22 NEW YORK STATE MUSEUM 



destructible by fire. For inside purposes, whenever it is necessary 

 to nail woodwork, the blocks are made porous by the addition of 

 sawdust during the process of manufacture. This is the variety 

 usually reported as terra cotta lumber. For foundation work a 

 special block is made with a salt glaze, rock finish face. 



The product as manufactured in this State is made by the stiff 

 mud process. Both clays and shales are used, either separately or 

 mixed, depending upon local conditions. While the clays of the 

 Hudson valley are not usually suitable for the manufacture of stiff 

 mud products, there are local beds, especially among the delta de- 

 posits, that can be employed for this purpose. Such deposits occur 

 near the mouth of the Mohawk river and are utilized for the manu- 

 facture of both fireproofing and common hollow brick. The cal- 

 careous clays of the western section of the State are also used, and 

 the shales of the extreme western section are especially adapted. 

 The soft plastic clays are prepared for manufacture by first passing 

 through a disintegrator, which is practically a pug mill, without the 

 addition of water. Coal screenings, sand and grog of crushed 

 burned brick may be added at this point. The mixture then goes 

 to a set of rolls, then to the pug mill, and finally to the machine. 

 The shales are usually pulverized in a dry pan, water is added and 

 the material then passed through a wet pan as a substitute for the 

 pug mill. While the horizontal auger machine is usually used in 

 the manufacture, the tile press is also employed. Drying is carried 

 on in steam, waste heat, or direct heat tunnels and also in a covered 

 pallet yard. The product is burned in round down-draft kilns using 

 bituminous coal. Burning requires about five days. The finished 

 product goes mostly to outside markets and generally on contract. 

 There were seven firms actively engaged in the manufacture of fire- 

 proofing during 1913 in this State. The production of fireproofing, 

 exclusive of common hollow brick, in the last four years has been 

 as follows: 1910, $256,820; 191 1, $229,627; 1912, $230,833; 1913, 

 $276,053. 



TERRA COTTA 



Terra cotta is manufactured in this State to a large extent, al- 

 though all the materials except some of the clays used in the glazes 

 are brought in from outside sources. At one time the Staten Island 

 clays were employed in a local plant. The value of the yearly out- 

 turn has recently exceeded $1,000,000, having been $1,113,322 in 

 1913 and $1,139,291 in 1912.- 



