1. Squeeze and form the 8-g test sample into an oval-shaped mass. Roll this mass between the

fingers and the test board (fig. 15-38) with just enough pressure to roll the mass into a thread of uniform diameter throughout its length. The rate of rolling should be between 80 and 90 strokes a minute, considering a stroke to be one complete motion of the hand forward from and back to the starting point.

2. When the diameter of the thread has been reduced to 1/8 in., break the thread into six or eight pieces (fig. 15-39). Squeeze the pieces together between the thumbs and fingers of both hands into a uniform mass roughly oval in shape, and again roll out into a thread. Continue this alternate rolling to a thread 1/8 in. in diameter, breaking, combining together, and rerolling. Do this until the thread crumbles under the pressure required for rolling and the soil can no longer be rolled into a thread. The crumbling may occur when the diameter of the thread is still greater than 1/8 in. This is considered a satisfactory end point, provided the soil has previously been rolled into a 1/8-in. thread at least once.

3. Gather the portions of the crumbled soil together, place it in the moisture content can, and determine the water content from the difference in weight before and after you oven-dry it.

4. Repeat the process on at least two additional specimens. All three tests should agree within 1 percent. The plastic limit is simply the determined water content.