**About the Editors**

**Anna Sandak** Research Group Leader of the Wood Modification group at InnoRenew Centre of Excellence and assistant professor and research associate at the Faculty of Mathematics, Natural Science and Information Technology at University of Primorska. She was previously employed at the Trees and Timber Institute of Italian National Research Council, where she coordinated the Laboratory of Surface Characterization. She has a PhD in Wood Science and an M.Sc. in Biology. Her research activities include the investigation of the multi-scale relationship and performance of modified and functionalized bio-based materials and implementing them as new architectural elements. Her passion is to search for biomimetic solutions for design of new materials and to promote knowledge-based use of bio-inspired materials in modern sustainable buildings. Her recent book "Bio-based building skin" was published by Springer Nature as part of their Environmental Footprints and Eco-design of Products and Processes book series.

**Jakub Sandak** A third-generation carpenter currently working as a researcher at InnoRenew Centre of Excellence and assistant professor and research associate at the Faculty of Mathematics, Natural Science and Information Technology at the University of Primorska. He was previously employed at the Trees and Timber Institute of the Italian National Research Council. He received his PhD in Agricultural Sciences from Tottori University (Japan), a Master of Science in Natural Resources Process Engineering from Shimane University (Japan), and is an engineer of Wood Science and Technology from University of Life Sciences in Poznan (Poland). His research interests include multi-sensor evaluation of wood properties, expert systems dedicated for wood machining process control and monitoring, organization of manufacturing processes in furniture industries, vision systems in the wood industry, characterization of the wood surface, physics of the wood cutting, wood mechanics and fracture, spectroscopy and chemometry, hyperspectral imaging, numerical modelling of wood at different scales, and mechatronics. His passion is designing, assembling, testing, and implementing prototype scientific instrumentation.

**Anna Sandak 1,2,\* and Jakub Sandak 1,3,\***


Wood has been recognized as an attractive alternative to several other traditional construction solutions, and it is often called the "building material of the 21st century". However, compared with other traditional materials, wood possesses some technical limitations and properties that, because they are less understood, remain difficult to control. The most problematic are low-dimensional stability, thermal steadiness, limited fire resistance, biotic and abiotic degradation resistance, and varying mechanical properties highly affected by the morphological structure of wood. These properties need to be improved to further enlarge wood application fields as well as reinforcing the confidence of architects, engineers, and consumers when using wood. New developments in the field of wood modification resulted in the discovery of highly innovative materials with enhanced properties for natural timber. Several of these reached the highest readiness level and are now mass-produced in high volumes. Further intensive research is in progress to discover new wood modification solutions to ensure improvement of wood properties and functionality, allowing elongated service life and reducing the risk of unexpected product failure. This Special Issue presents the newest research outcome in the field of the enhancement of native wood properties through a wide range of chemical, biological, and physical agents. It contains two reviews and ten research reports authored by researchers from four continents and 13 countries, namely, Australia, Finland, Greece, Iceland, Iran, New Zealand, Norway, Poland, Romania, Slovenia, Switzerland, the UK, and the USA.

An overview of functional treatments for modified wood is provided in a comprehensive review paper [1]. The manuscript presents two parallel but closely connected aspects of timber modification: the material functionalization strategies combined with the expected (multi)-functionality of timber products. The wide range of covered modification processes and the scope of applications proved that wood modification is not only the sole concern of a few wood scientists but it became a truly inter-disciplinary research area. Novel formulations, characterization methods, and serviceability are presented and deeply discussed in several publications contributing to the Special Issue [2–7]. A broad portfolio of characterization methods can be successfully implemented for the evaluation of complex mechanisms of deterioration process occurring during service life. Artificial [2,3], natural [4,5], and combined [6] weathering methods are used for the assessment of the performance of different substrates and coatings. The performance of wood finished with a broad range of coatings systems is highly improved when compared to that of unmodified wood. This confirms the great advantage of wood surface protection, especially when used in outdoor applications. Investigated coatings included transparent, semi-transparent, and opaque solutions based on different chemical compositions [3,4,6]. The performance of an innovative, bioinspired, and fully biobased coating system containing living fungal cells provides testimony for technological development. [5]. In this case, the desired occurrence of fungi as a part of the coating formulation provides self-healing properties. However,

**Citation:** Sandak, A.; Sandak, J. Special Issue "Wood Modification: Characterization, Modelling, and Applications". *Coatings* **2021**, *11*, 869. https://doi.org/10.3390/ coatings11070869

Received: 12 July 2021 Accepted: 16 July 2021 Published: 20 July 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

evidence of unwanted microbial cells is considered a major cause of the failure of timber products in use. Therefore, the fundamentals of fungal decay, staining, and mold growth processes, as well as analysis of the fungal attack mechanisms in the context of the state-ofthe-art knowledge, is reviewed [8]. Several suggestions for the future research directions in the new biocidal and non-biocidal coatings treatments are provided. These are essential for creating integrated coatings systems capable of limiting fungal attack while providing long-term protection against environmental factors.

A critical limitation of the natural weathering procedures is the fact that the test is very long-lasting. The novel methodology for the acceleration of the natural weathering test is presented [9]. It can be used for the generation of the weather dose–response models that are essential to estimate the future service life performance of timber elements. Machinability, mechanical properties, and other engineering aspects of the modified wood are addressed with consideration given to the specificity of arctic driftwood [10] as well as laminated wood composites [11]. The diverse positive effects of wood modification may be associated with the high environmental costs of the transformation processes. For this reason, a systematic comparison of the impacts associated with the most relevant modification technologies is presented in a dedicated review [12]. The impact of the expected service life extension, highly imparted by the proper use of modified wood in buildings, is simulated and profoundly discussed.

The broad spectrum of topics presented in this Special Issue provides a comprehensive update regarding ongoing research in this field. We do sincerely believe that such a compilation can be an inspiration for the further development of multifunctional and sustainable coatings, revolutionizing the wood sector of the future.

**Acknowledgments:** We would like to thank all the authors for their valuable contributions to this Special Issue, the reviewers for their reviews and useful comments allowing the improvement of the submitted papers, and the journal editors for their kind support throughout the production of this Special Issue.

**Conflicts of Interest:** The authors declare no conflict of interest.

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