Definition
Coverage Jam is a specialized test substrate used to evaluate the coverage ability of coating materials such as coatings and inks. It is usually made of cardboard of a specific thickness, with contrasting areas of black and white printed on the surface, creating a stark difference in undertones. By evenly coating the material to be measured on the cardboard, its ability to mask the underlying black and white pattern is observed, thereby quantifying the material's masking performance. This tool plays an important role in quality control and R&D in the coatings, printing and related industries.
Principle
The testing principle of the masking force jam is based on the measurement of optical contrast. When the coating material is applied to the cardboard printed with black and white areas, light is reflected, absorbed, and scattered on the surface of the coating. If the coating coverage is insufficient, the black and white difference of the underlying layer will appear through the coating, resulting in the color difference between the coated area and the uncoated area. If the coverage is sufficient, the black and white background color is completely masked, presenting a uniform appearance. By measuring the reflectivity on the black and white areas after coating and calculating the contrast ratio, the masking effect of the material can be objectively evaluated. The formula for calculating the contrast ratio is:
CR = (RBlack / RWhite) × 100%
where CR is the contrast ratio, RBlackand RWhiteRepresents the reflectivity of the coating on the black and white areas, respectively. The higher the contrast ratio, the stronger the masking ability of the material.
Measurement method
Coverage jam paper measurement usually follows a standardized operating procedure. First, apply the paint or ink to be tested evenly onto the surface of the cardboard using a scraper or spraying equipment to ensure a consistent coating thickness and cover black and white areas. After the coating is completely dry, the reflectivity values of the coating on the black and white backgrounds are measured separately using a reflectance meter. Calculate the ratio based on the data obtained. Common test standards include ISO 6504-1, ASTM D2805, etc., which have specific regulations on the specifications, coating methods, drying conditions, and measuring instruments of the cardboard to ensure the repeatability and comparability of test results.
Influencing factors
The test results of the coverage jam are influenced by a variety of factors. The properties of coating materials, such as pigment concentration, particle size distribution, refractive index, and dispersion state, directly affect their scattering and absorption efficiency of light. Coating process parameters, including wet film thickness, drying speed, and uniformity, can also change the masking effect. In addition, the contrast of the base color, surface flatness and liquid absorption of the jam paper itself may interfere with the measurement. Environmental conditions such as lighting angle, temperature and humidity need to be controlled during visual evaluation or instrument measurement to reduce errors.
Application
Covering force cardboard is widely used in the production and research and development of coating materials. In the coatings industry, it is used to evaluate the covering performance of interior and exterior wall coatings, industrial paints and specialty coatings, and assist in formulation optimization and cost control. The printing ink industry uses this test to ensure the consistency and saturation of printed colors. In addition, in the fields of cosmetics, leather treatment agents and paper coatings, the coverage cardboard also provides a reference for product performance comparison. As a quality control tool, it helps manufacturers meet customer requirements and relevant industry standards.
Selection
Choosing the right coverage jam takes into account testing needs and standard compliance. The contrast of the base color of the cardboard should comply with the standard regulations, and the reflectance difference in the black and white area is usually required to be within a certain range to ensure the sensitivity of the test. The thickness, stiffness and surface treatment of the paper base should be able to resist deformation or penetration during the coating process. For specific materials, such as high-viscosity coatings or quick-drying inks, it may be necessary to use jammed paper with solvent resistance or fast-absorbing properties. Users should refer to applicable international, national, or industry standards to ensure that the jam specifications match the test method for reliable data.