (NDT) method for measuring the temperature distribution of an observed object surface. Through thermographic analysis, the IR radiation intensity of the electromagnetic spectrum is detected and recorded on the obtained thermograms. IR thermography has its advantages and disadvantages but it is a promising technique, which is easily applicable in the field and has no harmful impacts on the operator or equipment. In wood science and related fields, IR thermography can be applied in production quality control, monitoring of manufacturing equipment and plants for hydrothermal wood processing, wood properties characterization, defects detection (particularly holes, rot and drying cracks), heat flux in wood, and more [1]. During the thermographic analysis, temperature is not measured directly, but indirectly. Therefore, many factors can affect the accuracy of temperature measurement during quantitative thermography analysis, and one such factor is the emissivity of the observed object. Emissivity of the material is the ability of the surface to emit radiant energy expressed as the ratio of the radiant energy emitted by a surface to that emitted by a blackbody at the same temperature and under the same conditions. Emissivity depends on wavelength, temperature, object surface (opacity, roughness, orientation), the material from which the object is made, angle of measurement. Although important, those associated parameters often are not entirely specified along with the emissivity value in the literature. Therefore the experiment for establishing thermo-modified oak wood emissivity values within spectral range 7.5 – 13 μm was conducted. Also the emissivity of innate oak wood was determined for the comparison. For the experiment, an FLIR infrared system with the following characteristics was used. Imaging and optical data were as follows : field of view 25° x 25°, minimum focus distance 0.1 m, focal length 10 mm, instantaneous field of view (spatial resolution) 2.42 mrad, F-number 1.5, NETD 100 mK, image frequency 9 Hz. Detector type: FPA, uncooled microbolometer, with spectral range 7.5–13 μm (LWIR, ISO–MIR), IRR 180 x 180 pixels. Oak wood (Quercus robur L.) specimens used in the experiment were radial texture elements clear of defects, with approximately the same three ring width. There were 60 innate oak wood specimens and 60 thermo-modified oak wood specimens with the final dimensions 270 mm (length) by 65 mm (width) by 25 mm (thickness). Innate oak wood elements were kiln dried and then four sides planed. The moisture content of the specimens was 9 %. Thermo- modified wood elements were kiln dried, then thermally treated and afterwards four sides planed. The moisture content of the specimens was 5 %. The moisture content of specimens was determined according to EN 13183-1:2002/AC:2003 Moisture content of a piece of sawn timber – Part 1: Determination by oven dry method. A polyvinyl chloride material with known emissivity in long wavelength infrared (LWIR) spectral range was applied to the surface of all specimens. The emissivity of the polyvinyl chloride material was verified and the oak wood specimens were heated to 50 °C. During the experiment, the ambient characteristics were as follows: air temperature 21 °C, relative humidity 60 %, reflected apparent temperature 20.2 °C, the distance of oak wood specimens surface from the lens was 120 mm, angle of measurement in relation to the object normal was 15°, airflow and dotted reflections were inhibited. Emissivity values were determined via FLIR software with an area box tool with following dimensions 70×30 pixels. There was a significant difference in the results for innate and thermo- modified oak wood emissivity values (two-sample t(df) = -15.6, p = 0.00).

The sorption- and chemical properties of ash- and beech wood after industrial heat treatment in water-vapour atmosphere were analysed by sorption thermodynamics, adsorbing surface fractality from sorption isotherms and by FT-NIR spectroscopy. Considerable reduction of water vapour sorption capacity after heat treatment of wood was confirmed at both wood species, more significant at beech wood in the middle hygroscopic range. Fractal dimension of internal adsorbing wood surfaces increased with amount of sorbed water and also after thermal processing. FT-NIR spectroscopy revealed most significant differences in chemical properties of hemicelluloses and revealed regions and bands, where considerable changes are appearing due to changed water sorption of innate- and heat-treated ash- and beech wood.

Furniture can be designed and produced for various purposes and this depends on how well it serves in use, and contributes to efficiency, effectiveness and satisfaction for final users. For furniture there are different standards that prescribe minimum requirements that a product must have. Those requirements are mainly related to the dimensions and technical quality. Even so, most users, designers, constructors and producers never perform evaluations of their furniture performance. The purpose of this paper is to discuss some factors and aspects important for evaluation of furniture usability. Analysis was performed on the example of 80 beds at the Croatian market. The results indicate that usability cannot be evaluated only by parameters defined and listed in standards. This proves the need for proposition to increase the number of factors, which define furniture usability.

This research paper reports on importance of botanical binominal nomenclature for wood trade and its influence on wood processing, especially on hydrothermal wood processing. Introduction to the basics of botanical binominal nomenclature is made in accordance with latest changes in International Code of Nomenclature for Algae, Fungi, and Plants (MELBOURNE CODE, 2012). The usefulness of knowledge about scientific names of wood species for manufacturers and end users is discussed. Some examples of wood drying defects that can occur due to lack of knowledge on specific wood specie scientific name are shown and elaborated. Also, a several wood species diversity comparison within the same genus related to the hydrothermal processing has been made.

Iz tiska je izašao Higrokalkulator, koji su izradili Prof. dr. sc. Stjepan Pervan i dipl. ing. Miljenko Klarić. Riječ je o grafičkom pomagalu koje služi za više različitih namjena u drvnoj tehnologiji.

This research paper reports on oven-dry oak wood (Quercus robur L.) emissivity value. Emissivity is very important property of material and it is used in infrared (IR) thermography. IR thermography is a non-destructive testing (NDT) method for measuring the temperature distribution of an observed object surface. It is applicable in a wide range of industrial and science applications. Currently in literature available emissivity values for wood differ from one another, and there is insufficient important complementary data. Often temperature, IR spectral waveband, wood specie, texture and other relevant wood information are not specified. Therefore the experiment for establishing oven-dry oak wood emissivity values within spectral range 7.5 – 13 μm (LWIR) was conducted, and the obtained results are presented in this research paper. Determined oak wood emissivity along with all important supporting data will facilitate the application of infrared thermography in wood related processes.

U rumunjskom gradu Iasiju, u Institutu za makromolekularnu kemiju “Petru Poni”, od 9. do 11. travnja 2013. održana je treća godišnja znanstvena konferencija COST Akcije FP 0904 pod naslovom Vrednovanje, prerada i predviđanje ponašanja termo-hidro- mehanički obrađenog drva primjenom eksperimentalnih i numeričkih metoda.

U sklopu 40. međunarodnog sajma namještaja, unutarnjeg uređenja i prateće industrije (16. - 20. listopada 2013.) Ambienta ´13, na Zagrebačkom velesajmu, u dvorani Brijuni, dana 18. listopada uspješno je održano 24. međunarodno znanstveno savjetovanje pod nazivom Drvo je prvo – materijal, tehnologija i projektiranje u funkciji korisnika. Organizatori savjetovanja bili su InnovaWood ; Šumarski fakultet Zagreb ; Oddelek za lesarstvo, Biotehniška fakulteta Univerze u Ljubljani, Zagrebački velesajam ; Hrvatsko šumarsko društvo ; Zveza lesarjev Slovenije ; Znanstveno vijeće za poljoprivredu i šumarstvo – HAZU, Akademija tehničkih znanosti Hrvatske ; Akademija šumarskih znanosti ; Hrvatska komora inženjera šumarstva i drvne tehnologije.

The FT-NIR spectroscopy showed high potential for predicting of tested physical properties of innate and heat-treated ashwood.

In this paper red thin line of thinking were conclusions determined from performed Croatian market analysis. These analyses showed that there are a lot of anthropometric measurements, material usage and green design, which are not in conformity with today furniture production criteria. Nowadays there are new stories of old traditions, and new thinking for the future. Many talented artists and designers rethink old concepts, and this is challenge for establishing base for framework for good living and its application. Designing is influenced by human factors and final human usage, where dimensions and a lot of other criteria judge final design. The changing role of design, a modelling of design problems leads us to empathic but in the same time multivariable feedback design, which emphasise one question: How good are good ideas? Design for the real world is in the same time aesthetic value and inherent part of final function, which is characteristic of good furniture. At the same moment anthropometric performance test of furniture design is the challenge for sustainable criteria development, what at the end will give us future evaluation of furniture design.

Recently, as a result of the recession there is decrease in demand for wood products on the Croatian market. As one of the methods for preserving wood industry production and increase competitiveness it is possible to introduce new commercially less interesting, rarely used species of wood in the manufacture of final products. These wood species are cheaper, which allows the final products of lower cost but with the same level of profit. One of these species is alder (Alnus spp.), which has great possibility in use, and its aesthetic characteristics can compete with commercially more used species. However, the presence of chemical substance named oregonin and difficulties in achieving of colour uniformity in hydrothermal treatment creates difficulties in further processing. The basic prerequisite for achieving high-quality wood is a good knowledge of the mechanisms of colour change, and this paper describes the oxidative discolouration of alder wood in hydrothermal processes with the aim of contributing to greater commercialization of this type of wood.

Heat treatment (HT) of wood is a promising technique for improvement of its dimensional stability, resistivity against biological and environmental factors as well as its durability. A heat treatment, besides positive impacts, also changes cellular structure of wood, its chemical characteristics, significantly reduces the wood density and most of mechanical properties [1, 2]. HT wood has a high potential for using it in outdoor applications, where can be exposed to continuously changing climatic conditions, causing heat transfer and moisture diffusion. The HT beechwood (Fagus sylvatica L.), used in the experiments, passed standard 1-day heating procedure at saturated steam conditions, consisted of pre-drying-, heating-, conditioning- and cooling phase. Clear, oriented wood specimens, (n = 7), 20 mm (width) by 100 mm (length), having various thicknesses (5, 10, 15 and 20 mm), were made afterwards from untreated- (C) and heat treated (HT) wood. Five side surfaces sealing of specimens using epoxy resin followed thereupon and conditioning at 20 °C and 40 °C having 33% relative humidity (RH). Diffusion experiments were made in adsorption, by exposing of specimens to 75% RH. The specimens were periodically weighted in short time interval, where the thickest material was also layered into 3 mm thick slices, for gravimetrical determination of moisture content (MC) profile. Diffusion coefficients were determined by traditional unsteady state method, using fractional change in average MC and a Newman equation for separating internal and external mass resistance [3]. Diffusivity was additionally analysed numerically by finite difference method, to asses the influence of moisture content. The heat treatment, according to the traditional unsteady state method, reduced moisture diffusion for 20% at low tested temperature (DC20 = 5.8×10- 11 m2 s-1 ; DHT20 = 4.7×10-11 m2 s-1). Mean moisture diffusion was for 2.6 times higher at 40 °C (DC40 = 1.56×10-10 m2 s-1 ; DHT40 = 1.25×10-10 m2 s-1). The diffusion ratio (DHT/DC ≈ 0.8) remained similar at both tested temperatures (Fig. 1). The finite difference method also confirmed the influence of heat treatment on moisture diffusion. It gave similar values of diffusion coefficients, for 25% higher at 20 °C (DC20 = 1.0×10-1o m2 s-1 ; DHT20 = 5.9×10-11 m2 s-1), and 10% lower at 40 °C (DC40 = 1.4×10-10 m2 s-1 ; DHT40 = 6.6×10-10 m2 s- 1), whereas variability of results was higher. The greater variation is ascribed to variability of wood properties, to uneven conditions during HT process, as well as to the achieved moisture content. The innate wood maintained higher MC at established climate conditions, and reached higher equilibrium moisture content (EMC) at initial and final state (Tab. 1). Additionally, increase of diffusion coefficient with the increase of moisture content was confirmed during adsorption process, more pronounced at innate beechwood specimens. Lower diffusivity of HT beechwood can be generally ascribed to lower hygroscopicity, most probable due to removal of hemicelluloses. In coincidence, the decrease of wood density presumably has positive, but less significant influence on moisture diffusivity of HT wood. We believe therefore, that physical changes of HT wood, like possible micro deformations of the cell wall structure, can not be neglected at mass transfer experimentations on this material.

Wood heat treatment (HT) is promising technique for improvement of dimensional stability and durability of wood, specifically needed for outdoor applications. Wood can be exposed in these cases to various loads and to continuously changing environmental and climatic conditions. Among many positive impacts the heat treatment also reduces the wood density and most of the mechanical properties, as well as changes rheological characteristics of wood (Gorišek and Straže, 2011). Characteristics of HT wood highly depend on the properties of the innate wood specie and used process parameters. Industrial heat treatment under steam atmosphere was performed on beechwood (Fagus sylvatica L.) with pre-drying, heating at 230 °C for 6 hours, followed by conditioning and cooling. Oriented micro-tensile wood specimens (n = 20), 1.5 mm (T) by 3.0 mm (R) by 50.0 mm (L), were made from innate- (C) and heat treated wood (HT). Firstly, short-term micro-tensile mechanical tests were carried out at half of the conditioned wood specimens in dry climate (T = 23 ± 0.1 °C ; RH = 33 ± 1%). Micro-tensile mechano-sorptive tests followed afterwards in specially designed apparatus (Navi et al., 2002), limited to the area of linear viscoelasticity (σ = 0.2×σmax) for 48 h, where climatic conditions were cyclically changed between relative humidities of 33 % and 75%, at temperature of 23 ± 0.1 °C. The mechano-sorptive test was combined of phase of free swelling and shrinkage (a), phase of transient moisture effect and loading on the mechanical response (b) and a phase of transient moisture effect on the strain recovery (c). Heat treatment significantly reduced density of beechwood in average for 21%, from 760 kg/m3 to 575 kg/m3. We confirmed also 15% decrease of modulus of elasticity (MOE) from 18.7 GPa to 15.7 GPa, and the loss of mean tensile strength, from 170 MPa (C) to 84 MPa (HT). The viscoelastic creep response of HT wood was slightly reduced, where the creep rate was decreased also (Fig. 1 ; Fig. 2) Differences were found out also at mechano-sorptive response between innate and HT beechwood, where the latter had almost no mechano sorptive deformation. The ratio of final mechano sorptive strain (εms) to initial elastic strain (ε0) reaches at HT beechwood less than half of the value of innate wood. The mechano-sorptive strain was the greatest in the first relative humidity cycle (Fig. 1 ; Fig. 2). Lower mechanical properties, less visco-elastic creep and mechano-sorptive deformations can be generally ascribed to chemical changes of HT wood, to reduced amount of water in the cell wall structure, to rearrangement of molecular structure as well as to less established and loosen bands between cellulosic microfibrils, hemicelluloses and matrix of lignin (Olsson et al., 2005). Micro deformations of the cell wall structure can not either be neglected.

Industrial heat treatment (HT) under steam atmosphere was performed on European beechwood (Fagus sylvatica L.), wherefrom small clear wood specimens (10 × 15 × 170 mm) were made and conditioned in standard climate. Transverse free- free vibration response and 4-point bending creep tests were carried afterwards to determine dynamic mechanical properties and creep deformation of the material. Heat treatment significantly reduced density of beechwood, equilibrium moisture content and stiffness at bending. Significantly greater and slightly faster bending creep response was confirmed at innate beechwood specimens. The heat treatment increased internal friction (tan ) of HT wood, determined by vibration response.

Thermally modified wood is increasingly used in outdoor conditions, but its surface also undergoes to degradation by weathering as well as unmodified wood. Oils are largely used for protection of wood surface in outdoor conditions because they are easy to maintain and recoat, and they enhance the appearance of wood surface. The change of colour and gloss and surface cracking of thermally modified and unmodified wood samples (oak (Quercus robur L.), ash (Fraxinus excelsior L.) and beech (Fagus silvatica L.).) were measured, treated with three types of oils during the accelerated weathering in QUV device. The use of oils reduced colour change of unmodified oak wood samples only in first hours of exposure (universal oil and teak oil up to 120 hours, and thermowood oil up to 180 hours) and for unmodified ash wood oils reduced colour changes during the most of the exposure with the exception of ash samples finished with universal oil. On unmodified beech wood samples universal oil reduced colour change up to 360 hours of exposure and teak oil and thermowood oil during entire exposure. It should be mention that teak oil and thermowood oil change the colour of unmodified wood to some degree because they contain pigments. Among three wood species of unmodified and finished samples ash wood samples showed the most prominent change of colour after QUV exposure. Colour change of thermally modified samples finished with teak oil and with thermowood oil was smaller during entire exposure than colour change of unmodified samples and samples treated with universal oil. The most prominent trend of colour change can be seen for thermally modified ash wood (at 190°C and 200°C) samples unfinished or finished with universal oil. Among unfinished thermally modified wood samples the smaller colour change could be seen for oak and beech wood samples. At the end of exposure the colour change of these samples was 1.7 smaller than colour change of ash wood samples. Oil treatment enhance gloss of wood surface and highest gloss values were measured on thermally modified beech wood surfaces, and the smallest were measured on ash wood surfaces thermally modified at 200°C. The gloss value of thermally modified oak wood surface finished with teak oil was 12 time higher than gloss of unfinished thermally modified oak wood ; the gloss value of thermally modified ash wood surface (at 190°C ) finished with same oil was 13 time higher than gloss of unfinished thermally modified ash wood, the gloss of thermally treated beech wood treated with teak oil was 19 time higher than gloss of unfinished samples and the gloss of value of thermally modified ash wood surface (at 200°C ) finished with same oil was 7 time higher than gloss of unfinished thermally modified ash wood. A rapid decrease can also be seen in gloss of thermally modified oil finished oak wood and ash wood samples during the first 26.5 hours of QUV exposure followed by small gloss changes with continued exposure. During the first 26. 5 hours of QUV exposure marked gloss change of thermally modified beech wood samples is also evident followed by more intensive decrease in gloss values compared to thermally modified oak and ash wood samples. The unfinished thermally modified samples showed only small changes in gloss during QUV exposure. The permeability of liquid water and water-vapour were also measured according to EN 927-5 and EN 927-4. Among all tested samples only thermally modified samples of oak and ash wood at 190°C, finished with thermowood oil and ash wood samples thermally modified at 200°C and finished with all three kinds of oils showed the value of liquid water permeability lower than 175 g/m2 which is according to EN 927-2 limit value for coatings intended to use for dimensionally stable wood products. Water-vapour absorption does not show such great deviations from values of unfinished wood surfaces which means that the treated surfaces do not prevent water-vapour absorption and liquid water uptake in the exposures to the high humidity for longer intervals (e.g. in autumn and winter months). All beech samples exhibited the highest values of water vapour absorption with the exception of unmodified samples treated with teak oil. Oils treatment reduced the cracking of the thermally modified samples. Teak oil and oil for thermally modified wood offered similar protection to exposed thermally modified wood surfaces from the effects of water and UV radiation, while the universal oil did not offer any protection from the colour change of modified wood during exposure. Since the oil coating is also susceptible to photochemical degradation, for a pleasant appearance of wood surfaces during outdoor use it is very important the timely refinishing in accordance with the manufacturer's instructions. It can be concluded that colour changes of thermally modified wood samples of all three wood species are reduced by teak oil and thermowood oil treatment during accelerated weathering. Gloss changes are the most pronounced at the beginning of the exposure, and later they are very small compared to the colour changes, for all wood species. All three species of thermally modified wood samples showed a lower permeability of liquid water than the unmodified wood samples. The lowest permeability of liquid water exhibited the samples treated with thermowood oil followed by teak oil, and the highest permeability exhibited universal oil for all three wood species. Tested oils do not prevent the absorption of large amount of water in the exposure to the high humidity for longer intervals. Untreated, unmodified samples of all three wood species cracked less than untreated thermally modified samples during accelerated weathering, and oil finishing of thermally modified samples decreased cracking. For a pleasant appearance of oiled surface during outdoor use the regular maintenance according to the manufacturer’s instructions is essential.

In the area of sitting furniture testing there are different standards existing that define minimal quality range. These kind of testing are long lasting and expensive. The intention is optimisation and shortening of testing time (and decrease of expenses) for standard chairs in production. Research object in this paper was standard joint consisting of round tenon and mortise. Also there were two modified tenon joints made. Joints were statically and dynamically tested. Results of static and dynamic testing are given in form of load momentum. High coefficient of correlation of all sample groups shows strong dependence between static and dynamic testing of samples. From results of three samples testing it can be concluded that there is possibility for decreasing expenses for quality determination especially those related to durability of construction (replacement of dynamic testing with static testing).