BY W. E. COHEN
MOST of the forest areas of Australia occupy a narrow coastal belt extending from the southwest of western Australia to northern Queensland, as shown in Figure 1.
The outstanding feature of these areas is the over-woods, of which the dominating species are of the genus Eucalyptus. A typical example of one of its many species is shown in Figure 2.
Fig. 1. Distribution of main forest areas in Australia.
Fig. 2. A typical stand of Eucalyptus regnans in Southern Tasmania.
Softwoods, or non-pored woods, indigenous to the country occur in very small quantities. Even with the recent development of plantation-grown exotic pines, covering approximately 61,000 hectares (150,000 acres), the quantities of softwoods are quite inadequate to meet the demand for such timbers for purposes not including pulpwood. Consequently, it was realized long ago that if a pulp and paper industry was to be established in Australia, it would have to be based on the utilization of hardwoods and especially of eucalypts.
These circumstances have tested the resourcefulness of the Australian research worker.
Investigations in Australia, where until recent years there was no wood-pulp industry, have done much to destroy the old fallacy in papermaking - that good quality paper could be made only from long-fibered pulps derived from coniferous woods. Until a decade or so ago hardwood pulps, manufactured by the soda process, were used as "fillers" in book and magazine papers because their bulky nature lent softness and opacity to the sheet. Attempts to convert hardwoods to pulps for other purposes resulted in low yields of hard-to-bleach pulps which, because of the shortness of their fibers, were believed incapable of producing anything but a weak sheet.
The very name "hardwood," which is so misleading because some hardwoods are softer than some softwoods, probably played some part in creating this fallacy. In general terms, the pulping of wood involves the treatment of wood chips with certain chemical solutions at elevated temperatures and pressures so as to dissolve the fiber-encrusting materials, lignin and associated polyuronides, and to leave as a residue the isolated cellulose fibers and the associated hemicelluloses which are so essential to good-quality pulp. It was easy for the idea to grow that hardwoods require more drastic treatment than softwoods. Generally speaking, the reverse is the case. Hardwoods contain less lignin and require proportionately less chemical in pulping; hardwood lignin and other fiber-encrusting materials are more vulnerable to chemical agents than their softwood counterparts. The length of the hard wood fiber is approximately 1 mm.; that of softwood tracheids 2.5 to 3.5 mm. Their diameters, however, are in the same proportion and consequently the ratio of length to diameter is the same for both fibers. The ratio rather than the fiber length is all-important in determining many of a pulp's paper-making qualities.
Recognition of these points was the fundamental factor in the successful establishment of the Australian pulp and paper industry. Conversely, the failure to recognize them did much to hinder an earlier development of the hardwood pulp industry overseas. It has now been convincingly demonstrated that, by suitable treatment, hardwoods can be made to give high yields of easily bleachable pulp which, by appropriate conditions of beating, can produce high-class papers of almost any quality, except perhaps high tearing resistance.
Attention was first directed seriously to the subject in Australia as a result of the shortage of papermaking materials during World War I. By 1918 sufficiently promising results had been obtained to justify a grant from the Western Australian Forestry Department to carry out a more systematic investigation.
In 1920, the investigations were taken over by the Commonwealth Advisory Council for Science and Industry and were extended to cover timbers, principally eucalypts, from states other than Western Australia. A special laboratory was set up with equipment, largely improvised, but including a model Fourdrinier paper machine making a sheet 10 cm (4 in.) wide at the rate of about 1.2 m per minute (4 f.p.m.). This machine was purchased with a grant made by four newspaper companies in Western Australia. Small though it was, it was used to prove that pulp could be felted satisfactorily on a moving wire. Previously all sheets had been handmade and this introduced a personal factor which, in those days, was difficult to overcome. With the later development of standardized equipment and techniques for making laboratory handsheets, this machine has become more or less a museum exhibit although it has, on occasion, been used for publicity and educational purposes. It is shown in Figure 3.
In 1922 the first semicommercial tests were made at Geelong, Victoria. Here printings and writings were successfully made from 75 percent bleached soda eucalypt pulp and 25 percent imported long-fibered pulp on a 213-cm. (84-inch) machine at 46 m.p.m. (150 f.p.m.). By 1923 industrialists were taking an active interest. In 1924 and 1925, under the auspices of the Commonwealth Institute of Science and Industry, investigations began into the application of the sulphite process to eucalypts. In addition, an interested industrial group sent 200 tons of Tasmanian logs to Holland for mill-scale tests to determine- the suitability of eucalypts for newsprint production. These investigations gave satisfactory results, but they disclosed the need for further investigations to overcome certain difficulties.
In 1928 a complete pilot plant was erected at Kermandie, Tasmania. It included a digester for sulphite cooking, with a capacity of one cord of wood, a three-pocket grinder, an 86-cm (34-inch) fourdrinier machine, and all the required accessories. The experiments at Kermandie, which lasted about 2½ years, covered sulphite pulping, grinding, bleaching and decolorizing, and the conversion of pulps to several grades of paper. They were followed by large-scale runs on a 305-cm (120-in.) machine at Fairfield, Victoria. These demonstrated that eucalypt woods, subject to certain modifications of oversea practice, were amenable to grinding and that Eucalyptus regnans was superior to other eucalypts for this purpose. They demonstrated that standard equipment contained too much iron, which reacted with tannin to produce an off-white or greyish pulp and that it would be necessary to construct groundwood preparation equipment from materials that do not react with tannin.
Although these results were convincing enough, no immediate move was made to set up a full-sized plant. By 1934 some of the leading Australian newspaper groups became interested and formed the Derwent Valley Paper Co., under the auspices of which 100 tons of good quality E. regnans groundwood was prepared at the Kermandie pilot plant and shipped, along with a considerable greater tonnage of eucalypt woods to the Pacific Mills Co. at Ocean Falls, British Columbia, Canada. The groundwood was blended with a proportion of Ocean Falls long-fibered sulphite to yield a high-grade newsprint on a high-speed machine. Additional grinder runs on the eucalypt wood, together with the paper-making test, confirmed earlier experimental data obtained at the Kermandie plant.
Application of the kraft process in Australia began with some experiments on an exotic wood - plantation-grown Pinus radiata. These experiments, which were carried out by the Council for Scientific and Industrial Research reached the pilot-plant stage in 1927. Previously, research at Canton, North Carolina, U.S.A., obtained good results by blending eucalypt pulp, prepared by the sulphate process, with a proportion of longer fiber in the manufacture of book and high-grade papers, and they recommended this process. In 1932, the Australian Paper Manufacturers Ltd. turned its attention to the kraft process; preliminary laboratory tests on E. sieberiana gave highly promising results. Two years later, a small semicommercial plant was operated at Botany, New South Wales. In addition to confirming the earlier laboratory results, it proved that satisfactory runs could be obtained on the paper machine. The matter was then taken up in earnest by that company and by the end of 1937 a pilot mill, producing 10 tons of pulp a day, was in operation at Maryvale, Victoria. During the erection of this plant further laboratory studies were carried out, involving the variation within and between trees of E. sieberiana and the correlation of chemical and physical properties of the wood with its pulping properties. These tests were made by the paper company in co-operation with the Division of Forest Products, Council for Scientific and Industrial Research Bleached and unbleached krafts were produced at the Maryvale pilot mill, and were used in the various paper and board mills of the company in order to gain further experience in processing and utilization. The results, together with some apprehension about the imported raw-material situation, upon which the company's various mills were almost solely dependent, led them to embark without delay on the erection of a full-scale pulp mill, originally designed to produce 90 tons a day but subsequently increased to about 140 tons a day.
Research on the utilization of eucalypts for the production of industrial cellulose was really a product of World War II. Some attention was, however, given to this matter during the period already discussed. Now, twenty years later, considerable interest is being shown in the possibilities of eucalypts woods for this purpose. This matter is mentioned here because it harmonizes with the moral of the story just told, that it takes the greater part of a quarter of a century to overcome prejudice and conservatism in an old-established industry and that only under circumstances of emergency, such as a shortage of raw materials, can a new idea take root.
Allowing for recent expansion, the Australian pulp and paper industry represents a paid-up capital investment of more than £10,000,000. More than half of this industry has resulted directly or indirectly from research carried out in Australia.
There are three main pulp mills, each using a different process - soda, groundwood, and kraft. These are discussed briefly below.
Associated Pulp and Paper Mills Ltd. operates a soda-pulp mill at Burnie, on the northwest coast of Tasmania. The Company was inaugurated in 1936 with a paid-up capital of £1 500,000, which was doubled for the company's postwar expansion program. Production started in 1938 and operations were based initially on the original investigations using the soda process on eucalypt pulps. By means of research concurrent with its operations, this company has improved the quality of its products, the yield and cost per ton, and the overall output of its pulp mill. Pulpwood is drawn from eucalypt forests of northwestern Tasmania, the chief species being E. obliqua, E. gigantea, E. amygdalina, and E. viminalis. The mill produces a wide range of fine writing and printing papers, hard and soft-sized duplicating paper, blotting and cartridge paper. Some grades are furnished with 100 percent eucalypt stock and the over-all furnish averages 90 percent of bleached soda eucalypt pulp, the balance being imported long-fiber and non-fibrous materials. The mill produces its own caustic soda and chlorine in an adjacent electrolytic plant. Two paper machines are operated; a 457-cm (180-in.) machine with a maximum speed of 240 m.p.m. (800 f.p.m.) and a 229-cm (90-in.) machine with a speed of 120 m.p.m. (400 f.p.m.). Machine speeds of at least 190 m.p.m. (620 f.p.m.) are common with high-percentage eucalypt furnishes. A third machine is almost ready to go into production. The present rated output is 20,000 tons of paper per year and 18,000 tons of pulp per year. Because of shortages of labor and materials, the actual output is lower; 17,500 tons of paper were produced in 1946-47. During World War II this mill was the sole source of fine writing and printing papers for the whole of Australia.
Australian Newsprint Mills Ltd. operates a newsprint mill at Boyer, a small settlement 35 km (22 miles), from Hobart, Tasmania. The company was registered in March 1938 with a nominal capital of £4,000,000 of which £1,500,000 was paid up. Towards this amount, the Tasmanian Government loaned £250,000, which has since been repaid. Substantial amounts were invested by the proprietors of several leading Australian newspapers. Construction of the mill began early in 1939 and production started early in 1941. The mill (Figure 4), consisting of buildings costing £250,000 and equipment worth £650,000, is situated on the banks of the Derwent River. Much of the equipment was manufactured in Australia using, where necessary, materials that would not stain the groundwood by reaction with wood tannins.
The mill draws its pulpwood supplies from 1,000 km2 (400 square miles) of concession territory within 100 km (60 miles) of Hobart on the Derwent River and its tributaries. The wood is handled by the largest logging plant in Australia at the rate of 250 tons per day. Groundwood is prepared chiefly from old trees of E. regnans, but the woods of young trees of this species and of E. obliqua and E. gigantea are also used in smaller quantities. Wood unsuitable for grinding is used as fuel.
The groundwood plant is equipped with Australian-made grinders, using both natural and artificial stones. Groundwood, proportioned with approximately 17 percent of Canadian news sulphite, is made into newsprint on a 411-cm (162-in.) machine at speeds exceeding 300 m.p.m. (1,000 f.p.m.). Although the rated capacity of the mill is 30,000 tons per year, the output was actually 32,000 tons in 1946-47. During World War II, the mill's output was used in a pool which kept the Australian newspapers in circulation although they were of course drastically reduced in size. The printing qualities of newsprint depend mainly on the properties of the groundwood. The successful production of newsprint from E. regnans and, to a lesser extent, from other eucalypts, proves that their groundwoods have the necessary properties.
The Australian Paper Manufacturers Ltd. operates a kraft pulp mill at Maryvale, Gippsland, Victoria. This mill, which started production in 1939, has a capacity of 40,000 tons per year, of which 20,000 tons is bleached. Nine species of eucalypts are used: E. regnans, E. sieberiana, E. gigantea, E. eugenioides, E. obliqua, E. goniocolyx, E. capitellata, E. consideniana, and E. muelleriana. During the years following the disastrous forest fires of 1939, fire-killed timber was used in large quantities. Much of the eucalypt kraft is blended with imported long-fiber kraft and converted to paper on a 457-cm (180-in.) machine at Maryvale. The remainder of the mill's output is lapped and transported to other company-owned paper mills at Melbourne and Sydney. The company's total annual output of paper and board is 125,000 tons. It manufactures a variety of paper products in the furnish of which the eucalypt component varies from 35 to 90 percent.
Reference has been made to the co-operation between the Australian Paper Manufacturers Ltd. and the Division of Forest Products, C.S.I.R., in the application of the kraft process to E. sieberiana. In 1937, with the establishment of the two other companies and with production in sight, attention was turned to the future research needs of the Australian pulp and paper industry. Each company had set up its own research groups to handle problems specific to its own process and raw materials. But there was still a need for an organization to study fundamental problems of the industry as a whole. The industry looked to the Division of Forest Products to undertake this work. Since 1937, the work of the Wood Chemistry and Wood Structure sections of the Division of Forest Products, C.S.I.R., has been partly subsidized by grants from the Australian industry and, more recently, by Forest Products Ltd. of New Zealand.
The main object of this co-operative research work is to seek and disseminate fundamental information on the chemistry, physics, and structure of the hardwoods which serve as raw materials to the industry. Consideration is also given to the standardization of pulp evaluation methods 'end equipment, to the numerous fundamental factors which influence the processing of pulp, and the strength of a sheet of paper.
The Division of Forest Products has trained personnel and specialized equipment necessary for work of this caliber. One of the several laboratories devoted to this work. the pulp-evaluation laboratory, is shown in Figure 5. It has British standard sheet-making equipment, various types of laboratory beaters, stock dividers, which are used to sample pulp suspensions accurately, and accessory equipment.
Broadly speaking, the work is carried on under the following headings:
1. Structure of woods and of their tracheids and fibers.
2. Chemistry of wood polysaccharides.
3. Chemistry of lignin.
4. Methods of wood and pulp analysis.
5. Methods of pulp evaluation and paper testing.
Information on the structure of wood is fundamentally important to the wood-pulp manufacturer. Structure plays an important role in the penetration of pulping chemicals and determines the conditions that must be employed to secure a satisfactory cook. Structure also influences the amenability of woods to grinding.
Fiber structure is even more important. In order to be able to develop strength in a sheet of paper, pulp must be subjected to mechanical treatment to induce in the fiber structure certain modifications, such as fibrilation, the nature and extent of which are related both to the fiber structure and to the equipment required. Elucidation of the structure of the wood-pulp fiber and of the physical changes it undergoes in processing is being undertaken in order that the Australian pulp and paper industry may understand more clearly what it is doing or has to do to its fibrous raw materials.
Abnormalities in wood structure such as reaction wood, brittle heart, slip planes, and minute compression failures give rise to abnormal wood-pulp fibers. Information on causes and effects is invaluable in the selection of pulpwood, especially ¡that intended for the manufacture of groundwood.
Chemical pulping of wood involves the recovery of cellulose and some associated polysaccharides with the simultaneous removal of some or all of the lignin and some polysaccharides. The chemical makeup of wood substance is far from clear. It has not been proved, for instance, that chemical bonds exist between lignin and cellulose, between cellulose and its associated hemicelluloses, or between lignin and hemicelluloses. Proof or otherwise of the existence of such bonds and information on their susceptibility to chemical reagents would lead to a clearer understanding of pulping processes. Likewise a more intimate knowledge of lignin and its reactions would not only facilitate the development of more rational pulping processes but could lead to the exploitation of lignin as a natural raw material. At present it is largely a waste product of pulp mills. The recovery of industrial cellulose from wood involves not only pulping and bleaching but also chemical methods of refining to rid the cellulose of associated polysaccharides. It is not known with certainty whether these polysaccharides coexist with cellulose in the form of mixed crystals, or as mixed chains, or whether their relationship is chemical or physical in nature.
Research on eucalypt wood lignin is being actively carried on by the Division of Forest Products to provide the pulp and paper industry a clearer concept of the chemical composition and reactions of this material. For this purpose, methanol lignin, prepared by extracting wood meal with methanol at 150°C., is used because it is considered to resemble more closely the natural lignin than lignin products isolated by other methods.
The association of cellulose and other polysaccharides in wood is being studied by fractionating holocellulose (i.e., wood tissue from which only lignin has been removed) and by studying the molecular weight frequencies of the various fractionation residues. It has been shown that removal of pentosans results in a decrease of the average molecular weight with the polymerization degree frequency shifting to a zone of lower polymerization. This could be taken as proof of the existence of mixed chains, the removal of pentosans resulting in a shortening of chain length. However, there is still the possibility of degradation of pure cellulose chains by the reagent employed for the removal of adjacent pentosan chains. Hence the picture of the cellulose-hemicellulose relationship is far from clear and is still being actively studied.
Methods of wood and pulp analysis are essential to the assessment of woods and pulps in the control and development of pulping processes. For the profitable use of information exchanged on such matters it is essential that methods be standardized. In collaboration with the industry, the Division of Forest Products has investigated, improved, and finally adopted standard methods. Some of these differ from those employed elsewhere, in particular the methods of sample preparation, the holocellulose determination, the pentosan determination, and improvements in the methods for determining Cross and Bevan cellulose, lignin, and various extractives.
The buying and selling of pulp and paper, the development or improvement of pulping processes, and the control of pulp and paper manufacture depend on methods for evaluating pulp and testing paper. A thorough study has been made of the variables of laboratory beating equipment and methods, of handsheet making, and of paper-testing instruments and methods. Laboratory pulp testing is facilitated by accurate sampling of pulp stock; for this purpose special equipment known as stock dividers has been designed and developed. These are now in use throughout the Australian industry and other countries are showing an interest in them. In collaboration with the industry and with a Melbourne instrument technologist, the division has developed an accurate instrument for measuring the internal tearing resistance of paper. This instrument is now standard throughout the industry and models are soon to be exported, and it is expected that the instrument will find more general application.
The results of all investigations related to the pulp and paper industry and carried on by the Division of Forest Products are discussed annually at Pulp and Paper Co-operative Research Conferences. These are held in rotation in Burnie, Hobart, and Melbourne, and are attended by research personnel from industry and from the division. In recent years, papers on the results of investigations carried out in the industry itself have been contributed and discussed. The reports given at these conferences, together with the informal discussions which follow, are reproduced and distributed throughout the world on a restricted scale.
Arising from these conferences is the co-operative purchasing scheme. This not only concerns the regular purchase of laboratory stores to ensure that each party uses materials of identical grade and quality, but also the design, purchase, testing, and correlation of new equipment.
These conferences, continued since 1939, have brought together a limited group of the technical personnel of the pulp and paper industry. By 1945 it was felt that the conferences had been so successful that a similar opportunity for exchange of ideas should be extended to all technical personnel. A provisional committee was formed in 1946, and early in 1947 the Australian Pulp and Paper Industry Technical Association held its First Annual Meeting and First General Conference in Melbourne. The Second Conference was held this year in Hobart, and plans are maturing for the Third Conference in Sydney, New South Wales, in February 1949. The association publishes its proceedings, the second volume of which is now in the press.
World War II gave the Australian pulp and paper industry an opportunity to mature rapidly. The country's sole dependence on the industry's products did much to overcome the prejudice usually shown toward new products. Both the trade and the consumer soon became accustomed to papers made from eucalypts. Initial success has stimulated the industry to expand. The caliber of eucalypt pulps has become well known abroad, and oversee capital is being attracted to the industry.
The Associated Pulp and Paper Mills Ltd. is installing two new paper machines with accessory equipment and is enlarging its soda pulp mill. By 1951, the output of fine printing and writing papers is expected to exceed 30,000 tons a year. The company, in association with Thomas Owen & Co. Ltd. Of England, recently registered Thomas Owen & Company (Aust.) Ltd. with a nominal capital of £3,000,000. This new company will establish a second paper mill at Burnie, Tasmania, for the manufacture of vegetable parchment, greaseproof, glassines, and other specialty papers. Eucalypt pulp and utility services will be supplied by the Associated Pulp and Paper Mills Ltd., and a large proportion of the equipment and technical assistance will be provided by Thomas Owen & Co. Ltd.
A further development is the subject of negotiation between this new company and the British Coated Board and Paper Mills Ltd. It is proposed to establish at Ballarat, Victoria, a mill for the production of coated papers based on eucalypt pulps. The operating company will be Ballarat Paper Mills Pty. Ltd. with a nominal capital of £1,000,000. Special equipment will be imported.
The Australian Newsprint Mills Ltd. is enlarging its groundwood plant by installing ring grinders. A 625-cm (246-in.) paper machine is shortly to be assembled. The company expects to produce 80,000 tons of newsprint a year by the end of 1950.
Reference has already been made to Australia's lack of long-fibered softwoods. It has been necessary to import long-fibered pulps, mainly from hard-currency countries. Prices went up 70 percent over a recent period of 12 months. Attention has therefore been turned to the softwood resources of New Zealand. In the government and private forests of that country, plantation-grown Pinus radiata occupies an area of nearly 200,000 hectares (500,000 acres) and it is estimated that these forests are capable of yielding 2,600,000 m3 (1,000,000 cords) a year. New Zealand Forest Products Ltd., whose P. radiata resources occupy 61,000 hectares (150,000 acres), operate four sawmills. The slabs from some of these mills are converted to insulating and double-faced hardboards for building purposes.
This company has established a research laboratory, which investigates the suitability of its raw material for various grades of pulp. Pilot-plant experiments have been carried out in the United States and have demonstrated that New Zealand-grown P. radiata yields kraft pulp that can meet the rigid specifications for multi-wall bag paper. A multi-wall bag plant has been established, but it is now using imported paper. When the pulp and paper program of the company is further developed, raw material for this plant will be made from P. radiata.
The company is establishing a kraft pulp mill after the designs of K.M.W. of Karlstad, Sweden. Originally, the capacity of this plant was to have been 10,000 tons per year but it was recently announced that a further £800,000 is to be used to increase its capacity to 25,000 tons. Half of the output will be shipped to Australian Newsprint Mills Ltd., for proportioning with eucalypt groundwood in the manufacture of newsprint.
The New Zealand State Forest Service has arranged: trials of P. radiata in co-operation with the three main Australian pulp and paper companies to investigate the manufacture of kraft pulp and its proportioning with eucalypt kraft, soda, and groundwood pulps. The Forest Service has under consideration the erection of a large integrated plant consisting of sawmills, groundwood mill, kraft pulp mill, and newsprint mill. If the grinding is confined to sapwood and the resinous heartwood is not used, it has been demonstrated that a good grade of newsprint can be made. P. radiata has been ground for some years for cardboard manufacture by another New Zealand Company - Whakatane Paper Mills Ltd., which produces 12,000 to 15,000 tons of board per year.
Expansion plans of the Australian Paper Manufacturers Ltd. encompass the improvement of existing plant and the installation of new units to meet the increasing demand for board and paper products. Expansion plans for the industry as a whole also envisage better and more efficient utilization of its wood resources by means of the integration of pulping with sawmilling, peeling, and the manufacture of building boards. Reduction of waste by means of efficient barking-methods is also contemplated; hydraulic barking equipment will shortly be installed by Associated Pulp and Paper.
A large and thriving industry, based-on the utilization of eucalypt hardwoods for the manufacture of high-quality papers of all grades, has been established in Australia as the result of research which extended over a quarter of a century.
Although eucalypt fibers are short, they are proportionally thin and consequently their felting properties are not impaired. They have a far more important use in papermaking than that of the usual run of oversee hardwood pulps, which are used largely as " fillers. " Newsprint furnished with eucalypt groundwood possesses excellent printing properties which, rather than strength, are the most important criteria. Mild cooking methods preserve the high pentosan content of chemical eucalypt pulps, which is responsible for the case with which they are processed and for improvement to the formation and finish of the eucalypt-furnished sheet.
Eucalypt pulps make their full contribution to the bursting and tensile strengths of a paper. Their contribution to tearing strength is not inconsiderable but, in papers where a high resistance to tearing is desirable, it is usual to develop this property by proportioning eucalypt pulp with long-fiber. Australia lacks softwoods from which to derive long-fibered pulps and has had to import them from the Northern Hemisphere. New Zealand will soon supply Australia's long-fiber needs from plantation-grown P. radiata.
AUST. PAPER MFRS. LTD. Wood Pulps (Brochure). Melbourne (1944) Maryvale. Pp. 2-4.
AUST. PULP PAPER IND. TECH. Assoc. (1947). Proceedings, Vol. 1.
BENJAMIN, L. R. (1923) "The Manufacture of Pulp and Paper from Australian Woods," Inst. Sci. and Ind. (Aust.), Bull. 25 (out of print).
____. (1927) "Newsprint: Preliminary Experiments on the Grinding of Immature Eucalypts for Mechanical Pulp, and Possibilities of Manufacturing Newsprint in Australia." Coun. Sci. Ind. Res. (Aust)., Bull. 31 (out of print).
____., and J. L. Somerville. (1928) "Paper Pulp and Cellulose from Eucalypts by the Sulphite Process," Coun. Sci. and Ind. Res. (Aust.), Bull. 37 (out of print).
BOAS, I. H. (1947) " The Commercial Timbers of Australia; their Properties and Uses.'' Coun. Sci. Ind. Res. (Aust.), (Govt. Printer, Melbourne), p. 106.
CAVANAGH, J. C., H. E. DADSWELL, A. W. MACKNEY and T. M. REYNOLDS. (1938) "Study of the Pulping Properties of Three Trees of E. Sieberiana, using the Sulphate Process." Coun. Sci. Ind. Res. (Aust.), Pamphlet 86.
COHEN, W. E. (1943) "Hardwood Pulps for Papermaking." Paper Makers' Assoc. Tech. Sec. Proc., 24:354-357.
PULP AND PAPER CO-OP. RES. CONF. (AUST.), Proceedings 1st-8th Conf., 1939-1947.
Photos accompanying this article were furnished by the Council for Scientific and Industrial Research Commonwealth of Australia.
