JOtHAL OF AGHCDLTTRAL RESEARCH 
DEPARTMENT OF AGRICULTURE 
Voe. V Washington, D. C., March 13, 1916 No. 24 
A NEW PENETRATION NEEDLE FOR USE IN TESTING 
BITUMINOUS MATERIALS 
By Charles S. Reeve, Chemist , and Fred P. Pritchard, Assistant Chemist , Office of 
Public Roads and Rural Engineering 
During the early period of the bituminous paving industry the asphaltic 
cement was usually tested by chewing a small piece and judging its con¬ 
sistency by its resistance to the teeth. With the development of the 
industry and specifications for work of this character it soon became 
evident that some more definite method of determining and defining* 
consistency must be evolved, and in 1889 H, C. Bowen, of Columbia 
University, first described 1 a machine for the purpose. This was fol¬ 
lowed some years later by the machines designed by A. W. Dow 2 and 
by Richardson and Forrest. 3 
All of these machines had for their basic principle the depth to which 
a No. 2 sewing needle would penetrate the material under certain speci¬ 
fied conditions of load, time, and temperature. Most, if not all, needle 
manufacturers produce No. 2 sewing needles, all makes of which are not 
necessarily of the same shape and size. Since it has, however, been gen¬ 
erally understood that the No. 2 needle manufactured by R. J. Roberts 
was that most often used for the selection of standard needles, the 
subcommittee of the American Society for Testing Materials which has 
the penetration test under investigation made the following recom¬ 
mendation in 1915: 4 
The needles for this test shall be R. J. Robert’s Parabola Sharps No. 2. They 
shall be carefully selected by the use of a hand glass, rejecting all that are manifestly 
of unusual shape or taper. Needles thus selected shall be compared with a standard 
1 Bowen, H. C. An apparatus for determining the relative degree of cohesion of a semi-liquid body. 
In School Mines Quart., v. io, no. 4, p. 297-302, 2 fig. 1889. 
2 Dow, A. W, The testing of bitumens for paving purposes. In Amer. Soc. Testing Materials, Proc. 
6th Ann. Meeting, 1903, v. 3, p. 354. 1903. 
3 Richardson, Clifford, and Forrest, C. N. The development of the penetrometer as used in the deter¬ 
mination of the consistency of semi-solid bitumens. In Amer. Soc. Testing Materials, Proc. 10th Ann, 
Meeting, 1907, v. 7, p. 626-631, 3 fig. 1907. Discussion, p. 632-637. 
* Report of sub-committee on penetration. In Amer. Soc. Testing Materials, Proc. 18th Ann. Meeting, 
1915. v. 15, pt. i,p. 353. 1915. 
Journal of Agricultural Research, Vol. V, No. 24 
Dept, of Agriculture, Washington, D. C. Mar. 13,1916 
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