Mineral Pigment Morphology Effects on Capillary Pressure and Vehicle Separation
Mineral pigment shape dictates coating pore diameter, where narrow platelet networks accelerate ink vehicle separation and induce print chalking.
TAPPI T 530
Ink Sizing
Aqueous liquid resistance of paper is evaluated by measuring the rate of change in reflectance as an acid ink penetrates the sheet. This test, designated as TAPPI T 530, is also known as the Hercules sizing test. The method utilizes a photometer to measure the time required for the reflectance of the paper’s top surface to drop to a specified percentage of its initial value.
This procedure applies to paper and paperboard where the degree of sizing affects writing and printing processes.
Penetration Rate
Acidic ink containing a green dye is applied to one side of the paper sample while the instrument monitors the opposite side. This test is highly sensitive to the internal sizing level of the paper and the presence of filler materials. A higher sizing level delays the penetration of the ink, which increases the measured time.
This data helps manufacturers adjust the dosage of internal sizing agents like alkyl ketene dimer.
Precision Control
Standardized reflectance drops of eighty percent or ninety percent are used to define the endpoint of the test. This setting ensures that the results are comparable across different testing facilities. Consistent measurements allow paper mills to verify that their product meets customer requirements.