﻿KILN DRYING HANDBOOK. 33 



done, this method will yield excellent results, but in any case a check 

 should be made at the end of the run, by cutting moisture sections 

 from the samples and comparing the actual moisture with the calcu- 

 lated moisture. Stress sections should also be cut from the samples. 

 Extra samples should be placed in the kiln, so that current stress and 

 moisture determinations may be made as desired. 



The use of end coatings on samples is imperative; coating the 

 ends of all of the stock in the kiln would be desirable in most kinds 

 of difficult drying, but is not considered economical except in un- 

 usual cases, such as in the drying of heavy vehicle parts, gunstock 

 blanks, and shoe-last blocks. The 213° pitch is recommended for 

 this work as well as for the samples. 



USE OF DRYING SCHEDULES. 



The drying schedules presented on the following pages are in- 

 tended to be used with kiln samples, the changes in temperature and 

 humidity being made as the moisture content of the samples passes 

 the various stages. All of the schedules are safe. It is possible to 

 obtain good results with faster drying, but the use of schedules more 

 severe than those recommended will require most careful judgment 

 on the part of the kiln operator. 



The schedules of widest application are the hardwood schedules, 

 originally intended for furniture stock, and the softwood schedules, 

 which provide for drying at higher temperatures. These two series 

 supplement each other and are numbered consecutively, No. 000 of 

 the softwood schedules being the most severe and No. 8 of the hard- 

 wood schedules being the mildest. 



Preliminary steaming has been mentioned for the relief of air- 

 drying stresses in partly dry stock. This treatment is also recom- 

 mended for green stock, not to relieve stresses, but to warm the stock 

 thoroughly before the drying operation begins. It is not necessary 

 to steam green stock so long as partly seasoned stock, 1 hour per inch 

 of thickness being sufficient. The temperature may be from 10 to 

 15° above the starting point of the schedule. 



All of the drying schedules are equally applicable to green and 

 to partially dried stock. The moisture of the stock as it enters the 

 kiln determines where to start on the schedule. Start on the point 

 of the schedule corresponding to that moisture content, disregarding 

 everything above that point, just as if the previous drying had been 

 done in the kiln in accordance with the upper part of the schedule. 



HARDWOOD SCHEDULES. 



The following instructions apply specifically to the hardwood 

 schedules in Table 2. These are intended to be used on all lumber 

 up to about 6/4 inches in thickness. Thicker stock can be dried by 

 using a schedule one number higher (milder) for each added inch 

 in thickness. It is intended that only one species and one thickness 

 be dried at a time. The wet-bulb temperature is included in the 

 schedule merely for the sake of convenience. Schedules 3 and 4 

 have been modified somewhat to conform to the other schedules in 

 the group. 



23241°— 23 3 



