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Summary of instructions on practical color grading

  1. The comparison stones and the diamond to be graded should be Wei cleaned before each examination. Surface dirt and grease can affect the color.

  2. So that mix-ups can be avoided; the "examination stone" should be examined through the loupe prior to color grading, so that it can be recognize again at any time, especially if the grader is not working with his own comparison diamonds, or if the stone being graded is the same size as one 0 the master stones.

  3. A white background folded paper is necessary and the color-grading should be carried out in a neutral-colored environment.

  4. The choice of the correct daylight lamp is vital.

  5. The cleaned comparison stones should be laid table downwards at a interval of 1 cm from one another. The stone under test should be observed to the right and to the left of the comparison stones. When doubt occurs, the stone should be assigned to the lower grade.

  6. In order to reduce the surface luster the grader should breathe on the stones for color-grading.

  7. By moving the folded paper the incidence of light can be changed and distracting light reflections obviated.

  8. Attention should be paid to the make of the girdle, for it can strongly affect the color impact.

  9. Fancy-cut stones should be examined in several directions.

  10. Green- and brown-tinted hues should be graded in the Yellow Series
    according to their degree of saturation.

  11. Fluorescent properties should be tested and described.

Fluorescent diamonds Instruments for color-Grading