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Increasing Kiln Capacity 





A large tight barrel mauufacturing concern has recently evolved 

 an idea which may be applicable to the hardwood and consuming 

 trades. It is oflfered merely as a suggestion, and with the knowl- 

 edge that there are some apparent weaknesses of the plan which 

 practice may show to constitute insurmountable obstacles. The 

 plan, in short, is to cut stock to size before, instead of after, kiln- 

 drying, so that the process of drying may be hastened and the 

 efficiency of the drier increased. 



In the case referred to, the barrel man has found it rather in- 

 convenient to put a lot of stock through the kiln and then after 

 tying up his drying equipment with this material for a couple of 

 weeks, to find that some of it has to be thrown out for use in 

 another direction, because it is not of the proper grade for the job 

 in hand; and also that by cutting to size and planing, a good 

 deal is taken off so that the material actually used is much less in 

 volume than that which occupied space in the dry-kiln. His idea 

 is to dry the staves only after sorting, cutting and planing, in 

 order to make the kiln do one hundred per cent of work. 



Some of the points which apply to the cooperage business do 

 not affect the ordinary factory using lumber, nor the hardwood 

 mill which does much cutting up. The main consideration — that 

 of making the kiln-space more effective — is one worth going into, 

 however, in view of the expense of operating a kiln, and the fact 

 that steam costs money. Certainly there is no use in wasting 

 drying efficiency if it can be profitably employed. 



The obvious objection to the plan of cutting to dimensions be- 

 fore drying is that if any defect is caused by checking or split- 

 ting, the piece is ruined for that particular use. To meet this 

 possibility by leaving sufficient margin would, in the first place, 

 require the stock to be reworked, and thus do away with any 

 advantage which had been gained; and in the second, would in- 

 crease the proportion of waste, which, in most plants, is great 

 enough as it is. 



It appears, therefore, that if the plan is used, the material would 

 have to be cut to the exact size required plus an allowance for 

 shrinkage. In order to prevent losses through checking or crack- 

 ing, more care would be required in drying. Perhaps this would 

 not be such a bad thing after all, for it is certain that the opera- 

 tion of most dry-kilns is not attended by what might be called 

 scientific exactness. Most users of lumber know about how long 

 it takes to dry lumber only in an approximate way. Usually no 

 exact figures are available, and of course allowance has to be 

 made for the condition of the wood at the time it is put into the 

 kiln. 



If the possibility of loss were present, and the superintendent 

 knew that his drying had to be done properly in order to prevent 

 damage, it is likely that greater care would be used in determining 

 the proper methods of drying, and in avoiding the harmful devel- 

 opments which at present mark much drying of lumTser. Nobody 

 ■wants to make the process any more difficult than it is, and it is 

 therefore certain that if the drying of dimension stock were 

 accompanied by extreme difficulty, this consideration alone would 

 be sufficient to cause the plan to be rejected. 



Undoubtedly, however, dressed stock dries more rapidly than 

 rough lumber. Planing it, before preparing it for use in the fac- 

 tory, removes the surface which has gradually hardened because 

 of air seasoning or from being kiln-dried at the mill, which makes 

 drying a slow process. If the surface had been gone over before 

 the final stay in the kiln, the warm air would get to all pores of 

 the wood more rapidly, and the moisture would be driven out in 

 a fraction of the time required under ordinary conditions. In the 

 cooperage plant referred to, experiments have shown that the 

 saving in time on this account amounts to fully one-third. 



Eight along the same line is the question of case-hardening. 

 This is usually the result of partial drying previous to being 

 placed in the dry-kiln. By reason of the first process, the 

 portion of the wood near the surface had dried out, and the in- 



—32— 



terior had remained as moist as before. Shoving it into the dry- 

 kiln in this condition, especially if the operator is not conserva- 

 tive in the matter of temperature, has a tendency to complete the 

 drying process, as far as the surface wood is concerned, leaving 

 the remainder as unseasoned as before, and making results ex- 

 tremely unsatisfactory. There seems to be good reason to believe 

 that if the lumber were dressed before being dried, and the sur- 

 face so opened as to make access to the pores of the wood cer- 

 tain, the chances of honey-combing or case-hardening would be 

 greatly lessened. 



There is a wood-worker in an Ohio valley city who uses beech. 

 Everybody who has ever handled this material knows how hard 

 it is to dry. In this case especially thick stock is used, and the 

 manufacturer was wont to fill the atmosphere with sulphuric ex- 

 halations because he was tied up more frequently than he would 

 have liked by reason of slow drying of his material. It may be 

 mentioned incidentally that his kiln was a little weak in con- 

 struction, though that is not the point. The problem of getting 

 that beech into shape in quicker time was discussed many times 

 by the manufacturer and his assistant, and no one seemed to be 

 able to get farther than the suggestion that a new kiln be installed. 

 This did not appear to be practicable, as far as the manufacturer 

 was concerned, so they had to find the answer at the other end of 

 the proposition. 



Finally a lumberman who had bad experience with beech sug- 

 gested that it be worked first and then dried. This, he pointed out, 

 would expose fresh .surfaces for the percolation of the heat, while 

 the fact that it dried slowly anyway made the danger of splitting 

 less prominent than it might have been with other woods or thin- 

 ner stock. The idea was seized with the eagerness with which the 

 proverbial drowning man catches a straw. It was tried, and has 

 succeeded. The manufacturer unloads his lumber from the car 

 right into the factor.y, as he usually buys it for immediate use, and 

 rips and saws it to the exact sizes required by the line of goods 

 he is putting out. Then, at first with fear and trembling, and 

 later with more confidence, he puts it into his dry-kiln. 



The latter is rather old and leaky, and consequently the tem- 

 perature is never excessive. The drying process is as slow, com- 

 paratively, as the most extreme might require. The consequence is 

 that there has been little trouble experienced from damaged stock 

 due to too rapid drying, and when the material has been in the 

 kiln the proper length of time, which is of course much less than 

 when it is dried without having been dressed previously, it is ready 

 to be finished and to go into place in the goods. In few eases 

 has it failed to give satisfaction. 



Absolute loss in case of checking in the kiln would be suffered 

 only in the case of small sizes, which could not be reworked into 

 something else; the larger pieces could be cut down to the smaller 

 dimensions used and thus the loss held to a minimum. But of 

 course if experience suggested that there would be a good deal of 

 splitting or checking, it would not lie wise to attempt the plan. 



There arc some consumers of lumber who carry no stocks on 

 their yards whatever. The tendency to leave the seasoning of the 

 stock to the lumberman, and to trust to the dry-kiln to cure what- 

 ever defects of this kind are still in evidence, is growing, and 

 will continue to exist as long as the consumer can get his lumber 

 with reasonable facility when he is in the market for it. The fact 

 that the smaller furniture factory, especially, dislikes to tie up 

 much capital in lumber, and buys for immediate consumption, 

 means, again, that greater reliance is placed on the dry-kiln than 

 in the past. This suggests two things: That the maximum effi- 

 ciency is required of the kiln, and that the greatest possible care 

 be given to the stock which goes into the drier. 



These two conditions seem to be met by the method of putting 

 the stock through the first stages of manufacture, at least, before 

 drying. The manufacturer who is in a hurry to use his stock can 

 thus do part of the work on the lumber without waiting for the 



