34 



Hardwood Record — Veneer & Panel Section 



April 10, 1921 



Overcoming Walnut Seasoning Difficulties 



The advice recently given by Donald R. Brewster, specialist 

 in the seasoning of v^ood, to a furniture manufacturer, who was 

 having trouble with the splitting and checking of his walnut stock 

 after furniture was made up, appears to be of sufficient general 

 interest to warrant publication here. It is possible that other wood 

 users are having the same or somewhat similar difficulties, which 

 the information contained in Mr. Brewster's letter may help them 

 to correct. 



In order to more clearly understand Mr. Brewster's advice 

 it may be well first to read the question which this furniture manu- 

 facturer put. He said: 



"In connection with our furniture factory we operate a venti- 

 lated dry kiln. This holds two cars of lumber of approximately 

 5,000 feet per car. This kiln is equipped with spray, cold air ducts 

 and foul air vents and sufficient radiation to get temperature up 

 to about 185 degrees. We use a great deal of w^alnut and have 

 considerable trouble with checking and splitting after furniture 

 is made up. We think that possibly most of our trouble is from 

 drying too much and from some case-hardening. 



"Can you recommend a safe course to pursue with walnut, first 

 as to spray used, second, as to temperature, and thirdly as to w^hat 

 is the proper percentage of moisture walnut should contain w^hen 

 ready to take from the kiln? 



"Sometimes lumber seems to be dry enough, but on using the 

 various tests suggested, show case-hardening. Then if it is steamed 

 so that case-hardening is reduced, there seems too much moisture 

 content. 



"The writer has read many articles on kiln drying of lumber 

 in general, but none of them seem to say anything about the dry- 

 ing of w^alnut and that is what w^e are most interested in, as we 

 experience little or no trouble with the other kinds of lumber." 



Mr. Brewster's reply is as follows: 



"Considerable experience has shown me that it is alnriost im- 

 possible to work out the correct solution of a practical kiln dry- 

 ing problem without first making a careful study and diagnosis 

 on the ground, since many of the essentials of the problem can- 

 not be explained or brought out clearly by correspondence. For 

 this reason I cannot feel overly optimistic of being able to help 

 you very much in a letter but I shall be very glad to try. 



"I am familiar in a general w^ay with the type of kiln w^hich 

 you have. It is probably like most ventilated kilns — capable 

 of giving good results if the stock is fairly well air-dried and if 

 the kiln is tight and intelligently operated. 



"Your trouble with checking and splitting of walnut after the 

 furniture is made up is undoubtedly due to casehardening. The 

 tension in the fibers gradually breaks down the cohesion between 

 the cells, and fractures occur where the cells are w^eakest — along 

 the medullary rays. The way to prevent this with walnut is to 

 dry the wood with sufficiently mild conditions so that severe case- 

 hardening does not occur, in the first place, and then to steam 

 the stock judiciously at or near the end of the run to soften up 

 the outside and relieve any casehardening that is present, since 

 it is almost impossible to dry the wood in a ventilated kiln in a 

 reasonable length of time without some casehardening. 



"The exact kind and length of steaming treatment to use with 

 your stock w^ill depend upon its thickness and the degree of case- 

 hardening present. The thicker the stock, the longer the treat- 

 ment necessary and the earlier and more frequently should it 

 be applied. For best results in a steaming treatment, the air 

 should not be saturated but should have a humidity of from 75 to 

 80 per cent w^hich will cause the outside of the wood to absorb 

 enough moisture to accomplish the desired softening, without the 

 actual wetting of the wood and excessive absorption w^hich occur 

 with 100 per cent saturated steam. To guide you in giving the 

 right kind of steaming treatment you should have a good wet and 

 dry bulb recording thermometer so that you can tell the humidity 



accurately from without the kiln. With 4/4" stock you might try 

 a 3-hour steaming at 80 per cent humidity about 5 days before 

 the end of the run with a tenriperature of I 60 degrees. After this 

 treatment allow kiln to cool and dry dow^n gradually to drying 

 conditions w^ithout opening doors and with ventilators closed. 

 When stock has dried down to between 5 and 6 per cent, at w^hich 

 condition it is ready to remove, give another steaming of 6 hours 

 at 75 per cent humidity and 160 degrees. After steaming is com- 

 pleted turn off the steam sprays but leave the heating coils on for 

 the rest of the day. Then turn off coils and allow^ kiln to cool off 

 over night, after which it should be ready to remove the next morn- 

 ing in condition for immediate use w^ith moisture content w^ell 

 balanced at about 6 per cent and free from objectionable case- 

 hardening. With thicker stock steaming periods should be in- 

 creased in direct proportion to the thickness and the number of 

 days before the end of the run for the first treatment would also 

 be proportionately increased. 



"The standard schedule for black walnut, prepared by the 

 writer on the basis of a number of test runs while at the Madison 

 Forest Products Laboratory, is given in the following table: 

 Moisture Pet. Tempera- Pet. Rel. Approximate No. of days 



stock to 5 Pet. 



Average 



22 



20 



18 



15 



12 



6 



4 







"You will see that the initial conditions are dependent upon the 

 original moisture -content of your w^ood w^hich should always be 

 tested before the drying begins except in the case of stock which 

 has been on sticks a number of months and is thoroughly air dried. 

 If you control your spray and temperature so as to get approxi- 

 mately the above conditions at the different stages of the drying 

 and steam the stock as suggested above you should obtain satis- 

 factory results with your w^alnut. Aim to dry your stock to 5 per 

 cent. Then a slight absorption during the final steam will help 

 to balance the center and outside to a uniform condition of 6 per 

 cent, which is about right for your work if your factory is not kept 

 too dry. This will occur, since lumber dried to 5 percent w^ill ordi- 

 narily be about 4 per cent outside and 6 per cent in the center. ' 



Robbers broke into the office of the Cincinnati Veneer Com- 

 pany, 1285 West Sixth street, but were frightened away before 

 they got anything. 



J. B. Klinker, president of the Klinker Company, chair manu- 

 facturers, believes that a fire which destroyed his saw-mill plant 

 at Beach Fork, Athen County, Ohio, was of incendiary origin. 

 "The plants of our company at Rariden Scioto County, Ohio, 

 twice have been destroyed by mysterious fires w^ithin the last two 

 years," Mr. Klinker added. 



The Prestonia Manufacturing Company, Louisville, Ky., w^hich 

 has been manufacturing talking machine cabinets, has taken on 

 several side lines in mahogany, principally furniture specialties 

 such as library tables, sew^ing cabinets, davenport tables and other 

 small articles. 



The Mengel Co., Louisville, on April 5, announced reductions 

 of 1 5 per cent in wages to all office employes and officers, and 

 reduction of 1 8 per cent in all labor, this taking in seven plants 

 operation in various parts of the United States, including Louis- 

 ville, St. Louis, Jersey City, Winston Salem, Elkhart, Ind., Hick- 

 man, Ky.. and Mengelwood, Tenn. 



