164 



The Philippine Journal of Science 



1914 



from the ground, mixed with water, and compressed in molds 

 by an animal-power Henry Martin machine. The clay is taken 

 from not less than half a meter below the surface to exclude loam 

 as much as possible, and water is added until a mud ball dropped 

 45 centimeters will flatten but not crack. No sand is used ex- 

 cept for the purpose of sanding the molds so that the green bricks 

 can be removed without diflficulty. The bricks are "hacked" 

 as soon as they are dry enough to withstand handling, and 

 finally they are burned in a kiln 45 meters long, 3 meters high, 

 and 2.5 meters wide. Wood fuel is used, and a white heat is 

 maintained for a continuous period of at least twelve hours. 



The appearance of the finished product is shown by bricks 1 

 and 2 in Plate I, fig. 1. No. 1 shows the appearance of the cut 

 surface which, owing to the extreme stickiness of the clay when 

 pugged to the consistency practiced at Iwahig, is deeply pitted 

 and ruptured. The sanded sides shown by brick 2 are fairly 

 smooth, but the white coral sand used for sanding the molds 

 gives the brick a very unpleasing appearance. Also, since the 

 sand is highly calcareous, it is converted into caustic lime which, 

 upon subsequent hydration, slakes and, in expanding, destroys 

 the original smoothness of the surfaces. Also, there is some 

 pitting and abrasion due to the slaking of nodules of lime 

 beneath the surface. It is suggested that the use of molding 

 sand might be avoided and the appearance of the brick improved 

 in consequence if the molds were merely dipped in water instead 

 of being sanded. 



The physical properties of bricks 1 and 2, which are given in 

 Table I, are characterized by excessive porosity, poor strength,, 

 and high absorption. 



Table I. — Pliysical properties of the brick manufactured at the Iwahig 



penal colony. 



Item, 



Dimensions in centimeters 



Weight in grams (dry) 



Apparent density (weight/ volume of brick).. 



Specific gravity 



Absorption of water in per cent _-. 



Modulus of rupture: 



Transverse strength in pounds 



Distance between supports in inches 



3PI/2bd2 - 



Crushing strength in pounds per square inch 



Brick. 



No. 1. 



No 



2. 



20.3X9.2X5.4 



20.5X9.7X5.5 



1.731 





1.883 



1.69 





1.71 



2.91 





2.94 



20.61 





20.22 



1.050 





970 



6.0 





6.0 



339 





274 



779 





701 



