BUILDING MATERIALS 167 



cow's hair, and water. Later improvements are known as 

 patent plasters. They differ largely from the old plaster 

 in that they contain the necessary hair or fiber and a per- 

 centage of plaster of Paris which results in a hard wall sur- 

 face. With the patent plaster the sand and the water are 

 the only ingredients which must be added. Portland cement 

 and natural cement plasters are mixed and tempered as in 

 cement surfacing work. Keene cement is plaster of Paris 

 which has been saturated with an alum solution, then burned 

 and reground. It is hard and very impervious to water. 



Substitutes. There are numerous commercial substitutes 

 for plaster and for lath and plaster which may be used on 

 temporary buildings or as an insulating course. They are 

 manufactured from wood and paper used in combination; 

 from wood fiber rolled into a thick sheet; from wood, 

 asphalt, and paper in combination; and from plaster and 

 paper in combination. Some are used as delivered; others 

 must be covered with paint or paper, while some must be 

 given a coat of regular plaster ii\ order to have a permanent 

 finish. There is little to be saved by the use of any of these 

 wall coverings. 



Paper. Paper is generally used as a protective and orna- 

 mental covering for plastered walls. It may be purchased 

 in a great variety of patterns and grades and comes 1 8 inches 

 in width and in single rolls of 23 lineal feet or double rolls 

 of 46 feet. It is stuck to the wall by means of a flour-and- 

 water paste. This paste is boiled to such a consistency 

 that it will spread in an even thin coat, but not run or drip 

 from the paper during the process of hanging. 



Paint. Paint is a liquid protective covering for exposed 

 surfaces. It is applied to all building materials, wood, steel, 

 brick, or stone. In composition it is a base, a vehicle, and 

 a solvent. 



Bases. Lead carbonate or white lead, zinc oxide or zinc 

 white, are the most common bases. Red lead, which is used 

 for barn paint, is lead oxide which has been burned. Barium 



