Page 659 



THE SMOOTH SHEET 

 Table 23. — Paper distortion 



7115 



Type of paper or material 



Cellulose acetate 



Buff paper, K. & E. No. 13322-M 



Chart paper (unmounted) 



Buff paper, K. & E. Duplex No. 141 (in sheets) 



White paper, Weil No. 72 



Buff paper, K. & E. Duplex No. 141 (in rolls).. 



White paper, K. & E. Paragon 



White paper, Whatman 



Tracing paper, K. & E. Ionic No. 197 H 



Tracing paper. Post No. 173 



Tracing paper, K. & E. Doric 



Tracing cloth, K. & E. No. 13303 



Percentage of distortion caused 

 by a change from 27 to 89 

 percent relative humidity 



7115. Seasoning Drawing Paper 



Smooth-sheet paper should be well seasoned in the clunate in which it is to be used 

 and for as long a period as practicable before the projection is drawn. Paper in tight 

 rolls, or in stacks or pUes, will not season. Each sheet should be laid out or hung up 

 separately where it will be completely exposed to the air on both sides for at least a few 

 days, if not weeks, before use. For best results the period of seasoning should embrace 

 a great variation of temperature and humidity. 



If a sheet cannot be seasoned by laying it flat, it should be hung from successive 

 edges and subsequently laid flat for several days before use. 



The contraction and expansion seems to be greater during the seasoning period 

 than subsequently. The paper seasons and settlesjlown so that less distortion may be 

 expected later. 



7116. Drawing Paper in Rolls 



Drawing paper in rolls is tightly rolled by the manufacturer and soon assumes a 

 set in this position. It must be unrolled with extreme care or it will have a tendency to 

 buckle or perhaps even crack. It is best to unroll it gradually over a period of several 

 days before trying to put it in a flat position. This is done by first loosening the outer 

 turns of the roll, until as much paper as is likely to be needed at the time has assumed a 

 diameter perhaps twice as large as the roll had originally. The next day it is expanded 

 again in diameter and so on, leaving it in the enlarged roll each time for a day, if possible, 

 until it can be cut off the roU and laid flat for seasoning. 



7117. Drawing Paper Requisitions 



All smooth-sheet paper requirements should be requested from the Washington 

 Office by ordinary letter, specifying the kind, grade, make, size, and quantity deshed. 



712. Smooth-Sheet Size 



The standard size of smooth sheets is 31 by 53 inches and they shall ordinarily 

 not exceed this size. It is sometimes impracticable to maintain this limit because of 



