Definition
Ink absorption tester is a special laboratory equipment used to determine the absorption performance of ink on paper, cardboard and other printing materials. This instrument quantifies the absorption of standard ink on the surface of the material within a specific time by simulating the ink transfer and penetration behavior during the printing process, and its measurement results are usually expressed as ink absorption values or absorption times. The instrument has important application value in the field of quality control of printing, packaging, papermaking and related materials, and its test methods often follow the national standard GB/T 12911, ISO 5637 and industry general technical specifications.
Principle
The working principle of the ink absorbency tester is based on the combination of fluid penetration and optical reflectance measurement. The instrument evenly applies the quantitative standard ink to the surface of the specimen, and the connecting material in the ink penetrates into the material under the action of capillaries, while the pigment stays on the surface to form an ink layer. Over time, the gloss or reflectance of the ink layer on the surface of the material changes due to the change in the absorption state of the ink. The instrument monitors the reflectance curve over time through the built-in optical sensor, and calculates the ink absorption performance parameters of the material according to the measurement time point or reflectance threshold specified in the standard. Its basic relationship can be expressed as:
R(t) = R0·e-kt
where R(t) is the reflectance at time t, R0is the initial reflectivity, and k is the constant associated with the absorption properties of the material.
Measurement method
The standard measurement process usually includes four stages: sample preparation, instrument calibration, test execution, and result analysis. First, the material is cut into standard-sized specimens and adjusted under constant temperature and humidity conditions. The standard ink is then applied evenly to the surface of the specimen using a dosing device, and the timing and optical measurement system is immediately activated. The instrument automatically records surface reflectance data at set intervals until the standard termination time is reached. Ultimately, the system calculates the ink absorption value based on the change in reflectance, which can be expressed as the percentage loss of reflectance over a specific period of time or the time it takes to reach a certain reflectivity. The test needs to be repeated many times, and the statistical valid results are taken as the final report data.
Influencing factors
The measurement of a material's ink absorption performance is influenced by a variety of factors. The fiber structure, porosity, sizing degree and surface coating characteristics of the material itself are the internal factors that determine its absorption performance. In terms of environmental conditions, laboratory temperature and relative humidity can affect ink viscosity and permeation rate, and standard testing usually requires 23±1°C and 50±2%RH conditions. Operating factors include ink coating thickness, coating uniformity, and timing accuracy, which need to be controlled through instrument calibration and standardized operations. In addition, reagent characteristics such as ink viscosity, pigment concentration, and binder composition can also have a direct impact on test results, so it is essential to use special test inks that comply with the standard.
Applications
Ink absorption tester is mainly used in the field of printability research and material quality control. In the paper industry, the instrument is used to evaluate paper printability and optimize sizing processes and coating formulations. Packaging material manufacturers predict the color reproduction and drying characteristics of printing by testing the ink absorption of corrugated cardboard, cardboard and other materials. Printing companies use the instrument data to adjust the ink formula and printing process parameters to reduce printing defects such as transmission printing and rubbing. In addition, in the field of special materials, such as decorative paper, label materials and printing plate bases, ink absorption testing is also a key means to evaluate the surface treatment effect.
Instrument selection considerations
When choosing an ink absorbency tester, it is necessary to comprehensively consider the measurement accuracy, functional configuration and applicable standards. The core parameters include reflectance measurement range, timing accuracy, coating control accuracy, and spectral adaptability of the optical system. The instrument should have automatic data acquisition and processing capabilities to support the test procedures specified by mainstream standards. In terms of structural design, a stable mechanical coating device, a temperature-controlled sample stage and a dust-proof optical system help ensure test repeatability. For R&D laboratories, models equipped with multi-angle measurement or multi-wavelength analysis functions can be considered; The quality control scenario pays more attention to ease of operation and testing speed. In addition, instrument calibration traceability, maintenance costs, and supplier technical support capabilities are also aspects that need to be evaluated during selection.