creative wood-based solutions

ISSN 0113-6224 Issue No. 28 December 2000

MGP8?

SAPSTAIN CONTROL

SELECTING KILN FILLETS Sawmilling Issue No. 28 December 2000

WORLDWIDE MARKET TRENDS IN RESIDENTIAL TIMBER FRAME CONSTRUCTION

Karen Bayne and Lisa Te Morenga

Timber frame construction is the predominant form dominant construction method in single-unit family of residential construction used in around 90 percent housing and in low-rise multi-residential units, of housing starts in New Zealand, Australia, USA, although recently, increased usage of alternative Canada and Scandinavia. systems has been seen. The light timber frame construction method is favoured because New Timber frame construction use is favoured in these Zealand builders are skilled and familiar with the countries because they each have significant material and the timber frame industry continues to softwood resources, it is the traditional construction advance. (eg kiln dried timber, pre-cut framing). method and there exists well-developed building expertise and codes and standards for timber frame construction. As a result of this expertise, timber The reasons for the great success of timber-frame framed houses in these countries are generally construction in New Zealand are:1 cheaper than alternatives, quicker to erect, thermally • Tradition: Maori built from wood and the earlier efficient and can have superior insulating qualities. settlers adopted these methods to quickly provide their families with shelter. Furthermore, there was Timber frame construction has an opportunity to a wide variety of high quality timbers available. expand into regions where there are presently We have developed a culture of timber construc- limitations, such as: tion. 1) timber resources are limited (India, Africa and to • Plantation Forestry: Our large radiata pine planta- some degree China) tion resource has substituted for rimu framing 2) there is a strong and long tradition of stone, brick from the post-war era, and the large availability of and masonry construction (Europe, the Mediter- high quality pine timber enabled the continuation ranean and Turkey) of traditional timber framing when the rimu 3) timber frame construction is perceived as inferior resource began to dwindle in the late 1960’s. to other systems, or as a low status building • Ease of construction: timber-frame construction is system (Parts of Asia, Central America, South quick and can be built in any weather conditions Africa) except rain. Once closed in and weather-tight, 4) building codes and standards discriminate against finishing can proceed rapidly. the use of timber (Republic of Korea, Japan, • Plant and tools for timber construction are moder- Spain and Mexico) ately cheap and simple. 5) termites are a problem (Southern USA, Hawaii, • High structural, thermal and acoustic performance Eastern Asia and Africa) can be achieved • Timber frame construction is adaptable. New Zealand Market For Timber Framing • New Zealand has a ready pool of expertise in design, construction and materials unequalled by According to Building Research Association New any other building system. Zealand light timber frame construction comprises • And our well-maintained timber framed homes 94.3% of single unit residential buildings, 45% of hold or appreciate their value over time, the multi-unit residential units, 39% of educational market is confident in the technology and financ- buildings and 50% of health sector buildings in New ing is readily available for both building and Zealand. Timber framing is likely to remain the buying second-hand.

Maria Langthaller 1996: Holzbau in Neuseeland, ein Vergleich zu Österreich. Diplomarbeit Technische Universität Wein Timber Frame Construction in the Rest of the legislation to give all workers every other Saturday World off work is expected to lead to growth in log cabin style resorts and holiday homes.4 In Korea deregula- The USA is the world’s major market for timber tion measures and restructuring programmes de- frame construction, where an estimated 1.5 million signed to stimulate housing demand favour growth timber framed homes were built in 1999, with most in single-unit family dwellings, for which timber is new housing starts in the Southern USA.2 In Canada the preferred construction material.5 and Australia new housing starts are only 10 percent of USA housing starts but these are also two of the Timber framing is now gaining popularity in West- world’s most significant timber framing markets. ern Europe because of its positive performance in Populations are small in Scandinavia and New environmental terms, especially compared to alter- Zealand, thus total housing start numbers are rela- native materials, and is booming in the United tively low but timber frame construction is the Kingdom, in particular Scotland and Ireland. In predominant style of building with 15-25,000 timber 1999, 53% of United Kingdom housing starts were frame homes constructed each year. timber framed, up from 33% in 1997.6 This has been driven, in part, by a very successful light-timber Growing Popularity frame construction drive in Scotland, and increasing concern over the environmental impacts of different Timber frame construction has slowly been making building materials. inroads into some non-traditional markets. Japan is the world’s second biggest market for timber fram- Although the construction market is not expected to ing, although other construction methods actually grow in Europe, significant remodelling and renova- predominate in this market. While the proportion of tion work is currently being undertaken, particularly timber frame houses in Japan is only around 10 in Germany and the Netherlands. There has been percent, the actual number of timber housing starts rapid growth in new construction in Eastern Europe, is still very high at more than 600,000 starts per but only a small amount is timber framed. Work in year.3 North American organisations are trying hard various Western European countries on multi-story to promote 2x4-style construction in Japan, although timber frame construction has also had positive most of the timber housing starts are of traditional results. Green consumers are likely to create growth post-and-beam type construction. in demand for timber frame construction over masonry, especially in Eastern Germany, the Nether- There is promising growth in the uptake of timber lands and France. frame construction in Korea and Taiwan. Like Japan, timber housing has a strong place in the China has a housing shortage and thus even a tiny cultural histories of these countries, but highrise increase in market share would constitute a large concrete structures dominate. In Taiwan, new opportunity for timber framed houses. However,

Table 1 - Total and timber framed housing starts for 1999 in selected world markets:

Country Total Housing Timber Framed Country Total Housing Timber Framed starts Housing Starts starts Housing Starts (estimated) (estimated) Australia 159,000 ~143,100 Netherlands 89,000 9000 Canada 150,000 ~124,000 Poland 67,000 2,000 China 21,070,000 89,000 Spain 320,000 500 France ~285,000 5,000 Sweden n.a. ~10,000 Germany 541,000 40,000 Taiwan 32,000 78 Ireland 19,000 n.a Thailand 20,000 n.a Italy 174,000 n.a UK 147,000 13,200 Japan 1,300,000 605,000 USA 1,663,000 ~1,497,000 Korea 300,000 1,000 New Zealand 26,000 24,500

2 World Wood Review 5 Craig Jenkins, Economist –“Korea Bounces Back” 3 JAWIC, Forest Research APEC Report 1999. 6 USDA GAIN Report: UK Forest Products Annual Report 2000, 4 USDA GAIN Report: Taiwan Forest Products Annual BRE Constructing the Future- Autumn issue, 1999. Situation 1999. 7 USDA GAIN Report: PRoC Forest Products Annual Report 1999. timber utilisation is low, and codes and regulations tion as there is a housing deficit of around 4.6 million do not favour timber frame construction. Currently, homes.8 Obviously it is an important market for the timber housing starts constitute around 93,000 out of USA, and there is some drive for USA styled construc- more than 9 million per year, but may soon reach tion there. In recent years there has been growth in comparable levels with Australia and Canada7 . timber framed construction, particularly in the north, where up to 24% of houses are timber framed, but Mexico has some potential for timber framed construc- overall, only 10% of houses are timber framed.9

There are many countries where we do not have rel- evant information about the position of timber frame construction. In particular Brazil and Russia are significant forest markets where there may be

opportunities. This map depicts the global opportu- nities for timber Market Opportunity for Timber Frame Construction frame construction.

EFFECT OF WOOD STRUCTURE VARIABILITY ON PROPERTIES

Adya Singh and Rolf Booker

Wood properties are determined by the chemical and secondary wall of a wood cell consists of three structural characteristics of its cell walls. To be able different layers that are commonly referred to as the to optimise process related conditions for producing S1, S2 and S3 layers. The main difference between high performance products it is important to under- these layers is the orientation of the microfibrils (the stand cell wall characteristics in as much detail as cellulose reinforcing strands). They may also vary in possible. While much is known about wood struc- the amount and distribution of the matrix materials. ture using conventional microscopy techniques, The three layers also differ from each other in their certain important features of wood cell walls require thickness, the central S2 layer being much thicker the use of more sophisticated high resolution than the others. Many precise measurements have microscopy systems. been made of the thickness of the S2 layer, but the success achieved in measuring the thickness of the The base material of wood cell walls is a uniform other secondary wall layers has been limited. This is matrix material that is chemically made up of lignin because the S1 and S3 layers are extremely thin and and hemicelluloses. This matrix material is rein- accurate thickness measurements require high forced with long cellulose strands called resolution microscopy, such as transmission electron microfibrils, just as fibre glass consists of a resin microscopy (TEM). matrix reinforced with glass strands. Just as a glass fibre fishing rod is made up of several layers of glass Recently at Forest Research we have accurately fibre to give it strength, a wood cell wall is also measured the thickness of the S3 layer in the made up of different layers to give it strength. The earlywood cells of radiata pine, some of which are

8 Housing Shortage in Mexico by Andy Salamone, Economist. 9 USDA GAIN Report: Mexico Solid Wood Products Annual Report Pt 2, 2000. shown in Figures 1 and 2. The thickness of the S3 withstand collapse, internal checking, and the attack layer proved to be highly variable in this wood of decay organisms. Thus it is very important to species. We recorded enormous differences in the extend this preliminary study to examine the thickness of this layer even among adjoining cells, variation in S3 layer thickness and composition. It is with a range of 0.06µm* to 0.3µm, as shown in particularly important to investigate this variability Figures 3 to 5. These results were unexpected, as it for the trees in our tree breeding programme that are has been assumed that the thickness of the S3 layer going to be the parents of the trees in our future in conifer wood is rather uniform. forests.

The difficulty in obtaining accurate measurements is probably one of the reasons why in the past the S3 layer has received much less attention than the much thicker S2 layer which forms the bulk of the cell wall in conifer wood. A second reason for believing that the S1 and S3 layers were unimportant was because these layers are much thinner than the S2 layer, which is reinforced by microfibrils that give stiffness to the wood. However, recognition is growing that although the S3 layer is very thin, it does have a vital role to play in the stability of wood in standing trees, the collapse of boards during drying, and in processes related to mechanical or chemical modification of cell walls. Examples of such processes are those involved in pulping and those aimed at property improvement of solid wood, such as compressing veneers and impregnating wood Figure 1 - Common walls between three adjoin- with preservative and other chemicals. In addition ing tracheid cells. The S3 layer of the three the S3 layer is likely to be an important factor in corner regions is similar in its thickness. The S3 biodegradation (wood decay) processes. Since layer in these regions is also considerably thicker chemicals used in the property improvement proc- than in the distant wall regions (arrowheads). esses and the microbial enzymes during biodegrada- TEM micrograph. ML, middle lamella; S1, S2, tion have to enter the wood cell wall through the S3 S3, secondary wall layers. Scale bar =1µm. layer, the thickness and the porosity of this layer will undoubtedly have an important role to play.

Not only is the S3 layer in radiata pine highly variable in thickness (as demonstrated), it is also known to be highly rich in lignin, its concentration reaching in excess of 50% in contrast to a lignin concentration of about 22% in the S2 layer. The high lignin concentration in cell walls has been related to greater resistance of wood to microbial degradation. The higher lignin concentration is also likely to reduce cell wall porosity, which would affect penetration of chemicals and enzymes during wood processing and biodegradation.

In conclusion, radiata pine shows enormous variability in the thickness of the S3 layer. This Figure 2 - Common walls between three adjoin- variability is likely to cause in turn major variability ing tracheid cells. The S3 layer in the corner in the accessibility of chemicals to the cell walls regions is variable in its thickness, being consid- during chemical penetration treatments for erably thicker in cell A than in cells B and C. hardening or preservation. In addition it will cause TEM micrograph. ML, middle lamella; S1, S2, huge variability in the ability of radiata pine to S3, secondary wall layers. Scale bar =1µm. * 1µm = one millionth of a metre (10-6m) Figures 3-5. A wide range in the thickness of the S3 layer is shown at a high magnification. The thickness of this layer in Figure 3 is 0.3µm, in Figure 4, 0.18µm, and in Figure 5, 0.06µm. TEM micrograph. Scale bar for all figures =250nm**.

DETECTING BRANCH STUBS ON LOGS

Louw Van wyk

A special table has been constructed to enable different technologies to be evaluated individually Forest Research to evaluate scanning technologies and in any combination. to detect trimmed branch stubs on logs The scanning table illustrated on this newsletter Traditionally log grading has been based on cover has been designed to enable sections of logs to dimensions such as diameter, length, taper, and be positioned on a scanning table and precision branch size. Additionally log form taking account of scanned to a resolution of 1 mm x 1 mm. A special sweep, ovality, eccentricity of pith have been used feature of the scanning table is a facility to enable and more recently stiffness based on density or the log sections to be removed and replaced in sound velocity has been included. Branching exactly the same position when a different scanning certainly effects the value of the sawn timber, and head is used. increasing the accuracy of branch information such as number of branch whorls, whorl spacing, branch Seven technologies have been selected for evalu- size can improve the sawpattern selection and thus ation on the basis of being able to be accomplished the value of the sawn output. with the available infrastructure. These are: 1. 3-D laser imaging. 2. Colour camera images. Previous work into log grade scanning identified the 3. Infra-red reflection/absorption. need for a more systematic approach to such 4. Laser tracheid scanner. scanning. This meant a system had to be designed 5. Microwave. where the same log section could be scanned using a 6. Stroboscopic effect. range of different sensing technologies, enabling the 7. Thermal imaging.

IS INTERNAL CHECKING HERITABLE?

Dave Cown, Rod Ball, Mike McConchie

A lot of research has been done on Internal problem to those striving to recover high-value Checking (IC) in the past few years, but it remains products from pine. Various theories have been an unpredictable feature of wood and a serious tested regarding site conditions and processing

** 2nm = 10-9 methods which might predispose lumber to this The results indicated that there is a possibility of a defect, but few hard facts have emerged except: high heritability for IC, but many more samples 1. Sapwood of young trees is more susceptible would be required for confirmation. The heritability 2. Mild drying schedules reduce the incidence estimate was quite high at 0.56, but the credible interval was 0.1 to 0.9. It was estimated that a sample size of 72 families (8 trees each) would give A recent study examined 13 year old trees from 18 an estimate with an interval of 0.3 to 0.7 and a families, growing in the central North Island. These standard error of about 0.1. were removed in a thinning operation, and 8 discs from each family (top of butt log) were subjected to Even if the heritability is confirmed to be high, it the “oven-drying method” to highlight the propen- will be many years before breeding alone can be sity to IC. The reason for using this material was to used to eliminate the phenomenon from lumber. In investigate the heritability of IC. The number of the meantime, research is continuing on several rings affected and the total number of checks were fronts to investigate the anatomical basis for IC, recorded for each disc. It was immediately obvious development of a non-destructive test, and trials to that all families at this site showed some degree of elucidate the impacts of silviculture and processing IC, and that, the incidence of checking did not meet methods. A national database will be established to normal statistical variability thus a heirarchical maintain records of IC incidence, and details of Baysian model was used to test for heritability. environmental and silvicultural factors.

MGP 8 - CAN IT BE SUBSTITUTED FOR NO 1 FRAMING GRADE IN NZS 3604?

Mike Collins, Doug Gaunt and John Roper

Forest Research is promoting the introduction to The code itself underwent a major face-lift with the New Zealand of another structural grade below introduction of many more diagrams and some MGP 10, the lowest Machine Graded Pine grade attractive design features to make the code more currently in use in Australia. Most timber structures accessible to users. are designed for stiffness. MGP 8 has a stiffness of 8 GPa - the same as that for No1 Framing visually In the production of the tables, however, the proper- graded. Thus the direct substitution of an MGP ties of visually graded No 1F radiata pine were still grade for a visual grade of equivalent stiffness, is a the basis of the calculations. There are differences simple way to introduce MGP grades to the New between the tables for No 1F radiata pine in earlier Zealand market. editions of NZS 3604 and the current code, simply because of the changes in engineering assumptions However, the strength properties of the proposed although the strength properties assigned to the MGP 8 grade are being reduced to better suit the timber were unaltered. faster-grown Radiata Pine logs now being supplied to our sawmills. Whether the reduced strength of For this exercise, the tables have been recalculated MGP 8 compared with visually graded No 1 Fram- using the strength properties for MGP 8 which is the ing grade presents problems for our Timber Framed MGP grade relating most closely to No 1F. The Buildings Code, NZS 3604, is discussed by Mike main factors leading to changes in tables in NZS Collins below. 3604:1999 recalculated for MGP 8 instead of No. 1 Framing are outlined below for each of the tables in NZS 3604:1999. NZS 3604 1999 – Changes to code and changes to tables For the following tables, no changes were necessary After a revision period lasting several years, a fully as strength is not critical, bending stiffness has not revised edition of NZS 3604 was published in 1999, changed nor has compression strength changed 21 years after the first launch. Opportunity was significantly. taken to adopt limit states design and the provisions Subfloor jack studs of the revised loadings code in a more rationally Bearers derived set of tables for most of the components. Stringers Floor joists Underpurlins and ridge beams Cantilevered floor joists Strutting beams Verandah beams Studs in loadbearing walls: These were completely Purlins or battens recalculated to take account of bending strength Ceiling battens property changes and code changes. There are no changes which are going to have significant eco- Tables for 3 kPa floor loads were recalculated as for nomic impact and those changes which have oc- tables in the main body of the code. curred are only by one size, sometimes up and sometimes down in size. Fastening properties The wood quality of MGP 8 is little different from Studs in non-loadbearing walls: These were com- No1F in the main, but as very low stiffness pieces pletely recalculated to take account of bending are excluded pieces with low density and poor strength property changes. Most of the changes fastening strength properties are also excluded from occur in the low wind area. Changes give both an MGP 8 timber. Hence fastener strengths will be increase and decrease in size. None of the changes more reliable. are of any significance.

Trimming studs: There were no changes in the tables Conclusion to the NZS 3604 design check. were needed as the sizes are derived from the sizes From the analysis above, it can be concluded that of normal studs. there are few areas in NZS 3604 where MGP will result in significantly different spans or spacings Lintel tables: These were completely recalculated to compared with our traditional No 1 Framing radiata take account of assumption changes and strength pine. Hence the good news; MGP 8 may be safely property changes. sold as a direct substitute for radiata pine visually graded No 1 Framing grade. Our studies to date Sill and head trimmers: No changes were necessary have shown significant financial advantages for the as strength is not critical and bending stiffness has adoption of performance grading of new crop not changed. Radiata Pine in the form of better MGP recoveries over the visual grading equivalents traditionally Top plates and Bottom plates: These were recalcu- used. Of course, the adoption of MGP grading lated as both bending strength and shear strength means that the sawmill must have a method of were changed and are critical in some cases. There stiffness grading (such as a Machine Stress Grader were no changes of any significance. or E-Grader as recently developed by Forest Re- search), and an appropriate Quality Assurance (QA) For the following roofing member tables, no changes programme to ensure the lumber being graded has were necessary as strength is not critical and bending the properties being claimed for it. Both Doug stiffness has not changed. Gaunt and Bruce Davy at Forest Research are Rafters available to help those sawmillers and manufacturers Ceiling joists wanting to set up performance grading operations Ceiling runners and appropriate QA schemes. Wood Preservation Issue No. 28 December 2000

MEMBRANE FILTRATION TECHNOLOGY HELPS TO TREAT NOVEL CCA TIMBER TREATMENT PROCESS KICKBACK

Hamish Pearson

INTRODUCTION restricted to a TOC concentration of less than about 110ppm. Based on these results, the objective of this The Multiple-Phase Pressure (MPP) process is a work was to test whether membrane filtration combined empty-cell timber treatment and fixation technology allowed TOC reduction in MPP kick- process using hot (≈ 75°C) chromated copper back down to less than 100 ppm, and to determine arsenate (CCA) solutions. During treatment almost the fate of any copper, chrome or arsenic ions which complete fixation is achieved during a 2-3 hour may be complexed with the wood sugars. treatment cycle. This differs from conventional timber treatment methods, where fixation occurs over a period of days or weeks. Additionally, the RESULTS timber is treated in one treatment vessel, requires no filleting, and is produced dry and therefore does not Five membrane types were trialed using MPP require a drip pad holding area to collect unfixed kickback including two reverse osmosis (RO) and treatment chemical drippage. Another advantage of three nano filtration (NF) membranes, as follows: the MPP process is that the working solution does Membrane Type 1:(model number ROAF) not sludge or lose its elemental balance, and thus Membrane Type 2:(model number NFDK) continual adjustment of working solution active Membrane Type 3:(model number NF45) ingredients is not necessary. Membrane Type 4:(model number ROBW) Membrane Type 5:(model number NFMPS) However, about 200 litres of kickback solution is produced per cubic meter of wood. The kickback Nano filters usually separate water and parts of salts solution contains up to 2500 ppm total organic (101 to 103 *10-10m particle size) whereas RO filtra- carbon (TOC), about 40 ppm copper ions, about 45 tion can separate water from parts of salts, sugars, ppm chromium ions and about 30 ppm arsenic ions. proteins and fats and bacteria (1 to 10 *10-10m Ideally the kickback solution would be returned as particle size). Each different type of membrane make-up to the main copper, chrome, arsenic (CCA) involved a different type of surface chemistry and working solution, but with such high organic carbon final filtration behaviour had to be found empiri- levels this is impracticable due to the occurrence of cally. sludging. If the wood sugars could be separated from the kickback solution, the water and trace copper, Membranes were operated at 10 and 25 bar pressure chrome and arsenic elements could be recycled back and 20°C. The membrane filtration area was 110 to the main working solution. Similarly if the TOC cm2 , and both feed (retentate) and permeate samples and CCA could be separated from the kickback were taken for later copper, chrome, arsenic and solution the remaining water could be used as make- TOC analysis. up solution, leaving a much more manageable volume of trace elements and TOC for later dis- Of the five membranes tested, the two RO mem- posal. In this way the MPP treatment process ap- brane types show suitability for reducing MPP proaches an environmentally friendly closed cycle kickback TOC down to levels below 100 ppm in the process. permeate. Results (Figure 1) showed the ROAF and ROBW filters can achieve 94 to 95% TOC reduction Earlier work has shown that no sludging occurs in down to between 72.35 and 92.54ppm TOC in the CCA working solution provided added kickback is permeate. CCA concentrations were reduced to 0.054 to 4.81 ppm for copper, 0.075 to 0.36 for temperatures and pressures to optimize kickback chrome and 0.11 to 1.16 for arsenic. treatment using either the ROAF or ROBW type membrane. An increase in membrane operating pressure from 10 to 25 bar decreased permeate concentrations of Overall the results are promising and show mem- CCA and TOC and increased the permeate flowrate brane filtration technology can improve the MPP for all membranes. Future MPP kickback pilot plant timber treatment process and be used effectively in factorial trials are already planned at different the wood processing industry.

Figure 1 - Copper, Chrome and Arsenic (CCA) and Total Organic Carbon (TOC) Permeate(P) and Feed(F) concentration levels as a function of membrane filtration type and pressure

10000 Cu (ppm) Cr(ppm) As(ppm) TOC (ppm)

1000

100

10

1

Concentration (ppm) 0.1

0.01 (F) (P) (P) (F) (P) (P) (F) (P) (P) (F) (P) (P) (F) (P) (P) ROAF ROAF ROAF NFDK NFDK NFDK NF45 NF45NF45 ROBW ROBW ROBW NFMPS NFMPS NFMPS 10bar 25bar 10bar 25bar 10bar25bar 10bar 25bar 10bar 25bar Cu (ppm) 33.625 0.054 0.054 31.875 1.3 1.9 30 9.915 4.00 29.875 4.81 1.86 28.67 0.73 1.01 Cr(ppm) 110.13 0.097 0.075 104.75 18.65 8.65 101.75 36.165 19.25 99.625 0.36 0.18 90.8 0.7 0.33 As(ppm) 20 1.3 1.13 36.25 1.0 3.0 27.5 0.5 0.6 13.75 0.11 1.16 20.0 1.3 1.3 TOC (ppm) 1437 92.54 84.64 1392 338.5 250.2 1344 383.5 243.9 1314 87.42 72.35 1323 177.3 136.3 Membrane filter type and filtration pressure

METAL CORROSION IN TIMBER TREATMENT PLANTS

Hamish Pearson

Forest Research currently operates a number of was built in stainless steel which gave the greatest large scale pilot timber treatment plants for research possible chance of fabrication success and a corro- purposes. One of these plants contains a unique sion test was set up to measure the performance of preservative labelled GP800, which is dissolved in different metals in situ. Successful metals could then methanol solvent. As part of an engineering evalua- be used for future plant possibly leading to a reduc- tion process, corrosion studies were undertaken tion in fabrication costs through the use of less using it to assess the suitability of different metal expensive metal or the reuse of existing site equip- components for plant fabrication. ment.

Although some information was found about the The six metal types evaluated for corrosion resist- corrosion performance of metals in contact with ance were stainless steel, mild steel, copper, brass, pure methanol, no data was found in the literature aluminium and galvanised steel. Ten, 2-3mm thick about the performance of difference fabrication samples of each metal type were machined to metals when placed in contact with the unique 150mm by 40mm and one hole drilled in each for preservative GP800. Because of this, the pilot plant fastening to the test rack. The rack was made out of non conductive Acetyl plastic with each 0.45 sample placed 40mm apart from its 0.40 0.39 nearest neighbor so as to eliminate any galvanic cell type interaction. Samples 0.35 were cleaned ultrasonically and weighed and measured for volume and density 0.30 0.29 before treatment. Then, after 644 days in- situ each sample was brushed, ultrasoni- 0.25 0.20 cally and cathodically cleaned before 0.20 final weighing. The corrosion rate, in mm/yr, was calculated using the standard 0.15 method detailed in ASTM G1(90). mean corrosion rate (mm/yr) 0.10 0.06 Corrosion rate results are outlined in the 0.05 0.04 0.00 figure opposite. Results showed stainless 0.00 steel, with a calculated corrosion rate of stainless mild copper brass aluminium galvanised zero mm/yr, is the best choice for pilot steel steel Metal Type plant construction metal when using GP800. Similarly copper and brass corroded very little with mean rates of 0.06 and 0.04 mm/yr respectively. How- ever, aluminium, mild steel and galvanized iron did played severe pitting whilst galvanized iron suffered not perform well and corroded at 0.20, 0.39 and 0.29 from surface build-up of a white compound which mm/yr respectively. Aluminium additionally dis- was probably zinc oxide.

IT’S THAT TIME OF YEAR AGAIN!

Robin Wakeling

Sapstain control can be a much bigger problem in Theoretical Sapstain development after 12 weeks the summer! Conditions Penetration Rate Sapstained Wood (°C) (mm/day) (%) The warmer months are just around the corner. Loss of value of logs and lumber caused by sapstain, Longt. Rad Tang mould and decay fungi usually occurs during the Optimal 10 3 1.0 3.00 summer months. Greater awareness of issues that Sub-Optimal 3 1 0.5 0.15 lead to problems and a few extra checks can prevent such problems from arising. A recap of some of the key principles of sapstain The following table makes the point regarding the control greatly accelerated rate of sapstain development during optimal summer temperatures. The rates of In-service methods of controlling sapstain penetration of sapstain fungi into wood have been The sapwood of all timber species is susceptible to demonstrated in the laboratory at temperatures close fungal degradation, albeit to varying degrees. There to those that are optimal for fungal growth (22 – are only two proven, in-service, methods of prevent- 28°C) and in conditions that are closer to winter ing fungal degradation of freshly felled timber temperatures (6 – 12°C). The table shows that an indefinitely: approximate 3-fold increase in penetration rates 1. Dry the wood to a moisture content of below during summer temperatures equates to a 20-fold 18% of its dry weight; increase in the volume of wood occupied by 2. Keep wood in a saturated condition by ponding sapstain. This calculation was based on sapstain or sprinkling with water, thereby maintaining an development in a log of a 35 cm diameter. inhibitory (low) oxygen concentration. When these methods are not feasible, wood is should be exercised when receiving advice that protected by applying a prophylactic treatment, suggests one type of antisapstain treatment is suit- commonly called an antisapstain treatment, to the able for all situations. Data demonstrating the surface. An antisapstain chemical is obtained in a efficacy of the new product under operational concentrated form (usually a liquid) consisting of a conditions similar to those of the prospective user, fungicide plus appropriate solvents and surfactants should be asked for and checked. to disperse or solubilise the fungicide upon dilution with water. The diluted treatment, or working solution, is then applied either by dipping or spray- Why is control of sapstain in logs more difficult than ing. in sawn timber? The underlying difficulty resides in delivering a The number and complexity of factors that can fungicide layer or “envelope” evenly to every part of affect degradation of sawn timber and logs is great, the log surface, and then keeping it intact during but the science of prevention is straightforward, and handling. Logs are covered with pits, gashes and reliable protection can be achieved for 4 – 6 months scuffs of all shapes and sizes, and it is inherently for sawn timber and 3 – 4 months for logs. difficult to treat these areas. Having received an antisapstain treatment, sawn timber is handled with “kid gloves” compared to logs. The great majority of The limitations of antisapstain treatments the wood surface of sawn timber, within a stack, is If an appropriate dose of antisapstain chemical is not submitted to any kind of damage, that could applied evenly to every surface of freshly felled and breach the fungicide layer. In sharp contrast, a log sawn radiata pine, wood degrading fungi can be surface is heavily abraded by machinery, other logs controlled for 3 - 6 months in New Zealand. The and any storage surface onto which logs are length of protection depends largely on the prevail- dropped. Sawn timber is less prone to other surface ing climatic conditions (predominantly temperature), fungicide depletion mechanisms, such as greater which are usually a function of season, and on exposure to rainfall, and contact with dirty storage whether the timber is stored as a filleted or block- surfaces. stacked packet. Other factors may in some instances be significant, including fungal species, tree age, Another possibility for fungicide depletion on logs is season at time of felling, forest location and inherent related to the more severe drying stresses that occur properties of sapwood such as nutrient and extrac- at the surface. As an uneven wood surface dries, tive content. In other countries the length of protec- movement between abraded wood fibres will occur, tion achieved may be different, and this is largely possibly breaching the fungicide layer.This is dependent on the climate and timber species. particularly the case for adhering bark residue which tends to curl back away from the underlying un- treated sapwood. The slimy cambium residue left Whilst increasing the dose and inherent potency of behind in those areas of a log surface where the an antisapstain chemical can extend the length of debarker has not made contact with the sapwood, protection achieved, there are defined limits. may also be a difficult surface to coat with fungi- Antisapstain chemicals applied to the surface of wet cide. The cambium is very turgid with water and wood will remain at concentrations that are toxic to shrinks dramatically upon drying, exacerbating fungi for a finite period. There are many mecha- surface movement and possible breac0hing of the nisms of fungicide depletion and this topic is beyond fungicide layer. the scope of this article. The key point is, obtain accurate information of the longevity of the antisapstain treatment being used from the supplier. Good housekeeping guidelines for avoiding Choice of the most cost-effective antisapstain sapstain problems this summer treatment is dependant on many factors, many of which are specific to local climate, geography, 1. In the summer, unless sawn timber is to be kiln handling and transportation conditions. The best dried immediately, sawlogs older than 10 days approach to appropriate selection of an antisapstain from the felling date (do not rely on skid site formulation is consultation with a reputable supplier date), should be rejected by sawmills. If sawn who is able to explain the merits and limitations of timber is to be kiln dried immediately, older logs, the various products within their range. Caution up to 1 month from the felling date, can be sawn, provided low levels of sapstain (up to 10% cover 3. If in doubt ask your antisapstain product supplier of boards) are acceptable. or Forest Research, for information on good 2. In the summer, logs for export should be de- housekeeping practices. The information in this barked and antisapstain-treated within 3 days article is given as a guideline. Sapstain is a from the felling date. Very few antisapstain biological phenomena and is therefore unpredict- treatments are effective for protecting logs. able, and whilst guidelines are useful much of the Check with your supplier of antisapstain products time, there will always be exceptions. that they have a recent track record for protecting export logs (ask for mill trial data that were Don’t chance to luck, do the checks, but since luck derived from full scale logging operations, as is never a bad a thing to have, we wish you plenty of there is no substitute). it this summer! Wood Drying Issue No. 28 December 2000

SELECTION OF KILN FILLETS

Steve Riley and Tony Haslett

One question we are often asked is: “What sort of dom width boards). At the end of this article we fillets should I use, what size should they be and have provided the names of two companies how long should fillets last?”. importing hardwood fillets. One of these hard- wood fillet suppliers contends that in the USA In the overall picture of drying it is all too easy to their fillets have a life expectancy of over 100 forget about the cost of fillets but, at 40-70 cents cycles, and that they are successfully used in HT each they can become a significant contributor to the drying at up to 140°C. cost of kiln drying. We have only once investigated • Plywood and LVL: Both of these materials are the life expectancy of fillets. In 1972 when we did reported to give a substantially longer life than the investigation, the maximum drying temperature solid pine fillets. However, with rough machine was only 75°C, so this may account for the fact that filleting these fillets tend to delaminate at the ends the loss of fillets was only 50% per annum. Now and develop a paint brush-like appearance. When with ACT and HT drying and final steaming, which the glue lines are on the 40 mm wide face these accelerate the thermal degradation and makes the fillets are stiff and have a long life, but where the fillets brittle, many companies report that their pine glue lines are on the side there is a tendency for fillets are lasting less than 10 charges (with no hard sagging where the fillets are unsupported. data to support this). • Plastic: There are several companies interested in providing plastic or phenolic resin stickers but the severity of New Zealand drying conditions has Fillet Materials to date prevented their successful introduction. In choosing the fillet material, a balance must be • Aluminum and Tubular Steel: In his book struck between low initial cost (low material qual- “Softwood Drying”, Larry Culpepper writes that ity) and a likely short life expectancy, and more aluminum fillets have a tendency to bend rather expensive but more durable materials. In addition to than flex under load, and that once bent their life material properties, the life of fillets will also be expectancy is short. From a work safety aspect influenced by the stacking system, sawing accuracy, they can be too hot to touch if they are not al- gaps between boards and stack handling systems. An lowed to cool between loads, and over time they enormous range of materials can be used for fillets are reported to develop sharp burrs. including: • Softwoods: The most common fillets used in New Zealand are pine and Douglas fir. To obtain Thus on balance it seems likely that most companies acceptable life from fillets of these species, the will stay with dry gauged softwood fillets, but raw material should be free of knots and have hardwood fillets might offer an attractive option (see minimal cross grain. Material should be kiln dried later section). to at least 10% moisture content and then multi- ripped and gauged to thickness. • Hardwoods: As with softwood, it is preferable Fillet Shape for material to be kiln dried prior to multi-ripping Several New Zealand companies have used a and gauging. The high density, and high strength rounded bull nose profile on the edge of the fillet. and stiffness of hardwoods makes them very The bull nose looks smart and in manual filleting it suitable for fillets. Hardwood fillets are less likely can reduce splintering, but in machine stacking it to break and/or bend when unsupported (in prevents fillets sitting on their edges. However, situations such as across the gaps between ran- moulding in a bull nose profile increases fillet production costs, and the removal of wood fibre The resultant drying cost curves ($/m3)* were weakens the fillets. similar for most options and are typified below.

The use of rebated fillets (with a mid-width rebate of about 10-mm wide by 5 mm deep) was assessed by Forest Research as a means of reducing stain under

the fillets, particularly for rimu. We could find no 3

evidence that rebates reduce rimu fillet stain, and see $/m no benefit from using rebated fillets for drying radiata pine, and the indent left by hardwood rebated fillets can be unsightly.

0 5 10 15 20 25 30 Fillet Width fillet thickness mm * A $m3 scale has not been shown because this will vary slightly Traditionally, New Zealand sawmills have used 40 with fillet cost and life mm, and on balance this is the width we recom- mend. Differential drying under the fillets may cause Figure 1 - Effect of fillet thickness on drying cost checking, particularly in the HT drying of boards over 150-mm width. Studies show that if this type of checking occurs it is advisable to reduce fillet width The work showed that because stack airflow resist- to 30 mm. However, reducing fillet width will also ance rises dramatically with thin fillets, there is an reduce fillet strength, and therefore life, and cause increase in electricity consumption. When the problems of fillet indentation. Wood of radiata pine effects of fillet thickness on electricity consumption has only moderate density, and the stack weight and lumber volume are considered, the following from high stacks plus the top restraining weights can general implications were evident: cause fillet indentation in the lumber if the fillets are • There is a minimum drying cost at about 15 mm too narrow. fillet thickness, meaning the optimum fillet size is about 15 mm. • For fillets thicker than this optimum, the reduced Fillet Thickness volume of lumber per charge slowly begins to We are often asked about changing the thickness of dominate, giving slowly increasing drying cost. fillets from the commonly used 19-mm thickness. • Below this optimum, the drying costs start in- Some people wish to increase the thickness, allow- creasing dramatically due to increased electricity ing more airflow thus hopefully speeding up drying. consumption, which rises due to the increased Others wish to decrease the thickness, ensuring more stack air resistance. throughput because of the increased charge volume. However, the selection of the appropriate fillet thickness is a complex question depending on When we did this work we thought that the slight individual kiln design and cost, the relative costs of reduction in drying cost associated with the use of electricity and heat, and the cost and life cycle of the 15mm fillets would be more than offset by the costs fillets used. associated with additional fillet breakage. Thus we concluded that if pine fillets were used then 19mm thickness was probably more appropriate than 15 Investigations were carried out on optimizing fillet mm. However, the recent availability of strong and thickness by Forest Research in the early 1980s. durable hardwood fillets raises the issue of whether The work assumed that equivalent air volumes gave it would be beneficial to change to 15mm thick equivalent drying times, and that the kilns were hardwood fillets. designed to deliver the given flow being used. Overall drying costs per m3, which is the sum of A word of caution. The theoretical work on fillet electricity costs for the fans, heating cost and cost of thickness and drying cost could be easily improved capital, were calculated for fillet sizes ranging from with modern tools such as the Forest Research full 7-30mm. Fillet costs and life were ignored, and a stack drying model, and the modelling then needs to wide range of energy costs and kiln capital costs be backed up with some work on fillet life in rela- were examined. tion to fillet size. Suppliers of Imported Hardwood Kiln Fillets: George Olsen McCorry and Co Limited Kevin Lewis Heritage Plaza, A 10-3 KLC Limited Jalan Lintas, Luyang PO Box 5003, P O Box 15148 Rotorua West 88861 Kota Kinabalu Phone 07 349 2862 SABAH Mobile 025 2777201 Phone +60 88 726681 Mobile +60 19 853 0544 Fax 07 349 2074 Fax +60 88 726690

FIBREGLASS PANEL INNOVATION FOR WOOD DRYING KILNS

Tony Haslett

A lightweight insulated panel that could be the Polyurethane foam is used in premium high-effi- answer to many a design dilemma is being manufac- ciency refrigerators and freezers as it has twice the tured by pultrusion specialist Gracol Enterprises insulation value of standard polystyrene. Ltd. of Christchurch, New Zealand. Made from pultruded fibreglass, the product is a self-supporting structural panel that can withstand corrosive envi- The 50-mm thick, the panels are highly rigid due to ronments, high humidity and extreme temperatures. internal fibreglass members that provide the web strength for the tough fibreglass skin. The 600-mm wide panels also have an innovative weather-tight Pultrusion is the automated mechanical process of locking edge that allows side-by-side joining of making fibreglass reinforced plastics (FRP) of a panels to create a large lightweight surface on which constant profile. Using a heavyweight person the latest resin tech- can safely walk. nology and incorporat- ing twice as much glass fibres as the Design engineers in traditional hand-lay Dunedin have used the method. It has high panel for both fixed strength and is has low and easy opening susceptibility to covers in large diam- thermal expansion eter sewerage tanks. Development is also underway to utilise the Although fibreglass is product for portable, a superior insulator in modular, easy-to- its own right, “high assemble, insulated tech polyurethane houses for Antarctica foam is the meat in the researchers. fibreglass sandwich” which makes this panel a top performing Gracol has developed thermal barrier, hot or other useful products cold. This poly- for the kiln drying urethane foam can industry. Their long- withstand tempera- life fibreglass spacers tures as high as 180 for use in kilns have degrees Celsius (375 generated interest. degrees Fahrenheit). MODELLING OF SOLVENT DRYING FROM TREATED WOOD PRODUCTS

Hamish Pearson

Estimating solvent concentrations retained in can be separated into component parts using treated wood can be a problem! Raoult’s and Dalton’s laws assuming ideal behav- iour and relatively mild molecular interactions Much is known about water and wood relationships between water, the organic solvent and wood. with respect to moisture changes. However, when another volatile liquid compound is added, as with Relative volatility and gas concentrations are easily wood and wood products treated with a preservative calculated from standard equations using mole compound dissolved in a volatile organic compound, fractions and partial pressures. The use of several the situation becomes more complex due to the Microsoft Excel spreadsheets along with Microsoft presence of a binary solvent mixture. Each volatile Visual Basic Macros programs, embedded in the liquid will dry at different rates from wood depend- spreadsheets, can be used effectively for calculation ing on their respective relative volatilities, boiling iterations. points, temperatures, initial concentrations and whether or not Raoult’s and Dalton’s laws are Theoretically a drying curve could be estimated obeyed. Detection and estimation of solvent com- entirely from relative volatility equations by know- pounds in wood is important from economic and ing the initial wood concentration of water and health and safety points of view. Solvent concentra- organic solvent. However, by using an empirically tions may need to be reduced to acceptable levels, obtained drying curve more accurate piecewise whilst solvent recovery during some stages of drying calculations can be made between data points which can lead to solvent recycling and reuse. closely reflect the real situation. Figure 1 shows a typical empirical drying curve, which has subse- A method has been developed which models solvent quently been separated into the water and volatile loss from wood for different drying conditions. The organic compound components and assumes the method allows solvent concentration levels and organic solvent is more volatile than water. drying rates to be estimated, for a binary system, without costly gas and solvent detection apparatus 600 and leads to further drying rate predictions for a variety of kiln conditions which is important for 500 estimating kiln schedules when drying solvent Total organic solvent & water water treated wood. 400 organic solvent

Developing the model 300 Mass (g) For a liquid pool comprised of two volatile solvents 200 both compounds will evaporate at a rate relative to their initial concentrations and their relative volatilities, provided Dalton’s and Raoult’s laws 100 hold. If the situation is extended to wood the liquid 0 pool can be thought of as being contained in the 0 5 10 15 20 25 30 35 40 45 50 wood, but is free to evaporate in much the same Time (hours) way as evaporation occurs from a liquid pool in an open container. For wood products treated with a Figure 1 - Water and organic solvent drying curve volatile organic solvent, two volatile solvents exist, example water and the volatile organic solvent itself. By measuring the weight change of treated wood during drying a combined drying curve results which After the individual drying curve is obtained for the reflects both water and organic solvent loss over volatile organic species, a diffusion coefficient can time. The trick is to separate individual water and be calculated using methods and equations estab- organic solvent drying curves from this simple lished by previous researchers. Such diffusion combined drying curve. The combined drying curve coefficients can be estimated for both radial and tangential directions Under normal kiln drying 80 ) conditions, longitudinal drying is considered negligi- 3 70 organic solvent uptake 3 ble compared to radial and tangential because of (l/m ) 60 30 long board length. 40 50 50 60 The diffusion coefficient is highly dependent on 70 temperature and can be calculated from empirical 40 80 drying curves obtained at different kiln temperatures 30 or estimated using further equations. Finally, know- ing the solvent diffusion coefficient, a surface 20 solvent evaporation equation can be solved to give volatile-organic-solvent drying weight-change (l/m Amount of organic solvent in Wood 10 curves for different initial uptake concentrations. 0 0 102030405060708090100110120 Time (hours) Thus, the final result is a series of weight loss curves (Figure 2), at different volatile organic compound uptakes and kiln temperatures, which allow estima- Figure 2 - Predicted solvent drying curve examples for tions of treated-wood organic-compound moisture kiln drying at one temperature for different initial content as a function of kiln drying time. organic solvent uptake levels

Forest Research results to date have shown good correlations between theoretical (modeled) and This model will be used to enable fast and accurate actual solvent drying results. Results have also solvent drying time estimations without the need for shown airflow to have less affect on solvent drying extensive, costly and time consuming research than temperature and are not included in the above experiments or costly gas detection equipment and method. Thus solvent drying can be modeled from specially designed kilns. theory to give good estimates of kiln drying times, for a variety of conditions, without the need for Full details about the model and equations used can extensive experimental trials. provided upon request to the author.

EQUILIBRIUM MOISTURE CONTENT, SHRINKAGE AND FIBRE SATURATION POINT OF EARLYWOOD AND LATEWOOD OF RADIATA PINE

Shusheng Pang and Rob Orchard

The three-directional anisotropic shrinkage of wood conditions (temperature and humidity) in-service (ie the different shrinkage properties in the tangen- and the associated shrinkage/swelling behavior of tial, radial, and longitudinal directions) is of critical wood also causes dimensional instability. Two other importance in lumber drying and in the use of wood factors - equilibrium moisture content (EMC) and products. We all know that below the fibre satur- the fibre saturation point (FSP) - are also related to ation point (FSP), wood will shrink or swell in wood drying and shrinkage. Therefore, a good response to changing moisture content, and that the understanding and description of wood shrinkage is extent of shrinkage or swelling differs for the three vital in order to minimise drying defects and to anisotropic directions (longitudinal, radial and improve wood stability in use. tangential). Normal wood shrinks and swells the most in the tangential direction and least in the Earlywood and latewood shrinkage information is longitudinal direction. However, differences exist also playing a critical role in our stress modeling between earlywood and latewood, between juvenile programme. With data on the differences in shrink- wood and mature wood, and between normal wood age between earlywood and latewood and the and compression wood. Non-uniform shrinkage strength properties of each component during drying properties are the major cause of drying-related (over a range of schedule temperatures) we hope to defects such as warp (bow, crook, cup and twist) be able to predict the drying stress by growth layers and residual drying stress. Fluctuations of ambient (rings), the strength of each layer, and its ability to 30 absorb the stress. From this we can predict Earlywood (Series1) the permanent stress set and degrade such 25 Latewood (Series1) as checking. In the longer term it is Earlywood (Series2) intended to use the shrinkage and stress 20 Latewood (Series2) data to predict warp of full length lumber. EMC table In the cu 15 In the current work, anisotropic shrinkage was measured for earlywood and latewood 10 samples of radiata pine dried to a range of 5 moisture contents from green to oven dry. Equilibrium moisture content (%) In addition, the equilibrium moisture 0 content and the fibre saturation points were 0 102030405060708090100 also investigated. In this study, a radiata Relative humidity (%) pine log was cut at breast height from a forest in the Central North Island, New Figure 1. Equilibrium moisture content of earlywood and Zealand. From this log, over 300 earlywood latewood of radiata pine (30°C). and latewood specimens were prepared to represent a trend from pith to bark. The 0.6 summarised results are presented below. For the detailed procedure and results, please 0.5 contact the senior author of this article. 0.4 Earlywood Latewood 0.3 Pith Equilibrium moisture content (EMC) The samples were equalised at 30°C in a 0.2 range of humidity from 0 (oven dry) to 95% RH. Below 80% RH latewood had a slightly 0.1 higher EMC value than the earlywood (by 0.1 to 0.6% mc) and of some surprise was Longitudinal shrinkage at 12% mc (%) 0 that the heartwood EMC was higher than that 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Growth ring number from pith to bark of the sapwood (by 0.2 to 0.6% mc). Above 80% RH, the latewood EMC was lower than Figure 2. Longitudinal shrinkage of earlywood and the earlywood (by 0.2 to 0.5% mc). However, latewood of radiata pine from pith to bark. the EMC difference between earlywood and latewood, and that between heartwood and sapwood were statistically significant. The measured EMC values were higher than those Table 1: Tangential shrinkage (%) averaged by wood type normally presented in books on wood (from green to mc% indicated) properties because the samples used in this work were dried from green. That is the Wood type Earlywood Latewood Overall readings were only for the desorption side of 12%mc O.D.* 12%mc O.D. 12%mc O.D. the EMC hysteresis curves, whereas data Heartwood 3.0 4.9 3.9 6.2 3.5 5.6 presented in the books represents the average Sapwood 3.4 5.9 3.8 6.6 3.6 6.3 values for the EMC hysteresis curves. Figure Overall 3.2 5.4 3.9 6.4 3.6 5.9 1 shows how the actual EMC varied with * Oven Dry humidity for earlywood and latewood Table 2: Radial shrinkage (%) averaged by wood type (from green to mc% indicated) Tangential, radial and longitudinal shrinkage The measured results for the three directional Wood type Earlywood Latewood Pith Overall shrinkage are summarised in the following 12%mc O.D. 12%mc O.D. 12%mc O.D. 12%mc O.D. tables and the profile of longitudinal Heartwood 1.9 2.3 3.2 6.3 2.5 4.3 shrinkage of earlywood and latewood from Sapwood 2.0 4.2 2.8 4.5 2.4 4.4 pith to bark is illustrated in Figure 2. Overall 1.9 3.2 2.7 4.9 2.1 3.3 2.3 4.1 Table 3: Longitudinal shrinkage (%) averaged by wood Fibre saturation point type (from green to mc% indicated) In general, the FSP of heartwood was higher than sapwood, and that of latewood was higher than earlywood. The overall average FSP value Wood type Earlywood Latewood Pith Overall for radiata pine was 29.1%, with values ranging 12%mc O.D. 12%mc O.D. 12%mc O.D. 12%mc O.D. from 25.0% to 32.8%. The average latewood Heartwood 0.29 0.52 0.26 0.44 0.27 0.48 FSP was 29.4%, which was slightly higher than Sapwood 0.14 0.23 0.15 0.27 0.15 0.25 that of the earlywood (28.9%). The FSP for the Overall 0.22 0.39 0.21 0.36 0.27 0.43 0.22 0.38 heartwood (29.6%) was 1% higher than the sapwood (28.6%). WOOD PROCESSING CONTACTS

AREA OF EXPERTISE NAME

Sawmill Economics & Optimisation Louw Van Wyk

Sawmill Improvement Peter Bayne & Quality Control

Scanning & Image Processing Peter Bayne

Log Quality / Grade Recovery John Roper / Don McConchie

Timber Grading / Timber Utilisation John Turner

Remanufacturing Jeremy Warnes

Wood Quality Don McConchie

Alternative Species (to radiata) John Roper / Russell McKinley / Wood Quality

Hardwood Sawing John Roper / Tony Haslett

Timber Drying Tony Haslett

Kiln Design / Kiln Control / Dryspec Steve Riley / Richard Dandoroff

Moisture Meters Ian Simpson

Antisapstain Treatments Robin Wakeling

Preservative Treatments Mick Hedley

Preservation Standards Mick Hedley

Environmental Technology John Gifford

Forest Research Phone: + 64 7 343 5899 Facsimile: + 64 7 348 0952 www.forestresearch.co.nz Wood Processing Forest Research Sala Street Private Bag 3020 Rotorua, New Zealand

Telephone: + 64 7 343 5899 Facsimile: + 64 7 348 0952 www.forestresearch.co.nz