July 10. 1922 



HARDWOOD RECORD 



29 



and coutmuous removal of any air accumulating within. This is all 

 important and must receive careful and competent attention. A kiln 

 with a sick heating system is very unsatisfactory and dangerous to its 

 contents. A good vacuum system of condensation removal will pay 

 for itself in short time and will return the condensate to the boilers 

 with minimum heat loss. 



Proper insulation of the steam supply lines is very desirable and 

 profitable. If steam lines must be run underground they should be 

 well insulated and run in concrete or tile conduits, supported on expan- 

 sion rollers, equipped with good expansion joints at regular intervals, 

 and suitable water drainage lines should be run under the conduits, 

 bedded in gravel or crushed rock. Condensation drains must be in- 

 stalle<l wherever necessary at low points. 



In tne above we have covered practically all of the essential features 

 of good dry kiln construction in such manner as may enable the inter- 

 ested party to understand and properly weigh the sales arguments of 

 the contractors and make an intelligent selection of the type of kiln 

 best suited to his requirements. The statements presented are based 

 on impartial observation and experience of many years with many 

 types of kilns, and there now remain for discussion only the various 

 methods of Humidity Control and Moisture Removal from the kiln. 



. Humidity Control and Moisture Removal 



This can be accomplished in different ways, more or less positive 

 and eflfective, and differs with the different kilns offered on the market, 

 although the principle remains the same. 



It has been stated that the moisture already in the kiln air controls 

 the amount of moisture which the air may take up in addition thereto. 

 To control the amount of moisture which remains continuously in the 

 kiln air, therefore, controls the rate of drying. The moisture in the 

 kiln air is expressed as its relative humidity, can be readily ascertained 

 by means of the hygrometer, and is prescribed in the various drying 

 schedules for the different species and thicknesses and their moisture 

 content. These schedules have been found satisfactory in service and 

 are reliable if properly applied. 



The natural method of controlling the proper percentage of vapor 

 saturation of the kiln air is by removing its surplus moisture only to 

 the point required and no more, so that this air when it shall again 

 become heated to the desired temperature in passing over the heater 

 coils will have the correct relative humidity as required by the sehediUe 

 before it enters the lumber pile. This is comparatively easy of ac- 

 complishment in some kilns and more difficult in others. 



To begin with, the kiln should be reasonably airtight in its con- 

 struction and doors to prevent undesirable outside interference by 

 infiltration of dry outside air, or too much leakage of the inside air 

 from the kiln. Next, it is necessary that the walls, floors and ceilings 

 shoidd be moisture-proof in their construction to prevent moisture 

 absorption during the early stages of drying, and the giving up of this 

 moisture (which may amount to a great deal) later on in the drying 

 period. Such conditions of leakage of kiln air and of moisture trans- 

 fer interfere seriously with good kiln drying, increase unnecessarily the 

 drying time, and likewise increase the drying cost. 



Properly constructed kilns of the Tiemanu Spray type are the most 

 positive in humidity control of the kiln air. The sprays, however, can 

 only he used during the forepart of the drying period and must later 

 be supplanted by condensers. 



Straight condensing kOns with properly located and constructed 

 condensers are likewise quite flexible in control of humidity in air- 

 tight rooms. 



The humidity control of moist air fan kilns is very easy of ac- 

 complishment and very certain, although in some cases the writer has 

 found it neces.sary to add moisture rather than subtract it, owing to 

 the accelerated leakage loss by the rapid movement of the air, which 

 addition is easily accomplished by a steam spray at tlie blower, and is 

 very positive and constant in result. 



With kilns employing gravity, or so-called natural ventilation for 

 their humidity regulation, the accomplishment is not quite so positive, 

 there being much interference by the varying condition of the outside 

 atmosphere, its changes in direction and intensity of wind pressure. 



Battery of Four 34 ft. Dry Kilns Used for Drying Cabinet Stock 



Greater Profits and 



Better Work with 

 Properly Dried Lumber 



Lumber for fine cabinet work' and good 

 furniture, seasoned in a Sturtevant High 

 Humidity Dry Kiln will not twist, warp 

 or crack; the glue will hold and the joints 

 will stay put. The green lumber can be 

 put in this Kiln straight from the saw, 

 eliminating delays and increasing your 

 profits. With the 



(§?5(urJevaril 

 High Humidity Dry Kiln 



T/ie Kiln with a circulation you can understand 



the moisture and temperature is kept exactly as 

 you want it, day after day. 



The moist, warm air is circulated and recirculated 

 reaching every part of the lumber; consequently 

 there is little or no wastage — another source of 



profit. 



Isn't it worth your while to write for the new cata- 

 log 282? It is full of data and information that 

 is of vital interest to you in your business. 



Alfi 



B. F. STURTEVANT COMPANY 



HYDE PARK, BOSTON, MASSACHUSETTS 



