608 



CALICO-PRINTING 



353 



tightening rack apparatus for 

 blanket; x, plaiting appara- 

 tus for printed cloth ; L, up- 

 right and batching apparatus 

 for grey cloth; M, driving 

 pullies and straps for batch- 

 ing and plaiting apparatus. 



The doctors used in clean- 

 ing off the superfluous colour 

 from the rollers, are gener- 

 ally thin blades of steel, of a 

 thickness varying from ^nd of 

 an inch to -ith of an inch, ac- 

 cording to the sort of engrav- 

 ing on the roller ; but some 

 colours, such as those con- 

 taining salts of copper, would 

 be too corrosive on a steel 

 doctor, and in this case doc- 

 tors of a composition like 

 brass are used. They are 

 filed to a bevelled edge, and 

 require to be retouched with 

 the file after printing from 

 10 to 30 pieces. The cylinder 

 or drum, in contact with 

 which revolve the copper 

 rollers, is wrapped round 

 with a cloth called ' lapping,' 

 which is generally a coarse 

 strong woollen cloth of pe- 

 culiar make, and is folded 

 tight on the cylinder about 

 J an inch thick. The blanket 

 is next put on and drawn 

 tight : this blanket is a very 

 important part of the ma- 

 chine ; it is a thick woollen 

 web, about 40 yards long, 

 and requires to be made with 

 great care, so as to be uni- 

 form in texture, thickness, 

 and elasticity. If the blan- 

 ket is uneven, it has the effect 

 of throwing the pattern into 

 confusion at the uneven 

 places. 



A good blanket will serve 

 to print 10,000 pieces, being 

 washed whenever loaded 

 with colour, and then is 

 suitable for covering the 

 tables of the block printer. 



In the year 1835 Messrs. 

 Macintosh and Co. patented 

 an India-rubber blanket, 

 which consists of several 

 thick cotton webs, cemented 

 together with dissolved 

 India-rubber. This blan- 

 ket is very useful and eco- 

 nomical for some purposes ; 

 the surface being very 

 smooth, great delicacy of 

 impression is obtained, and 

 when soiled it is not neces- 

 sary to remove it from thQ 



