il_ 



HARDWOOD RECORD 



by means of the drying process. How does this compare with the 

 Russian style? Through the stewing in steam, under pressure, a 

 large amount of the water is driven out of the log; the higher the 

 pressure which is used, the more water is removed. Still, the pres- 

 sure should not be raised to more than fifteen pounds, for otherwise 

 the wood will get too dry. There is, therefore, in this method less 

 water left to be evaporated, following our drying. But something 

 else will happen when this steaming under pressure is used, that is, 

 the sap-cells of the wood are caused to burst, the pores are opened, 

 aud the largest part of the sap and foreign matter wliich is locked 

 up in the pores is driven out. 



As before stated, this steaming must be done with care, the pres- 

 sure being increased slowly. An increased pressure from the start 

 would destroy the structure of the wood. The main thing is to ob- 

 tain from the process a product that is soft enough for cutting, with 

 open pores, free from sap and containing less water than before 

 damping. 



A gentleman in the United States, who is thoroughly acquainted 

 with the veneer industry, told the writer that he has met with trouble 

 in attempting to dry maple veneer in a drying-machine with steam- 

 heated plates. The difficulty consisted in that from the interior of 

 the wood a sap came oozing, which stayed on the outside and formed a 

 sticky mass. He then tried to steam maple logs without pressure, 

 before the cutting. The result was that the drying in the plate- 

 dryer could be undertaken. What can we learn from this practical 

 example? In the first place, that though steaming in water a large, 

 even perhaps the largest part of the sap remains in the wood. In 

 the second place, how easily the sap can be driven out by contriving 

 a pressure in the cells inside, for there, as in this example, a wet 

 veneer strip is placed between two hot plates; where the temperature 

 is over 212 degrees, the water which is in the wood changes direct 

 into steam, and a pressure results, which drives out the sap. In the 

 third place we see from this example that even through steaming 

 without the least pressure, a part of the sap can be withdrawn. Still, 

 steaming without pressure carries with it one disadvantage that each 

 veneer man has experienced, namely — that the steaming does not work 

 evenly through the whole mass of the wood. 



But why is it that the removal of the sap is such an important 

 matter? Because, in the first place, as everybody knows, sugar sap, 

 resin, and similar substances, are extremely hostile to every glueing. 

 We cannot glue together maple veneer, when the exterior is covered 

 with a coat of sticky sap. In the second place, getting rid of the 

 sap plays undoubtedly a considerable part in producing waterproof 

 veneer, as we shall see farther on. 



As far as the cutting itself is concerned, that is done in Russia in 

 the same way as here, aud with machinery about the same ; still there 

 is a little difference. Sometimes a lathe with a movable knife is 

 used, that is, the knife moves forward and backward parallel with 

 the cutting edge. As we know, it is easier to cut wood when the 

 cutting edge moves in the direction toward the fibers of the wood. 

 Moreover, a smoother cut is obtained. In fact, this is a principle 

 which has come to be employed with almost all woodworking machines. 

 A veneer-slicer is known to be built on the same principle. Why 

 then should this principle not also be followed in a veneer lathe? 

 It is true that the machine gets more complicated, but it should be 

 remembered that such a machine need not be used for rough center 

 work stock, but rather for the best face veneer. Moreover, the 

 knife in such a lathe retains its sharpness quite a while. 



As to the drying and glueing, which then follows, the main dif- 

 ference consists in this, that according to the American method the 

 veneer is first dried and then glued, while the Russian process is just 

 the opposite. We shall see farther on what can happen in the two 

 instances. When the drying is done in the American way, the pores 

 in the wood are closed more or less, the surface becomes sometimes 

 somewhat case-hardened; at other times, glossy. When this veneer 

 passes through the glue-spreaders, the main part of the glue stays 

 on the surface. A small part crowds into the wood, as the moisture 

 of the glue opens the pores somewhat. What happens when the Rus- 

 sian method is followed? When the wet or only slightly dried veneer 

 goes through the glue-spreaders, the pores are open, and not alone 



this, but are also free from sap. The waterproof glue penetrates 

 into the pores and is absorbed by them. 



When this veneer is tlien placed under high pressure between steam 

 heated plates, the glue is pressed very strongly into the pores. In 

 this way even the larger i)ortion of the water which enters the wood 

 and glue turns into steam and goes off at the same time, carrying 

 with itself part of the glue, whereby the pores are filled even more. 

 Inasmuch as the external strata in three-ply are usually very thin, 

 it will be seen that these are almost entirely impregnated. 



It might be thought that this process works slowly and is expen- 

 sive. The fact is that it is slower than the American process, but 

 there is still another circumstance which should be taken into ac- 

 count. First, we see that while the American veneer contains per- 

 haps forty per cent to fifty per cent water before the drying, the 

 Russian contains not much more than half this amount. There is 

 therefore so much less water to be evaporated. If we, however, study 

 the principle of the drying itself closely, we find that two entirely 

 different principles come into play. Without further going into de- 

 tails on this matter, it might only be stated that according to the 

 principles employed in the American plan, a sufficiently large heat 

 is applied to the wood — such an amount as will cause the entering 

 water to pass into water vapor, then the air is heated sufficiently to 

 be able to take up this moisture and finally this moist air is gotten 

 rid of in a mechanical way by blowers, etc., which requires power. 

 Another principle for the drying is that to convert the water which 

 passes into the wood into steam direct. For this purpose no air is 

 needed. It is this principle that is employed in the Russian method. 



It would lead us entirely too far to show here in detail which 

 method takes more steam. One fact is while the Russian factories get 

 along with only about half the amount of steam that is employed by 

 the American ones, still they employ more steam at the time of steam- 

 ing the logs. Moreover, there are obtained in Europe at least two 

 glue presses with steam heated plates for the same prices as are paid 

 here for a blower dryer. Everything being normal, the capacity, with 

 glue presses of this kind, is about 180 cubic feet for ten hours, or 

 if we take for example 5/32 3-ply = 13,-500 square feet. If any 

 one should want to characterize in a short, perhaps somewhat exag- 

 gerated way, the difference between the American 3-ply and the 

 Russian waterproof 3-ply, this could be done, according to the writer 's 

 opinion, perhaps in the following manner: The American 3-ply con- 

 sists of three strata of wood glued together and the glue which is 

 between the strata has entered only to a small extent into the wood 

 itself, the pores of which are partly filled with dried or solidified sap, 

 hence the moisture is easily absorbed through the outer stratum and 

 dissolves the glue. The wood fibre or the skeleton itself of the wood 

 is, as will be noticed, not materially attacked by the moisture, but 

 it is the pores that imbibe the water, which causes the wood to swell, 

 destroying the glueing and breaking apart the wood itself. 



Russian 3-ply on the other hand consists of three strata of veneer 

 glued together, and the waterproof glue which is employed is to a 

 large extent driven into the pores of the wood which are empty and 

 free from foreign matter so that the whole face of the wood is 

 made waterproof. It is clear without further explanation that 3-pl.v 

 must become much more capable of withstanding the moisture. 



If the American veneer would be glued with waterproof glue one 

 would obtain, of course, a more or less waterproof product, but this 

 would still be not of the same kind as the Russian, because the wood 

 itself would continually be susceptible to moisture. 



It might still be said that every Russian veneer factory has a well- 

 equipped laboratory for the examination of glue, etc. The writer 

 has not noticed anything of the kind in the American factories. 



A Russian factory of middle size is built for about 210,000 cubic 

 feet of veneer per year. This is about a carload of twelve tons a 

 day. Of this there are only about 10,000 cubic feet unglued in dif- 

 ferent thicknesses. The material is divided about as follows : 



Cu. ft Sq. ft. 



4 mm. = r>/a2" = 50% of all glued veneer = 100.000 = 7. 500.000 



r, mm. = a/KZ" = 30% of all glued veneer = 60.000 = .■^,600.000 



6 mm. = 7/32" = 15% of all glued veneer = 30.000 = 1.500,000 



Thicker 5% of all glued veneer = 10.000= 3.30,000 



Unglued different thicknesses 10.000 = 600.000 



Total 210.000 13,530,000 



