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Reconstruction and Restoration of some Zagreb’s Wooden Heritage buildings
2010 - IRG/WP 10-40498
In the last ten years, the huge amount of wooden buildings houses and objects of Zagreb’s cultural heritage were restored with fine workmanship. As the wood was one of the most used construction materials, the scientists and specialists from the Faculty of Forestry also took part in those restoration and reconstruction processes. The aim of this article is to inform and advice the restorers on the correct use of different wood species and the proper use of new and/or traditional preservatives and methods of preservation in the processes of the restoration and reconstruction.
R Despot, M Hasan

Biodeterioration of cultural monuments in the Republic of Macedonia
2008 - IRG/WP 08-10640
Research on the biodeterioration of the cultural heritage in the Republic of Macedonia was conducted from 2004 to 2006, one month per year. The expertise was focused on the biodeterioration caused by wood-inhabiting fungi and moulds. A total of 38 cultural monuments, including 37 monasteries and churches and one fortress, were inspected in the areas of the towns of Skopje, Ohrid, Demir Hisar, Debar, Strumica, Stip, Kicevo, Kriva Palanka, Kumanovo, Prilep, Struga, the region of the Lake Prespa, the Mariovo area and Kratovo. Most of the monasteries are under state protection. 15 of the inspected monuments had fungal damage. 32 macromycetes and micromycetes were identified on the constructive and decorative materials of the monuments. Wood-inhabiting fungi were found both on the indoor wood (bathroom, ceiling, stairs, roof inner portions) and external woodwork (gateway, bridge, outer door, roofs, stairs). Decay fungi dominated in the roof constructions of the inspected buildings. The majority of the identified Basidiomycetes in Macedonian cultural heritage sites belonged to white-rotters (81%), and the remaining 19% to brown-rotters. In several cases, mould contamination was noted on wall paintings, mainly Cladosporium sp., Aspergillus sp., and Fusarium sp. Fresh fungal damages found in monasteries and churches are dangerous for wood constructions and frescoes, and they must be eliminated.
I Irbe, M Karadelev, I Andersone, B Andersons

Mechanical strength of wood from the Vasa shipwreck
2008 - IRG/WP 08-20381
Samples from three ancient ship wrecks (Vasa, Elefanten, and Gröne Jägaren) and recent oak samples as reference were examined with regard to mechanical strength using the high-energy multiple impact (HEMI) - test method, which delivers the resistance to impact milling (RIM) of a material. Adoption and optimisation of the test method for the particular sample size of the wooden drilling cores was necessary. After that optimisation the HEMI method proved to be suitable not only for cube like specimen but also for specimens from wooden drilling cores. The RIM of the different wreck samples was partly significantly different from the recent reference material. Low values indicated deterioration of some cores. Interestingly the wooden core with high iron content showed the highest RIM, even significantly higher than that of untreated recent oak.
A O Rapp, C Brischke, C R Welzbacher, T Nilsson, C Björdal

The amazing wooden churches from Northern Romania - learning from the past, restoring for the future, preserving the present valuable heritage of forgotten wood building tradition
2009 - IRG/WP 09-10683
The beauty and the uniqueness of the north-western region of Romania called “Maramureş” are well known in Europe. Surrounded by mountains, the region remained to some extend isolated from modern influences, preserving the local village architecture and craftsman traditions learnt and passed on from generation to generation. Local folklore and past heritage sets you back centuries ago when the manual work and wood in particular was the only way to build. Wood construction with specific architecture has developed in this region. Houses and churches were erected in a way in which even today some of these building are still standing and integrate nicely with the landscape. As always good time and bad time are cycles in the human history and time have its impact on the any wooden construction. Restoring and preserving these unique wooden churches from Maramureş is not only a necessity for the local people but an honour and duty in order to preserve their heritage and traditions. In this study, a biological evaluation of the aged and destroyed wood from an historical wooden church from Maramureş, Romania, recently restored, is being investigated and discussed. The aged oak material used in the initial construction is compared with today’s oak wood material available on the market. The option of using VPT treated wood as a material of choice for restoring these monuments are being suggested and eventually considered as a recommendation. The knowledge, the talent and the traditional craftsman type of work used in building these churches are slowly disappearing and somehow needs to be preserved by maintaining this knowledge through restoration work. The question which remains to be answered is whether this material will last centuries like the original one used for construction?
R Craciun, R Möller

Effects of cold treatment on wood destroying fungi important in cultural heritage
2009 - IRG/WP 09-10706
The dry rot fungus Serpula lacrymans (Wulfen:Fr.) Schroeter is notorious in building environments for its vitality, destructive potential, and the huge costs associated with remediation of damage caused to wood of cultural heritage. Due to the potentially adverse of effects of chemical treatment methods such as have been attempted in the past, more benign physical methods of treatment, e.g. heat treatment, are currently under investigation. The diploma thesis of Marcus Lüdicke deals with the influence of cold treatment on growth of 5 brown rot fungi, 1 white rot fungus, 1 soft rot fungus and 1 blue stain fungus. Fungi were cultured with temperatures of 20°C, 15 °C, 10°C and 5 °C (Test series A). Test series B involved maintaining Petri dishes with mycelia of all fungi in refrigerators for one month at – 20°C or -80°C with subsequent recultivation on artificial media In test series C, Petri dishes with mycelia of all fungi were treated with nitrogen for 30 minutes at – 196°C. Results demonstrated that Serpula lacrymans is highly sensitive to cold treatment. No mycelial growth occurred from minus 20°C. Oligoporus placenta and Lentinus lepideus were very resistant to cold. Ophiostoma piliferum and Chaetomium globosum reacted with atypical mycelia growth. The potential applications of this new technique in cultural heritage will be discussed.
M Lüdicke, W Unger, G Binker

Qualitative - Quantitative Analysis of Wood-Inhabiting Fungi in External Wooden Structures of the Latvian Cultural Heritage
2010 - IRG/WP 10-10728
The frequency and diversity of wood inhabiting fungi in the exterior wood were established in the Araishi lake fortress, the Lielvarde wooden castle, the Latvian Ethnographic Open-Air Museum, Riga, and twelve wooden heritage objects in the Eastern part of Latvia (Latgale). The inspected wooden structures of the external woodwork included windows, stairs, walls, floorings, roofs, fences, and benches. Pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H.Karst.) were the primary construction materials used in the inspected objects. Roofs, walls and fences were the most commonly decayed outdoor structures. The fungi from the phyla Basidiomycota, Ascomycota and Protozoa (Myxomycota) were identified. Common fungal genera were Antrodia, Gloeophyllum, Athelia, Hyphoderma, Hyphodontia, Pharenochaete, Postia and Botryobasidium. Mainly corticoid and poroid species were recorded in the outdoor structures. The predominance of white-rot, represented by corticoids, in the external woodwork is explained by the location of objects in woody areas, where the source of infection and a favourable microclimate were ensured. The accelerating factors for severe wood biodeterioration in outdoor structures were (i) the presence of vegetation around the objects and (ii) the surrounding lake water, which ensured extra moisture for fungal development. The fungal diversity and frequency in the constructions were affected by the substrate (softwood/hardwood) and decay location (outdoors/indoors).
I Irbe, M Karadelev, B Andersons

Diagnosis of failures in wood beams from historical house in Banská Štiavnica – Relations between ultrasonic measurements and bending properties
2010 - IRG/WP 10-20437
Various degrees of rot and other damages in ceiling beams with dimensions of 6500-8800 x 160-200 x 240-310 mm (length x height x width) situated in one historical bourgeois house in the UNESCO town Banská Štiavnica, Slovakia were determined visually and by the PUNDIT-plus ultrasonic device. Subsequently, for seventeen of the most bio-damaged fir (Abies alba Mill.) beams chosen for exchange were carried out other ultrasonic tests and also “in vitro” ultrasonic and bending tests on small specimens (300x20x20 mm). “In situ” measurements have shown that the lowest velocity of ultrasonic waves is usually in the ends of beams, i.e. in their direct contact with walls it was only 300-400 m/s, while 0.5-1 m from their ends it was usually higher from 700 to 1100 m/s. “In vitro” measurements (the modulus of elasticity determined either by ultrasonic test – Ed, or by bending test – E; the bending strength “modulus of rupture” – fm) depended significantly on the density of tested fir specimens. High correlations were observed also between values of the dynamic and static modulus of elasticity, and between values of the modulus of elasticity and values of the bending strength. Achieved “in situ” and “in vitro” results could help at evaluation of bio-damages in other wooden heritage structures, as well.
L Reinprecht, M Pánek

Impact of climate change on wood deterioration - Challenges and solutions for cultural heritage
2010 - IRG/WP 10-20441
Deterioration of wood in cultural assets follows the same physiological mechanisms as in modern structures. Therefore rules and data for prediction of service life derived from old wooden structures can be used to model the service life of recent wooden structures and vice versa. The latter is done in this paper: From experimental test set ups in the field spread over Europe, climatic data, wood temperature, wood moisture content, and decay rates recorded for several years were correlated and used for mathematic modelling of decay. On that data basis a first attempt is made to quantify the influence of global warming on wood decay rates for different regions and scenarios, valid for both: wood in modern and historic structures. Against this background conservation of cultural heritage is increasingly challenging and methods are sought to allow historic structures to survive without severe modifications in design, but also with limited use of preservatives. How moisture monitoring can contribute to this purpose is shown on the example of the Echo pavilion in Maksimir Park, Zagreb, Croatia.
C Brischke, A O Rapp, M Hasan, R Despot

Wood Protection in Croatia – Situation from the Acquisition of Independence till Today
2010 - IRG/WP 10-40501
In the last eighteen years in Croatian wood-working industry, respectively wood protection industry, many good changes happened. In such a short period of time Croatian industry changed their “product philosophy”. After the fatherland war and acquisition of independence the most logs and sawn wood products have been exported from Croatia. With such “kind of philosophy” Croatian wood-working industry stopped in 2000 when Croatian Government decided to “force” producers (particularly small and medium sized saw mills and owners) to invest own money in kiln drying chambers. As the result of these economy measures, today Croatian firms mainly export semi-finished and finished wooden products. In spite of recession, which is everywhere recognised as the “bad thing”, at the top of the export list are parquet made from solid wood (or nowadays thermally modified wood), partly or completely kiln dried wooden elements for furniture and wood construction industry, solid wood furniture (cabinets, kitchen furniture), and smaller amount of joinery. The quality of those products mostly depends on the quality of protection and preservation. In the same time, knowledge on the wood protection and preservation arise, as among professionals and technicians in industry, as among scientist and researchers at the Forestry Faculty. The use of new technologies (such is modification methods) and new preservatives is greater than was twenty years ago. We hope that the new equipment in new wood preservation laboratories will encourage further research not only scientifically but even more for Croatian wood industry.
R Despot, M Hasan

Ecological methods and products for wood protection used for restoration and conservation of built heritage cultural assets to increase natural durability and duration of exposure in open air museums
2010 - IRG/WP 10-40506
Wood is a perishable material, hygroscopic and fuel, which cause attention to selecting the wood species that is going to be exhibited in relation to humidity and soil. With variable depending on its humidity and moisture from the atmosphere or soil, wood is a good living environment for fungi and insects, but suffer biodegradation processes and dimensional changes. Observations over time on wood building behavior determined limiting actions of biodegradation phenomena, with different products with antiseptic, waterproof and fireproof properties. The development of forestry research and of chemical industry in particular, have put on the market for wood protection treatment a number of solutions which subsequently proved toxic to humans and the environment. Now the latest generation methods and products available to conservators and restorers disposal for use in preserving the old wooden racks and the new one used in restoration. The National Institute Wood throughout over 75 years of existence, helped by laboratory and in situ tests, carried out by specialists, contributed to marketing the new products and ways to protect freshly shot down wood used in construction and in the conservation and restoration of cultural goods. Attempts are made by exposure to fungi, insects and moisture under laboratory conditions or by exposure to natural climate conditions in the polygon NIW. The preventive protection can extend about 3-5 times the duration of use and reduce downgrading quality with over 30% of the wood used.
M Pruna, D Purice, D Dumitru Copacean

The overview of ISPM 15 implementation in Croatian wood-working companies
2011 - IRG/WP 11-30576
Croatia is a small European county, but in the same time a great country according to it’s tradition in the forestry and wood working industry. However, around 48% of it’s territory is afforested. As the export is one of the main directions in the Croatian development conception, the production and distribution of wood package intended for the international trade, is one of the most important factors. By adoption of the rules of the phytosanitary requirements to be met by wood packaging material in international transport (NN 14/06), Republic of Croatia also incorporate rated standard ISPM 15 into their legislation. During last six-years of activities, phytosanitary system was established, and 84 companies are authorized to independently conduct heat treatment (HT) and to mark wooden packaging materials. Companies are well distributed throughout Croatia, which allows the Croatian economy unimpeded international trade of goods. During phytosanitary inspection, in the 67 authorized companies it has been found that those companies properly carry out the heat treatment (HT), while the main problems arise in the development of the Manual of authorized companies, traceable records, maintaining and certifying measuring equipment and marking of wooden packaging materials in international commerce. Observed deficiencies are mainly internal in character and have not caused adverse effects in international traffic, particularly in regard to the effects of internal pests (insects) HT sterilization.
R Despot, V Jambrekovic, M Hasan

The Significance of Natural Durability of Croatian Mediterranean Wood Species for their Traditional and Present Protection Methods and Use
2012 - IRG/WP 12-10770
The aim of this article is to contribute to the better cognition of the protection and use of some most important Croatian autochthonous Mediterranean wood species. Their traditional use and protection are observed by two aspects. The first one is the presence of these species in the Croatian Mediterranean regions for many centuries, and the long tradition of their use, regardless of their natural durability. The second aspect is the fact that most of the mentioned species have no particular technical and commercial value; respectively most of these species do not have sufficient natural durability and desirable permeability.
R Despot, M Hasan

Cultural heritage – research into innovative solutions and methods for historic wood conservation
2016 - IRG/WP 16-10874
Nowadays, interdisciplinary knowledge, tools and techniques are increasingly used to protect and conserve monuments representing our cultural heritage. This is of great importance especially in case of conservation and restoration of wooden historic artefacts which, as a result of physical, chemical and biological corrosion, have lost their technical, aesthetic and decorative properties. If those processes are not consciously stopped by appropriate conservation works, with the elapse of time they will start to threaten the existence of valuable relics leading to their irreversible destruction. Our generation is responsible for evolving modern, improved techniques and methods ensuring adequate, professional protection for historic artefacts. What is necessary to achieve this goal is close and smooth cooperation between conservators and museum workers, strongly supported by specialised knowledge of scientists representing diverse research disciplines, including biology, microbiology, chemistry, and physics. The aim of the new “Cultural heritage – research into innovative solutions and methods for historic wood conservation” project, supported by the Polish Ministry of Science and Higher Education ( “Dziedzictwo kulturowe – poszukiwanie nowoczesnych środków i metod konserwacji drewna zabytkowego”, No. 2bH 15 0037 83), is to develop new materials and techniques for conservation of wooden artefacts. Many different types of wood are planned to be studied, including dry wood (e.g. sculptures, paintings on wooden panels as well as various wooden constructions: churches, cottages, sheds, etc.) and wet wood (archaeological wood), individually selected for research in accordance to the level of wood degradation. The main idea behind the innovative solutions is based on technology using organosilicon compounds, particularly polysiloxanes and silsesquioxanes, and nanocellulose. Taking into consideration unique opportunities offered by the mentioned substances, it is highly probable that a new method for strength restoration of destroyed wood will be developed, which will therefore enable wooden historic objects to keep their shape and spatial form. Successful realisation of the project’s assumptions will open new horizons in research on conservation and preservation of wooden cultural heritage.
M Broda, B Mazela

Cryptotermes brevis - a silent earthquake for the wood structures in a World Heritage city in the Azores Islands
2016 - IRG/WP 16-50316
In the Azores archipelago the exotic drywood termite Cryptotermes brevis, detected in early 2000’s, is destroying the wood structures of the typical buildings and is already considered the main urban pest in these islands. This work aims to show the spread evolution of this pest along the last six years in the first Portuguese city classified as world heritage by UNESCO, Angra do Heroísmo. For six years, several buildings were monitored, using traps with glue to catch the alates (flying individuals), during the swarm season that occurs, normally, from the late spring until the end of summer. The number of captured individuals was used to determine the density per building. This data was analysed with a GIS in order to build risk maps of the termite spread in space along time. The results clearly indicate that the pest species is expanding. The city centre is no longer the only affected area. The percentage of buildings that are affected or in risk to be affected is very high in the entire city. Traditional construction, with timber load bearing structures, is being replaced by metal or other materials. There is still no Integrated Urban Pest Management implemented in the region or in the city. Therefore, with time, timber structures might become restricted to exist only in buildings like museums, churches or palaces.
O Guerreiro, P A V Borges, L Nunes

DuraSoft Project: a multidisciplinary approach for softwood protection
2021 - IRG/WP 21-50367
Over the course of millennia, fishing and agro-pastoral activities have produced unique housing types in the Italian lagoons and in the Slovenian highlands where the use of wood is predominant. They are associated with wooden service infrastructures such as piers, moorings, piling and fences. However, the existence of these structures and the associated cultural heritage are subject to constant maintenance no longer economically sustainable in humid and coastal environments where wood degradation is massive and fast. To overcome this problem, in the last century the use of particularly polluting wood protection products as well as of unsuitable materials have been perpetrated, causing environmental damage or unsustainable use of resources. The DuraSoft Project aims to test some new techniques and products, developed and produced by the partners, which intend to increase the durability of traditional wood species. The treated wood may be used for traditional constructions in socio-ecologically sensitive environments, making its use economically and environmentally sustainable within the Adriatic alpine-maritime area. The environmental compatibility of these techniques is evaluated through a broad spectrum of ecotoxicological tests. They will be applied at different levels of biological organisation, from the molecular and cellular responses measured in bioindicator organisms to the effects on epibionthic microbial communities. The wood species and the treatments applied are tested with different methods to evaluate both the wood materials and real objects degradation performances, applying also standard methods (EN 275, EN 252). Coniferous wood is historically used in the Alpine-maritime area of the Upper Adriatic, but is less durable than hardwood species. The objectives of the DuraSoft Project are particularly relevant due the high availability of softwood lumber following the recent disasters caused in the Alps by Climate Change.
I Guarneri, V Moschino, N Nesto, T Marceta, M Sigovini, E Borella di Torre, L Dametto, S Pasqual, M Humar, B Lesar, T Cibic, V Natali, E di Poi, F Cerino, D Formasaro, M Kralj, F Relitti, C Balestra, M Celussi, A Franzo, A Volpi Ghirardini, M Picone, G G Distefano, M Russo, D Marchetto, R Rakar, I Trobec, D Marinic, G Rep, N Thaler, T Galvan, R Lazzarini, F Gombac, D Tagliapietra

Danish wood preservatives approval system with special focus on assessment of the environmental risks associated with industrial wood preservatives
2001 - IRG/WP 01-50166-01
The following is a description of the procedure used by the Danish Environmental Protection Agency to assess the environmental risks associated with preservatives used in the pressure impregnation of wood. The risk assessment covers issues considered to be of significance for the environment and which are adequately documented so as to allow an assessment. Such issues are persistence and mobility in soils, bioaccumulation and the impact on aquatic and terrestrial organisms. Unless required in special circumstances, the assessment does not apply to birds and mammals as the normal use of preservative treated wood is not expected to involve any noteworthy exposure of these groups. Approval of wood preservatives will be based on a general assessment of the environmental risk associated with the normal use of wood treated with the preservative in a realistic worst case situation. The assessment may address other aspects such as disposal and total life cycle.
J Larsen

Data sheet on wood-boring insects. Apate monachus Fabricius. 2. Position systématique, nomenclature, identification et distribution - Espèces végétales attaquée
1981 - IRG/WP 1105
R L A Damoiseau

Confocal laser scanning microscopy of a novel decay in preservative treated radiata pine in wet acidic soils
1997 - IRG/WP 97-10215
Light microscopy of radiata pine (Pinus radiata D. Don) field test stakes (20x20x500mm3) exposed in wet acidic (pH 3-4) soil for 12 - 24 months showed predominance of an unusual type of decay characte-rised by tunnelling attack of wood cell walls. After two years decay was moderate to severe in wood treated to ground contact CCA specifications and also equivalent retentions of creosote, and a number of new generation preservatives. Relative to other New Zealand temperate test sites and also an Australian tropical site, the New Zealand acidic soil test site was very aggressive. Correlative scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were used to elucidate the micromorphology of this attack. Tunnels of diameter 0.2-5 µm were present throughout all layers of the cell wall, and their orientation was not related to cellulose microfibril orientation. They also showed no preference for particular cell wall layers, indicating a lignin degrading capability. CLSM images showed that living, connecting fungal hyphae were present in the cell lumina and tunnels. This type of attack was predominant in wood that was highly saturated with water whereas wood that was less moist was predominantly attacked by classical white rot. Ongoing isolation and incubation studies in conjunction with further microscopy should enable identification of the fungal species involved.
R N Wakeling, Ying Xiao, A P Singh

Effect of acetylation on decay resistance of wood against brown-rot, white-rot and soft-rot fungi
1989 - IRG/WP 3540
Effect of acetylation on decay resistance of wood was investigated using wood blocks of Cryptomeria japonica, Pinus densiflora, Albizia falcata and Fagus crenata. Blocks were treated with uncatalyzed acetic anhydride for different lengths of time and exposed to Tyromyces palustris, Serpula lacrymans, Coriolus versicolor and unsterilized soil. The action of OH-radical on acetylated wood was also examined using Fenton's reagent. The enhancement of decay resistance by acetylation was revealed clearly for all cases of exposures but varying with fungal and wood species used. For a brown-rot fungus Tyromyces palustris, the weight loss reached almost nil in all woods at 20 WPG (weight percent gain) of acetylation, after the striking decrease from 10 to 15 WPG. For a white-rot fungus Coriolus versicolor, it was counted until 12-15 WPG in the perishable hardwoods used, but not in a softwood Cryptomeria japonica, even at 6 WPG. In cases of another brown-rotter Serpula lacrymans and soil burial, effect of acetylation was intermediate between Tyromyces palustris and Coriolus versicolor. Anti-degradation mechanism by acetylation was discussed, from these weight loss - weight gain relationships, and the IR-and 13C-NMR spectral analyses of fungus-exposed wood.
M Takahashi, Y Imamura, M Tanahashi

The IRG..Chanelling information and ideas into the mainstream of wood preservation technology
1985 - IRG/WP 5241
IRG Secretariat

Wood preservation in Poland
2004 - IRG/WP 04-30362
Dynamic growth of market demand for wooden elements and articles, generated in Poland increase of interest in industrial preservation. Today, Poland is a substantial producer and exporter of wood made products. Majority of exported wood - approximately 70% - is scotch pine (Pinus silvestris L.), which, due to its natural durability, requires preservation.
A Kundzewicz

Wood preservatives: Field tests out of ground contact. Brief survey of principles and methodology
1976 - IRG/WP 269
This paper contains the following spots: 1.: The general need for field tests. 2.: Interests and limits of field tests in ground contact. 3.: Various methods in use for out-of-ground contact field tests. 4.: Fungal cellar tests are they an alternative to above-ground decay exposure tests? 5.: Conclusions.
M Fougerousse

The effect of certain wood extractives on the growth of marine micro-organisms
1977 - IRG/WP 438
S E J Furtado, E B G Jones, J D Bultman

Management of the wood and additives wastes in the wood processing industries: Problematics and technical answers review
1996 - IRG/WP 96-50073
Management pathways for pure wood subproducts are well known and used; but as soon as additives like preservatives, glues, varnishes or coatings are present within the wood wastes, their disposal or valorization becomes more tricky. The different kinds of mixed wood wastes of the wood processing industries, from the sawmill to the furniture manufacture, are identified herewith and their diversity is examined. These wastes can be classified according to their danger characteristics, taking into account the type of additives, their concentration, their availability for the environment, the physical state of the waste. Different disposal pathways are then considered. Combustion, with the possibility of energetic valorization seems the best answer for a major part of these wastes. But this is only possible if good combustion conditions are defined, so that no harmful products are emitted. Moreover, these conditions must be affordable on the technical and economical point of view. Then, some wastes cannot be burned in such a simple way, and need a larger approach, which is presented in this document.
S Mouras, G Labat, G Deroubaix

Biological screening assays of wood samples treated with creosote plus chemical additives exposed to Limnoria tripunctata
1980 - IRG/WP 408
Laboratory methods for exposure of treated wood coupons to Limnoria tripunctata are described. Chemical additions to creosote were screened using this method. Three pesticides, Endrin, Kepone, and Malathion proved particularly effective. The addition of varying percentages of naphthalene to creosote using several treatment methods are currently being assayed. Results to date show that the coupons treated by the empty cell method have better performance than those prepared by the toluene dilution method. The naphthalene coupons treated by the full cell method show no attack after six months' exposure.
B R Richards, D A Webb

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