St-ptfUilx'r 10. 1922 



HARDWOOD RECORD 



27 



Testing Kiln Circulation with Chemical Smoke 



Since it is the air that removes the moisture from the surface of 

 lumber in a dry kiln, the movement of the air must be ample in all 

 parts of the kiln, or uneven drying will result. The drift of smoke 

 produced by some burning substance is often used as an indicator 

 for searching out zones of too rapid or sluggish circulation in kilns. 



This method is greatly facilitated by the use of the apparatus 

 shown here which was developed at the U. S. Forest Products 

 Laboratory, Madison, Wis. In this device, the use of which involves 

 no tire hazard, as in burning rope, punk, etc., in the kiln, the fumes 

 of hydrochloric acid are blown across ammonia; and an abundance 

 of harmless, visible fumes are produced. These fumes, being of 

 approximately atmospheric temperature, have little tendency to rise 

 or fall independent of air currents. 



Comparative Strength of Air-Dried and Kiln- 

 Dried Wood 



Some wood users claim that kiln-dried wood is brash and not 

 equal in strength to wood that is air-dried. Others advance figures 

 purporting to show that kiln-dried wood is much stronger than air- 

 dried. But some 150,000 comparative strength tests, made by the 

 Forest Products Laboratory, of the V. S. Forest Service, on kiln- 

 dried and air-dried specimens of 28 common species of wood show 

 that good kiln drying and good air drying have the same effect 

 upon the strength of hardwood. 



The belief that kiln drying produces stronger wood than air 

 drying is usually the result of failure to consider differences in 

 moisture content. The moisjture content of wood on leaving the 

 kiln is generally from 2 to 6 percent lower than that of thoroughly 

 air-dried stock. Since wood rapidly increases in strength with loss 

 of moisture, higher strength values may be obtained from kiln- 

 dried than from air-dried wood. Such a difference in strength has 

 no significance, since in use a piece of wood will come to practically 

 the same moisture condition whether it is kiln dried or air-dried. 



It must be emphasized that the appearance of the dried wood is 

 not a reliable criterion of the effect the drying process has had upon 

 its strength. The strength properties may be seriously injured 

 without visible damage to the wood. Also, it has been found that 

 the same kiln-drying process can not be applied with equal success 

 to all species. To insure uninjured kiln-dried material, a knowledge 

 of the correct kiln conditions to use with stock of a given species, 

 grade, and thickness, and a record showing that no more severe 

 treatment has been employed, are necessary. 



Tiemann Returns from Australian Service 



II. D. Tiemann, dry kiln expert of the U. S. Forest Scrvico and special 

 lecturer in forestry and wood utilization at the University of Wisconsin, 

 has returned from a ten months* trip in Australia and New Zealand. Mr. 

 Tiemann's sen'ices were loaned by the United States government at the 

 request of the Australian Forest Commission to advise them concerning the 

 kiln drying and utilization of native timber. In addition to advisory and 

 experimental work, Mr. Tiemann conducted a course of lectures on kiln 

 drying, which are to appear as a Victorian Government Bulletin. He 

 ■ifarted an agitation against forest fires and also delivered numerous 

 addresses and lectures in Melbourne. Perth, Christchurch. Wellington and 

 Auc-kland. .\n enthusiastic farewell reception was given Mr, Tiemann and 

 Mrs, Tiemann on the occasion of their departure at Melbourne. 



Bulletin on Air Collecting and Conveying 



The B. F. Sturtevant Co. of Hyde Park. Boston, Mass., has just issued 

 a new 72-page Engineering Bulletin on Pneumatic Collecting and Conveying. 



It contains S3 pages of pictures and diagrams, 17 pages of useful tables — 

 how to find the size of fans, the suction, volume, R.P.M. and horsepower 

 for any system, cubic feet of air handled per minute, size of pipe and ducts 

 used, and various other valuable tables. 



Data is also given on dust collecting from grinding and polishing 

 machines, tumbling barrels, sand blast machines, coal breakers, shoe 

 machinery and the removal of fumes, gases, etc. In addition, there are 

 parts on the conveying of pulverized coal, fibrous materials, coffee, ashes, 

 wool, wood chips, etc. It is a most comprehensive treatise on Pneumatic 

 Collecting and Conveying Systems. A copy will be sent on request. 



-^ 



LW^RK-^ 



PUf^AJHR; 



HUMIDITYl^RY KILN 



The kiln with a circulation you can understand 



[IGH 



And Shoe Lasts 



In all probability, the shoes you 

 wear are dependent, in a measure, 

 for their good appearance on a 

 Sturtevant Dry Kiln. 



The shoe last is kept inside the shoe 

 while it is being made so that when 

 the shoe is finally completed, it takes 

 the exact shape and mould of the 

 last inside. 



Should a last swell or shrink ever so 

 little, while the shoe is in the mak- 

 ing, the result would be an ill-fitting, 

 uncomfortable, poorly-shaped shoe. 



Good shoe-last manufacturers, there- 

 fore, dry their somewhat expensive, 

 clear, maple blocks in a Sturtevant 

 Kiln. 



Bulletin 282 is in reality a practical, 

 authoritative treatise on lumber 

 drying. 



Your copy is here tor the asking. 



HYDE PARK, 



BOSTON, MASS. 



688 



