There are many methods for measuring the aqueous resistance of paper and paperboard. The many methods can be placed in categories depending on the way water hold-out is measured. One way of classifying tests could be direct versus indirect measurement. Another might be fixed time versus degree of penetration. Ink resistance by the Hercules method is best classified as a direct measurement test for the degree of penetration. Others classify it as a rate of penetration test. There is no one best test for measuring “sizing.” Test selection depends on end use and mill control needs. This method is especially suitable for use as a mill control sizing test to accurately detect changes in sizing level. It offers the sensitivity of the ink float test while providing reproducible results, shorter test times, and automatic end point determination.