58 NEW VDKK STATH Ml'SKUM 



pore space when tamped than a sharp, angular sand, that a fine 

 grained sand will usually have a greater porosity than a coarse 

 grained, and that the minimum i)orosity can be obtained by a 

 mixture of rounded grains of several sizes. 



If a sand does not possess the desired permeability a mixture of 

 some other sand is often added to increase the j)ore space. The 

 coarser sands, since they have the larger pores, although their total 

 porosity may be less than a fine sand, li^ve usually the greater 

 permeability. 



The size of the particles is of importance in determining the use 

 of the sand. I""or a brass casting, for small iron castings or for any 

 work which requires delicate lines in the mold, a fine sand is very 

 essential, and sand for such work usually will pass almost com- 

 pletely through a sieve with loo meshes to the inch. Sands for 

 general iron casting are often much coarser, while the sands used 

 in making cores are very coarse, sometimes almost ranging into 

 gravels. 



Chemical analysis, although of less importance than a physical 

 examination, sometimes indicates the importance of detrimental 

 impurities such as calcium carbonate, an excess of iron oxids, etc. 

 Microscopic examination may also show certain minerals which 

 would be easily attacked by the hot metal, but ordinarily these are 

 of rare occurrence in molding sands. 



Distribution. As w^e have already seen, sands used for molding 

 purposes have a wide range in character and are therefore not 

 strictly limited to one type of occurrence. They occur both as 

 residual deposits, alluvial and beach sand of both Quaternary and 

 present age and as glacial deposits, all of which types are repre- 

 sented in this State. The most widely known molding sand in the 

 State and a sand recognized as a standard by foundrymen is the 

 Quaternary sands bordering the Hudson river and extensively 

 worked in Saratoga, Schenectady and Albany counties. Other 

 counties in the same belt producing molding sand at the present 

 time are Essex, Rensselaer, Greene, Dutchess, Orange and Wash- 

 ington. The sand throughout this area is very easily obtained, as 

 it lies in beds covered only by a thin coating of soil or sod. The 

 soil and sod over an area of a few rods is carefully stripped ofif 

 until the sand is reached. The sand is taken out and transported to 

 the railroad or river and either piled in large rectangular heaps or 

 placed directly in cars, or loaded into barges. The beds of good 

 sand vary from' 8 inches up to 8 feet in thickness, and a bed i foot 



