Wood materials having their moisture measured with electrical moisture meters have various thicknesses. And the electrical moisture meter reading is affected by the differential thickness of wood materials. This effect was tested on some electrical moisture meters.
   The effects of thickness of thin wood materials, wood board plywood and veneer, upon the moisture meter reading is so remarkable not only on high frequency type meters but also on resistance type meters, that the effect can not be neglected. It follows, therefore, that moisture measurement with electrical moisture meters of thin wood materials must be carried out with care, and due consideration given to their thickness and property of support table.

   Under the constant drying condition we made experiments on the drying of plywood, especially the drying process, evaporating- and drying velocity, moisture diffusion in plywood and elevating process of surface and inner temperature of plywood. The plywoods used are as follows; 1) veneer: birch wood (thickness 0.5mm) and lauan wood (thickness 1.5 mm), 2) construction: 3-ply and all layers perpendicular with each other, (a) A-plywood: outside layer-birch veneer, center layer-lauan veneer, (b) B-plywood: outside and center layer, birch veneer, 3) adhesive: urea-formaldehyde resin, 4) spreading: 40 g/ft², 5) pressure: 10kg/cm², 6) temperature: 100°C, 7) time: 10min, 8) specimen: 25×25cm, thickness: A-plywood 2.7±0.1mm, B-plywood 1.9±0.1mm. The test pieces of about 5×5 cm were coated with urea-formaldehyde resin to prevent the drying from four side faces and then soaked in water until saturated (initial moisture content: A-plywood 92∼120%, B-plywood 66∼98%).
   Results obtained are as follows;
   1) The drying process (moisture content u: drying time z) of A- and B-plywood are shown in Fig. 1 and the relationship between logu and z in Fig. 2. From these we can obviously recognize the three periods of constant rate, first and second stage of falling rate of drying.
   2) The elevating process of surface and inner temperature of plywood during drying are shown in Fig. 3 and 4. We can recognize the three periods concerning elevating process of temperature (i.e. heating, constant and elevating period of temperature by R. KEYLWERTH) .
   3) From Fig. 2, the first formula indicated by R. KELWERTH (du/dz = -K(u - u_eq) seems to apply to the results of our experiments (Fig. 5). Coefficient K and its reciprocal 1/K are given in Table 2.
   4) The relationship between the evaporating velocity dw/(A · dt) and average moisture content u are shown in Fig. 6. The surface evaporating coefficient (K) in the constant rate of drying of plywood (A- and B-plywood) was K = 3.7×10^-3g/cm² · h · mmHg (Fig. 7) and relationship between the rate of effective evaporating area A' to total surface area A, A'/A and u (%) are shown in Fig. 8.
   5) The relationship between the v_av/v₀ (v_av = u_m - u_eq, v₀ = u₀ - u_eq, u_m = average moisture content) and t/(a/2)² (t = drying time, a = thickness of plywood) of A- and B-plywood are shown in Fig. 9. It seems, consequently, that the general diffusion formula ∂u/∂t = K(∂²u/∂x²) can apply to the drying of these plywoods. Then we find the coefficient K (moisture diffusivity), λ(≈ (K' · r₀)/100, diffusion constant) and K₀ [K₀ = K(a/a₀)^n-2, n = 1.0 - 1.5, a and a₀ = thickness of plywood] of A- and B-plywood which are shown in Table 3.

   The purpose of this paper is to describe the effective control methods of end splits during drying of veneer.
   With the practical application of the Coe type roller dryer, tests have been carried out with the following veneers of beech having a thickness of 1.0 mm, width 76 cm, and length 227 cm, and a comparison made with similar materials that have had no treatment (A).
   (B) pasting on the side end with kraft paper of 1" width,
   (C) pasting on the side end with SS tape of 1/2'' width,
   (D) sewing of the end part by veneer sewing machine.
   Regarding the results obtained.....the number and length of end splits on veneers after being dried are shown in Table 1 and 2, and those of end openings on plywoods which were prepared with testing veneers, are given in Table 3. Judging from the data in Table 3, the sewing-treatment was the most effective in controlling end splits, and other pasting treatments were also effective compared with the case of no treatment.

   The writers studied the differences of gluing strengths of blood constituents used for plywood gluing, and now report the results of the study here.
   The materials used for this study were dried powder of a horse's whole blood, and some fractions separated from the blood, such as defibrinated blood, blood corpuscle, hemoglobin, serum, albumin, and globulin.
   Plywoods were glued with the glue mixtures prepared by adding 20 cc of water to 10 gr of the materials, and then the normal gluing strength of the plywoods, were compared.
   The experiments were carried out by the method of two-way layout having two factors, namely, glue materials (D), and pressures applied (A), and repeated three times.
   The following results were obtained in these experiments:
   1) The gluing strengths of globulin and hemoglobin are considerably greater than that of albumin.
   2) It seems that the gluing strength of blood corpuscle does not differ from that of hemoglobin.
   3) The gluing strength of serum is nearly equal to that of albumin.
   4) The gluing strength of defibrinated blood is much greater than that of serum, and less than that of whole blood.
   5) When plywoods are glued, the more pressure is added, the stronger gluing strength becomes; but it seems that there is interaction between the glue materials and the pressure added.

   In this paper the writers wish to report the results obtained from studies on the gluing strength and water resistance of plywood glued with solutions having pH of the isoelectric points of blood proteins such as albumin (isoelectric point, pH 4.8), globulin (isoelectric point, pH 5.4), and hemoglobin (isoelectric point, pH 6.4), and with solutions having pH of both sides of respective isoelectric point as above mentioned.
   Moreover, the writers experimented to ascertain whether the gluing strengths of serum glue and defibrinated blood glue had any influence on pH of the isoelectric points of the above mentioned proteins or not.
   The samples used in these experiments were dry powders separated from horse blood.
   The results obtained from these experiments were as follows:
   1) The solution having pH of the respective isoelectric point of the blood proteins such as albumin, globulin and hemoglobin have higher gluing strength and water resistance than the solution having pH of both sides of the respective isoelectric points.
   2) It seems that the gluing strength of serum glue and defibrinated blood glue are not influenced by pH of each isoelectric point of the proteins.
   3) The writers noted that the defibrinated blood glue seems to have as high a gluing strength in the acid side as seen in the alkali side.

   If, as is usual, the plywood is made from a single species, and the grain directions in alternate veneers are at right angles, then the elastic constant E at an angle to the grain are given theoretically by the equations, (2.5) in tension and (2.8) or (2.9) in bending, in terms of the basic constants of all the veneers in the plywood (i.e. the Young's modulus parallel to the grain E_L = E₀ ; the Young's modulus perpendicular to the grain E_T = E₉₀ ; the rigidity modulus G_LT ; the Poisson's ratio μ_LT).
   The basic constants (E_L, E_T and G_LT) and their ratios (κ = E_L/G_LT and Ω = E_L/E_T) of the veneers in the plywood were determined by the tensile tests of the strips, as shown in Fig. 3, and lie at the angle Θ with the grain in the outer plies of the sheet, for the values of Θ: 0°, 45° and 90°.
   The specimens were conditioned in the room at 20°C and 75 per cent humidity and the measurements were carried out in the conditioning room in the Forest Experiment Station. The construction of test plywood is shown in Fig. 1, and the moisture contents u, specific gravities Ru and the thickness values in Table 1. The method of cutting the specimens is shown in Fig. 2.
   The Young's moduli determined by the tensile tests are as follows (see Table 2):
   solid wood (Japanese basswood; Tilia japonica SIMK.)
   at  0° E_L = 67.8 × 10³kg/cm²
      45° E₄₅ = 11.8 × 10³kg/cm²
      90° E_T = 17.2 × 10³kg/cm²
           κ = E_L/G_LT = 19.1
           Ω = E_L/E_T = 3.94
 where     μ_LT ≈ 0.5
            G_L ≈ E₄₅/(4 - E₄₅/E_T)
   The calculated curve in Fig. 4 was obtained from the equation (2.2) using these basic constants. In the case of Young's modulus in tension at grain angles up to 90°, the experimental results agree well with calculated curve from the equation (2.3) as shown in Fig. 5.
   In the case of Young's modulus in bending, the agreement with the calculated curve from the equation (2.9) is also approximately close as in Fig. 7.

   Durability of foaming urea-resin glued plywoods and the common extended urea-resin glued plywoods have been studied. Durability test was carried out by using an open-type weather meter. One group of test samples was of standard shear test size, the other 8 × 15 cm size. The former test pieces were exposed for 0, 24, 48, 96, 144 and 216 hours, the latter for 0, 24, 96, 216, 336 and 432 hours.
   Table 1 illustrates the components of the glue and the condition of making plywoods. Fig. 1 shows the adhesive strength of the test pieces taken from the 8 × 15 cm samples, and Fig. 2 shows that of the standard shear test pieces.
   The results obtained are as follows:
   1) For the purpose of estimating the durability of glue joint, the smaller size sample was found to be suitable for the weather meter test. The adhesive strength of the larger size (i.e. 8×15 cm) does not fall so rapidly that it takes considerably long time to gain an appreciable fall as shown in Fig. 1.
   2) There was not any remarkable difference upon the durability between the foaming urea-resin glued plywoods and that of the common extended urea-resin glued.
   3) As regards the wood failure, the excellent durability of urea-melanin-condensated resin glue is preferably to that of urea-resin glue.
   4) Appreciable differences between wheat powder and soybean powder as the suitable extender could not be recognized in the small quantity used of them.

   This paper describes how the plate shear test shall be applied in measuring the shearing moduli of plywood, hardboard and particle board. A series of experiments were conducted with square plates loaded at corners just as the ASTM Standard test procedure to check the accuracy of the theory of isotropic plates.
   An experimental arrangement was prepared as shown in Figs. 1 and 2, to apply four equal loads at the corners of a square plate, two loads at the extremity of one diagonal acting downward, and two at the extremity of the other diagonal acting upward.
   From the theory of isotropic plate, the following equation is introduced, in which w is the deflection at |he point of the distance u from the center on the diagonal,
                  w = (3Pu²)/(2Gh³)
where, P is the total load applied to corners, h is the thickness of the plate, and G is the shearing modulus.
   It follows that
                  G = (3u²P)/(2h³w)
   The physical properties and Young's moduli of test boards are shown in Table 1.
   The test results are as follows:
   The relation between the shearing modulus and the ratio of length of edge a to thickness of the specimen h are shown in Figs. 3, 4, 5, and 6.
   These indicate that the values of shearing moduli are calculated from the equation affected by the length-thickness ratio a/h.
   It might be reasonable to make specimens have values of the ratio within 20 - 50.
   Generally speaking, this measuring and calculating method of shearing modulus might give satisfactory results for hardboard and particle board, but there are several disturbing factors inherent in plywood such as ply-construction, quality of veneer and the glue used.

   The purpose of this report is to present a method for determining the apparent Young's moduli of a multilayer plywood of symmetrical construction. If the plywood is made from a single species, and the grain directions in alternate veneers are at right angles, then the apparent Young's modulus E'_Θ at an angle to the grain are given theoretically by the equations (5) in tension and (6) in bending, in terms of the basic constants of all the veneers in the plywood. In the case now reported, the basic constants and their ratios of the veneers in the plywood were determined from the equations (3) and (4) by the tensile or bending tests of the strips, as shown in Fig. 3 of the preceding report, and they lie at the angle Θ with the grain in the outer plies of the sheet, for the values of Θ: 0°, 45° and 90°.
   In order to determine the basic constants from the equation (3) the following two relations are assumed:
         E₄₅ = 2E_T
         G_LT = E₄₅/(4 - E₄₅/E_T²⁾
     in this
         E_T≈G_LT≈E₄₅/2
   The constructions of test plywoods (3-, 5- and 7-ply plates of the same Lauan) are shown in Table 1, and the dimensions in Table 2.
   The test results in tension and bending are shown in Tables 3 and 5, and the basic constants are as shown in Table 4.
   The calculated curves in Figs. 1 and 2 were obtained from the equations (5) and (6) using these basic constants.
   The calculated Young's moduli of test plywoods, in the both cases of tension and bending, agree well with the observed one.

   Continuously since publication of the previous report, effects of the pressing condition, the thickness of the veneers, an assembly method of them and quality of the core veneers for the surface checking of plywoods have been investigated by utilizing the weather meter. Species of the veneer are Shina (Tilia japonica SIMK.) and Sen (Kalopanax septemlobus SOIDZ.) and quality of the veneers used in this experiment and surface appearance of the plywoods after the weather meter test are shown in Table 1, Fig.1 and Fig. 2.
   The results obtained are as follows:
   (1) In accordance with diminution of thickness, the difference of the surface checking in the case of exposing a tight side of the face veneer and in the case of exposing a loose side will be scarcely recognized, the reason being that the thinner the veneer, the less the difference of the surface qualities between a tight side and a loose side.
   (2) In the case of using 0.4mm or 0.2mm face veneers, the wavy undulations perpendicular to the grain of the face veneer have been recognized on them by means of the core veneer quality especially in the latter veneer (0.2mm), and sometimes these undulations cause the surface checks to occur and moreover, the dulamination of the face veneer, the reason being that the thinner veneer cannot overcome the stress of shrinking and swelling or the influence of the surface irregularity of the core veneers. In the case of 0.75mm or 1.0mm veneers, no appreciable difference could be recognized as in the case of 1.36mm veneer in the previous report.
   (3) Sen veneer is noticeably apt to grow surface checks and is sensitive to the pressing condition owing to the presence of large vessels and the irregular shrinkage of the part surrounding them. Generally, as regards the surface checking, the effects of the pressing condition is not more dominant than that of thickness of veneer, the assembly method, and quality of the core veneers.

   This report deals with the results of adhesive strength and water resistance of hot press plywoods bonded with urea formaldehyde resin (trade name, Uloid No. 22) mixed with blood glues or with the blood glues mixed with urea formaldehyde resin, the effect of amount of acidic hardener added to the mixed glue, its pot life and aging of the film obtained by spreading the glue mixture.
   With the urea formaldehyde resin mixed with a small amount of blood glue, we recognized neither remarkable deterioration nor notable promotion in gluing strength and water resistance as compared with those of unmodified resin, Uloid No. 22.
   However, those of plywood bonded with blood glue mixed with a small amount of urea formaldehyde resin were not better than those of the blood glue only.
   But it seems that a considerable addition of the blood glue to urea formaldehyde resin improves remarkably the boiling water-resistant property of the plywood; however, it drops according to the decrease of the amount of the blood glue.
   And then we recognized, within the limit of this experiment, that the adhesive strength and water resistance of plywood did not depend on the amount of acidic agent (NH₄Cl) used as a hardener.
   One of the effects of adding blood glue to urea formaldehyde resin was to prolong the pot life of the glue mixture, and the other was to improve the aging property of the glue film.

   Wood preseratives should have protective effects against attack by fungi, insects or marine borers. This paper deals with the evaluation of chemical substances against insects and fungi. Laboratory tests against insects were carried out using Leucotermes speratus, Coptotermes formosanus and Dinoderus minutus. Stake test was tested against Coptotermes formosanus in Kyushu district. These experiments were aimed at determining the combined action of contact, respiration and digestion poison of the chemicals. The wood block method described in JIS A 9302 was applied for comparing the preserving effectiveness against Poria vaporaria using Japanese cedar and four kinds of foreign wood. The prevention of mold growth on the test blocks was tested against Penicillium citrinum and Aspergillus flavus using cedar, lauan, ramin, plywood and soft board.
   The results obtained are as follows:
   1) Dieldrin was effective in protection against attack by insects.
   2) Tributyltin oxide and the preservatives containing three valency arsenic oxide and zinc or copper compound were very effective for protection against decay. Mixed solution of solubilized pentachlorophenol and dissolving zinc fluoride and arsenic trioxide in water that had been acidified with acetic acid had a good preserving effect against decay.
   3) Decaying resistance of four kinds of foreign wood was more durable against Poria vaporaria than Japanese cedar.
   4) In the cases of insecticides (emulsifiable concentrates), the inhibitory effect against fungi was quite poor. It was observed that the inhibitory concentration against molds was variable depending upon the kinds of test blocks.

   1) In this report are presented the results of a mathematical analysis of stiffness problems for Wooden Box-Beam under a few types of loading.
   The deflection of bending is obtained by the use of elastic strain energy function. From that

in the case of center-loading, end support, equation (4.1) is, if it is integrated for several integral variants x, y, z according to Fig. 1 and 3,

             where  P = the load applied to center of Box-Beam.
                     δ = the deflection of center of Box-Beam, (max. defl.)
   2) The wooden Box-Beams used in a preliminary experiment were constructed with Flange of Yezomatsu and web of 3 ply Lauan plywood (L, T, LT = 45° as parallel, perpendicular, and 45° respectively, to the grain of the face plies).
   3) In the case of center-loading test the theoretical value δ/p calculated from equation (5.1.2) was almost the same as the experimental ones, and the agreement between experiment and theory can be regarded as reasonably satisfactory. (Fig. 7)

   Impact bending test was worked out with the view to studying the effects of temperature on the mechanical properties of wood. The experiment was carried out at various temperature in the range from +60°C to -60°C, with hot water for the range higher than room temperature and with ethyl-alcohol bath and dry-ice for the lower range. Ash, spruce, Hinoki and animal-glued Kaba-plywood are the kinds of wood tested. It has been made clear through this experiment that, within the above temperature range, absorbed energy in impact bending test had a minimum value at a point between +10°C and -10°C, with each test piece of loading directions tangential, radial or 45° to annual rings for Ash, Spruce and Hinoki, but at about -30°C for animal-glued Kaba-Plywood. Equivalent bending strength increased linearly with the decrease of temperature for Ash, Spruce and Hinoki, but it appeared a minimum value at about -30°C∼-40°C for animal-glued Kaba-Plywood.

   The authors have studied the shearing modulus of lauan plywood and hardboard by the panel shear test. The test has been done conforming to the ASTM method. Test specimen is shown in Fig. 1. The experimental arrangement was prepared as shown in Figs. 2 and 3. The physical properties and Young's moduli of test specimens are shown in Table 1. The results obtained are summarized as follows.
   1) As shown in Fig. 5, the load-strain curve varies considerably according to the location of the wire strain gauge on the test board. Wire strain gauges pasted parallel to the direction of the load indicate compressive strains and gauges perpendicular to the direction of the load indicate tensile strains.
   2) As shown in Fig. 6, the strain in 45° to the direction of the load is so small comparing with the strain perpendicular to the direction of the load that it may be negligible.
   3) From the theory of isotropic plate, the following equation is introduced.
          
here,
        f_s : shearing stress (kg/cm²),  ε :   strain in diagonal direction of specimen,
        P  : total load (kg),                       G :   shearing modulus (kg/cm²),
        L_s : length of the side of specimen (cm),   t :   thickness of specimen (cm).
   We obtained the following equation.
          
   4) Shearing moduli calculated from the test results are shown in Table 2. The value of shearing modulus of hardboard is unexpectedly large and shows much dispersions.
   5) The load-strain curve of hardboard is divided into two straight lines as shown in Figs. 7 and 8, therefore some different values of shearing modulus is obtained according to curve divisions.

   In the previous paper, the authors reported that the load-strain curve of hardboard measured by the ASTM method of panel shear test was composed of two straight lines which had different inclinations as shown in Fig. 2. In this paper we describe our investigations into the cause of such result and report the following observations:
   1) There is no sudden change of the loading rate during the test, as shown in Fig. 3.
   2) There is no slip between the reinforcing block and the specimen during the test in the normal way. The effect of degree of tightening of block and specimen is indicated in Figs. 4, 5 and 6.
   3) With the loading, the specimen develops some bending deformation in the direction perpendicular to the surface of specimen as shown in Figs. 8 and 9. This fact is taken to be the cause of the irregular form of the load-strain curve.
   4) A load-strain curve of plywood in which the load direction is perpendicular to the grain of face veneer is shown in Fig. 10.

   In Sweden, the LARSSON-WÄSTLUND method (LW method) has been applied for the shear test of plywood and fiberboard. We described in this paper, procedures in which the LW method was improved to some extent and by which method the shearing moduli of plywood and hardboard were measured. Test specimen is shown in Fig. 1. The experimental arrangement was prepared as shown in Fig. 2 and 3.
   The results obtained are summarized as follows:
   1) The load-strain curve obtained by this method is normal as shown in Fig. 4, in contrast to the curve by the ASTM method which is composed of two straight lines as reported in the previous paper.
   2) The value of the shearing modulus by this method indicates less dispersion than the one by the ASTM method does.
   3) The shearing modulus obtained is much smaller than that by the ASTM method.
   4) The shearing modulus of plywood has some relation to the thickness of the board, that is, as the board becomes thinner, the value becomes larger.

   The subject of this report is to decide to what extent melamine fortifies the wood adhesive of U-F-resin.
   The results are as follows:
   1) Melamine fortifies the wet shear strength of plywood, especially its durability in boiling water.
   2) But an excess of melamines added in resin reduces the shear strength of plywood, that is, the optimun content of melamine needed to get the maximum strength is nearly in proportion to that of uncondensated formaldelyde in U-F-resin.
   3) Then it is permitted that the cohesion in cured adhesive is so fortified that the increasing of swelling degree of cured resin is defended by added melamine.
   4) As a fortified adhesive, urea-melamine-formaldehyde co-condensated resin is more effective than the addition of crystalline melamine, trimethylol melamine in adhesive solution.
   Most of the above results are obtained by the method of measuring the shear strength of plywood, tensile strength and swelling degree of cured resin-film in the case of immersion in water under various conditions.

   The effects of temperature on the static strength and the modulus of elasticity perpendicular to grain must be considered in the various problems of wood-working processes, especially those of plywood, improved wood and kiln drying.
   This paper deals with the effects on the compressive strength σ_p: stress at proportional limit, σ_2.5: stress at 2.5% strain, σ_5.0: stress at 5.0% train) and modulus of elasticity in compression (E) in tangential direction.
   The test pieces (cross section: 2×2 cm², length: 4 cm) of Hinoki (Chamaecyparis obtusa) and Buna (Fagus crenata) were used. The investigations were conducted at temperatures of 30, 45, 60 and 75°C under the nominal moisture contents of 7, 13, 18, 24% and green.
   The results obtained are as follows:
   1) The stress-strain curves were approximately linear in a range of small strain, and the range grows narrower with the increases of temperature and moisture content (Fig. 1).
   2) The values of σ_p, σ_2.5, σ_5.0 and E decrease almost linearly with the increase of temperature (Fig. 2∼5) and the temperature coefficients show maxima at a moisture content of 18∼20% (Table 3).
   3) The percentage changes in σ_p, σ_2.5, σ_5.0 and E with change in the moisture content increase with the temperature rise (Fig. 6 and Table 4).
   4) The relations of σ_p, σ_2.5, σ_5.0 and E to the temperature and the moisture content in the range investigated are represented by the equation (3) and the parameters are given in Table 5.

   This report deals with the effect of blood glue mixed in water soluble phenol resin.
   The effect was judged from gluing strength and water resistance of plywood adhered by the glue in which phenol resin was extended with blood glue, and it was compared with those of other extenders such as casein glue, soybean glue, wheat glue and wood powder suspension.
   The results obtained from this experiment were as follows:
   1) There was no significant difference in the gluing strength between the mixture added in the proportion of 100 parts of the phenol resin to 10 parts of blood glue liquor in which the ratio of blood powder to water is 1 : 3 and the phenol resin only.
   2) It was recognized that there is no significant difference between the boiling water resistance of the blood glue added to the phenol resin and that of the blood glue only.
   3) As an extender of the phenol resin, it was recognized that the blood glue has the casein-like effect.