Howard Mold Counting Chamber

The chamber is designed for use in determining mold counts in tomato products. The counting chamber is constructed entirely of glass. The center of the glass slide contains a 15 x 20 mm rectangle that is flanked by 0.1 mm shoulders on each side. These shoulders support a cover glass and provide a depth of 0.1 mm between the underside of the cover glass and the rectangle. Both the rectangle and the cover glass have optically plane surfaces. To facilitate calibration of the microscope, the rectangle features two engraved, parallel lines spaced 1.382 mm apart. The optional accessory eyepiece micrometer is ruled into squares, each of which is equal to 1/6 of the diameter of the eyepiece diaphragm opening. For mold counting, the microscope must give an area of 1.5 mm² (1.382 mm in diameter for circle) at a magnification of 90 to 125.