74i5 NEW YOEK STATE MUSEUM 



STANDARD SAND 



Tlie question of a standard sand seems one of great importance, 

 for it has been found that sands looking alike and sifted through 

 the same sieves give results varying within rather wide limits. 



The material' that seems likely to give the best results is the 

 crushed quartz used in the manufacture of sandpaper. It is a 

 commercial product, made in large quantities and of standard 

 gradeSj and can be furnished of a fairly uniform quality. It is 

 clean and sharp, and, although the present price is somewhat 

 excessive (3 cents per pound), it is believed that it can be fur- 

 nished in quantity for about $5 per barrel of 300 pounds. As 

 it would be used for tests only, for purposes of comparison V\^ith 

 local sands, and with tests of different cements, not much of it 

 would be required. The price of the German standard sand is 

 about $1.25 per 112 pounds, but the article, being washed river 

 sand, is probably inferior to crushed quartz. Crushed granite 

 can be furnished at a somewhat less rate than quartz, and crushed 

 trap for about the same as granite, but no satisfactory estimate 

 has been obtained for either of these. The use of crushed quartz 

 is recommended by your committee, the degree of fineness to be 

 such that it will all pass a no. 20 sieve and be caught on a no. 30 

 sieve. Of the regular grade, from 15^ to 37^ of crushed quartz,, 

 no. 3 passes a no. 30 sieve, and none of it passes a no. 50 sieve. 

 As at present furnished, it would need resifting to bring it to 

 the standard size; but, if there were sufficient demand to warrant 

 it, it could undoubtedly be furnished of the size of grain required 

 at little, if any, extra expense. 



A bed of uniform, clean sand of the proper size of grain has 

 not been found, and it is believed that to wash, dry, and sift any 

 of the available sands would so greatly increase its cost that the 

 product would not be much cheaper than the crushed quartz, and 

 would be much inferior to it in sharpness and uniform hardness 

 of particles. 



MOLDS 



The molds furnished are usually of iron or brass, the price of 

 the former being $2, and of the latter $3 each. Wooden molds, 

 if well oiled to prevent their absorbing water, answer a good 

 purpose for temporary use, but speedily become unfit for accu- 

 rate work. A cheap, durable, accurate, and non-corrodible mold 

 is much to be desired. Molds are made for holding one, two or 

 more briquets. A common form is shoA\Ti in pi. 27. 



