Sour bins can lead to many problems. Be sure that your bin pH is between 6-7 for best worm health. Use strips to determine pH and then use crushed limestone to correct any problems. Many people compost without any need for pH test, but some prefer to test just to be sure. Also neat for class experiments. Contains 100 test strips and a color chart. To use; Mix a small amount of bedding material with water. Then put a drop of that water on the strip and look for color change. Compare the color to the chart to determine pH. For best accuracy compare color after about 20 seconds.