The Laundry. ^yy 



jecting edges of the segments. As the cloth dries, the projections of 

 adjacent fibres interlock, drawing the fibres closer together. If the 

 cloth is dried slowly the interlocking is slight. If the cloth is rubbed 

 briskly while wet, or if a hot iron is used, the interlocking of the fibres 

 is increased and the shrinkage is correspondingly greater. The use of 

 strong soap on woolen goods 

 greatl}^ increases the amount of py 



shrinkage, for the alkali of the 



soap acts chemically upon the 



^^ 





m 



woolen fibre and softens it, caus- tlkA||w| 



ing the toothed edges to become ^^'^^V |iy- 

 more prominent. A marked in- 

 terlocking of fibres takes place, Yi^.zz.— Woolen fhres. 

 causing the characteristic de- 

 crease in the size of a garment, with the attendant thickening of the 

 fibre and the board-like condition of badly washed wool. 



Action of alkalis on wool. Strong solutions of alkali, as lye or washing 

 soda, have a softening efTect on wool, and if allowed to act upon it for 

 any length of time, reduce it to a soapy-like liquid. 



Dilute solutions of borax, or a mild soap, if not much hotter than 

 blood heat, have only a slightly injurious action on wool. A good soap 

 is the least injurious form in which to use an alkali in cleansing 

 woolen fabrics. 



Action of acids on wool. Dilute acid does not affect wool materials, 

 but strong mineral acids will decompose them. In no case is the action 

 of acids on wool as destructive as on cotton. Dilute acid may be dried 

 on wool with no noticeable weakening of the fibre. 



Comparative action of acids and alkalis on cotton and wool. A graphic 

 illustration of the comparative difference between the action of acids 

 and alkalis on wool on the one hand, and cotton and linen on the other, 

 is furnished in an experiment which may be performed to determine 

 whether a fabric is all wool or part wool and part cotton: — 



Saturate a piece of the cloth to be tested in dilute sulphuric acid. 

 Dry it without washing. Rub it briskly between the hands. If cotton 

 is present it will fall out in the form of a grayish white powder. Or, 

 weigh a small sample of material and boil it for four or five minutes in 

 a 4% solution of caustic soda (lye). Dry and weigh it again. This 

 will show how much of the material is wool, as the wool will have, 

 been left behind in the caustic soda solution. 



III. Silk. Silk is the most delicate of all the fabrics and stands half 

 way between cotton and wool m its reaction toward both ^.cids p,nd aik^li§. 



