Details:
Summary:
The drawdown type fineness-of-grind gages are coming into ever wider use for the evaluation of printing ink texture. It is, therefore, important that the fundamental principles involved be understood. Gages of this type are subject to two types of errors which affect their reproducibility. First, there are the errors arising from imperfect design and technique which can be reduced by careful study of the instruments. The reproducibility attainable by such work is limited, however, by the presence of a second type of error caused by the randomness of the distribution of the large particles through the ink. The mathematics of this source of error is treated and a limiting curve for the optimum precision of such instruments is obtained. This curve shows that exceeding, high errors may be encountered by the unwary technician. The particles found by this method of measurement are from the coarse ends of the particle size distribution curve for the ink under examination. The correlation of grind gage data with particle size distribution curves is worked out and discussed.