THE MANUFACTURE OF PAPER 



In most of the good grades of paper, such as ordinary 

 writing paper, the sizing is done, as we have seen, by 

 adding the sizing matter to the pulp. With some of 

 the finer grades of paper, however, the sizing is done 

 after the sheet of paper is formed, by passing it over 

 and under rollers through a vat containing sizing made 

 from horn, hide clippings, or some similar substance. 



When a very hard, smooth surface of paper is wanted, 

 there is an additional calendreing process besides the 

 first one just referred to, known as super-calendering. 

 The machine for doing this is a stack of rolls, a steel roll 

 alternating with one of solidified paper or cotton, the 

 stack containing from seven to fifteen of these rolls. 

 In passing through these the paper acquires a hard, 

 glossy finish. Considerable electricity is generated by 

 the action of the calender rolls; so much so, indeed, 

 that if not disposed of in some manner, it would inter- 

 fere seriously with the working of the machine, causing 

 the paper to stick, and gathering all manner of particles 

 of dust and bits of dirt from the surrounding air and 

 floors. To prevent this, ground-wires are usually laid 

 to carry off the current. 



PAPER FROM WOOD PULP 



Until the middle of the nineteenth century there was 

 very little change in the process of paper-making and 

 in the kind of material used. But about this time print- 

 ing-machinery began to make great changes and strides 

 of progress, and the demand for cheap paper became 

 imperative. The supply of rags could not meet the 



