129 



cloth, the cloth to be kept away from them by means of 

 a wire screen; or they may be stored in a moist box or 

 closet. 



25. Care should be taken to keep the needle clean, as 

 the collection of cement on the sides of the needle retards 

 the penetration, while cement on the point reduces tne 

 area and tends to increase the penetration. 



26. The determination of the time of setting is only 

 approximate, being materially affected by the temperature 

 of the mixing water, the temperature and humidity of 

 the air during the test, the percentage of water used, and 

 the amount of molding the paste receives. 



Standard Sand. 



27. For the present, the Committee recommends the 

 natural sand from Ottawa, 111., screened to pass a sieve 

 having 20 meshes per linear inch and retained on a sieve 

 having 30 meshes per linear inch; the wires to have diam- 

 eters of 0.0165 and 0.0112 in., respectively, i. e., half the 

 width of the opening in each case. Sand having passed the 

 No. 20 sieve shall be considered standard when not more 

 than 1 per cent passes a No. 30 sieve after one minute 

 continuous sifting of a 500-gram sample. 



28. The Sandusky Portland Cement Company, of San- 

 dusky, Ohio, has agreed to undertake the preparation of 

 this sand and to furnish it at a price only sufficient to 

 cover the actual cost of preparation. 



Form of Briquette. 



29. While the form of the briquette recommended by a 

 former Committee of the Society is not wholly satisfac- 

 tory, this Committee is not prepared to suggest any 

 change, other than rounding off the corners by curves of 

 \z-\n. radius. 



Molds. 



30. The molds should be made of brass, bronze or some 

 equally non-corrodible material, having sufficient metal in 

 the sides to prevent spreading during molding. 



31. Gang molds, which permit molding a number of 

 briquettes at one time, are preferred by many to single 

 molds; since the greater quantity of mortar that c:m be 

 mixed tends to produce greater uniformity in the results. 

 The type shown in Fig. 4 is recommended. 



32. The molds should be wiped with an oily cloth before 

 using. 



