Definition
Paint black and white checkered paper is a special test substrate used to determine the covering power of coatings. It is typically made by printing or coating processes and has a regular alternating black and white checkered pattern on the surface, forming a high-contrast test background. Its core function is to provide a standardized and visual evaluation carrier for quantifying the covering ability of coatings, which is widely used in coating research and development, production quality control and related performance evaluation links.
Principle
Coating coverage refers to the ability of a paint to eliminate underlying pattern or color differences when applied evenly to the surface of a substrate. The test principle of black and white checkered paper is based on the visual or instrumental determination of optical contrast. The coating to be tested is evenly applied to the black and white lattice paper to form a wet film. As the paint dries into a film, the observer or inspection instrument evaluates how well the coating masks the black and white lattice pattern underneath. When the boundary of the black and white grid is completely unrecognizable, it is considered to have reached complete coverage. Coverage is usually expressed as the amount of paint required per unit area when fully covered, with lower values indicating the greater the coating's coverage capacity. This process involves the scattering, absorption, and interaction with the substrate of light in the coating.
Measurement method
Measurements are usually carried out in accordance with relevant national or international standards (such as GB/T 1726, ASTM D344, etc.). The main steps include: First, place the black and white checkered paper flat on a smooth glass plate. Subsequently, the paint is evenly scraped on the paper surface in one direction using a prescribed applicator (such as a wire rod applicator) to form a wet film. Place horizontally under standard temperature and humidity conditions to level and dry. After drying, under specified lighting conditions (usually northerly scattered natural light or standard light sources), the observer visually inspects or uses a reflectometer to determine whether the black and white grid pattern is visible. Repeat the test by adjusting the amount of coating or coating thickness until you find a critical point that completely covers the pattern. The final occlusion force value (X) can be calculated by the formula: X = (M/S) × 104, where M is the coating mass (grams) and S is the coating area (square centimeters).
Influencing factors
The accuracy and repeatability of test results are influenced by a variety of factors. The characteristics of the coating itself are key, including pigment type, particle size distribution, pigment volume concentration, and optical properties of the color distribution system. Coating process parameters, such as coating speed, pressure, and the accuracy of the applicator used, directly affect the uniformity of wet film thickness. The quality of black and white checkered paper, such as the contrast of black and white squares, the flatness of the paper, the absorption of liquids, and the surface gloss, will also interfere with observation and judgment. Environmental conditions, such as temperature, humidity during drying, and lighting conditions at the time of evaluation, need to be strictly controlled. The operator's observation angle and experience are also variables to consider.
Application:
Coating black and white checkered paper is mainly used in the coating industry and related material evaluation fields. In the coating manufacturing process, it is used for raw material inspection, formulation development and optimization, helping engineers compare the covering efficiency of different formulations. On the production line, it serves as a rapid quality control tool for monitoring the stability of the covering force of batch products. In addition, it is also used as a routine means to evaluate the basic properties of coatings in third-party testing institutions, scientific research institutes, and industrial fields involved in surface coating (such as building materials, furniture, printing inks, etc.). The test results provide basic data for product calibration, cost control (reducing paint consumption) and construction guidance.
Selection
Choosing the right coating black and white checkered paper requires comprehensive consideration of testing needs and standard compliance. First of all, the specific test standards to be followed should be clarified, which may have specific regulations on the size of the checkered paper, the ratio of black and white squares, the weight of the base paper and the surface treatment. Secondly, depending on the type of coating to be tested (e.g., water-based, solvent-based) and the expected coverage range, choose a lattice paper with appropriate liquid absorption and surface strength to avoid curling, penetration, or breakage of the paper during testing. For high-precision or arbitration testing, it is recommended to choose a product produced by a compliant manufacturer with stable batch quality and relevant performance descriptions. For daily quality control, regular products that meet the basic requirements can be selected. At the same time, it is necessary to ensure the match and accuracy of the test environment with auxiliary tools (such as applicators, balances).