CHAPTER XXIV 



Plaster 



Though less important than lime, plaster is 

 much used in building, especially for ceilings, 

 for chimneypieces and for joining bricks. It 

 is a white powder which is made into a paste 

 with water, being mixed in small quantities 

 as it is needed. The worker take a few 

 handfuls of the powder, which he dilutes in a 

 little water in his bucket, with the help of his 

 trowel. He takes the paste, spreads it on his 

 hand, uses it at once and then prepares some 

 more. Plaster cannot be mixed beforehand, 

 because it hardens very quickly, turns solid 

 and is then of no use. For it to be soft 

 enough it must be used as soon as it is pre- 

 pared. 



Plaster is made of a stone called gypsum, 

 which is always of the same nature, but which 

 varies considerably in appearance according 

 to the degree of its purity. Sometimes it is 

 a shapeless, whitish substance, more or less 



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