Judging the quality of cultural paper requires considering five core parameters: basis weight, whiteness, smoothness, tensile strength, and environmental indicators. These parameters respectively affect the feel, visual appeal, printing effect, durability, and safety.
These indicators collectively constitute the "comprehensive quality" of the paper; a conclusion cannot be drawn based on a single parameter. For example, high basis weight ≠ high quality. If whiteness exceeds standards or environmental standards are not met, it may actually harm the eyes or endanger health. Here are specific methods for judging quality:
Basis Weight (g/m²): Determines thickness and stiffness; it is the "basic threshold."
Function: Reflects the weight per unit area of the paper, directly affecting thickness, stiffness, and the feel of turning pages.
High-Quality Standards: Daily Printing/Writing: 70–80 g/m², 80 g is the "golden basis weight," preventing bleed-through during double-sided printing.
Color Printing/Brochures: 100–157 g/m², thick and textured, enhancing visual quality.
Cover/Card: 200g/m² or higher, such as 250g coated paper for a stiff and less prone-to-bending cover.
Avoidance Tip: Too low a grammage (<60g) makes it prone to ink bleed-through and tearing; too high a grammage (>300g) may exceed the printer's capacity.
Whiteness (%): Affects visual comfort; too high can harm the eyes.
Function: Refers to the paper's ability to reflect light. Too high a whiteness is glaring, while too low a whiteness makes it appear dull.
Quality Standard:
For everyday use, a whiteness of 80%–88% is recommended for its gentleness and eye protection, meeting the requirements of GB/T 30130-2023 for paper used by primary and secondary school students.
High whiteness paper (≥93%) is suitable for advertising, brochures, and other applications requiring vibrant colors, but is not suitable for prolonged reading.
Avoidance Tip: Paper with a whiteness >90% often contains a large amount of fluorescent whitening agents, which can easily cause visual fatigue with long-term use and may even affect children's visual development.
Smoothness (seconds): Determines print clarity and is key to "printability".
Function: Measures the smoothness of the paper surface, directly affecting the uniformity of ink transfer.
Quality Standard: Measured using the Bekk method; the longer the time, the higher the smoothness.
High-quality cultural paper typically has a smoothness >100 seconds, achieving clear dots and vibrant colors in printing.
Impact: High smoothness: Clear images and text, uniform ink color, and good gloss.
Low smoothness: Prone to problems such as blurry ink marks, missing dots, and uneven printing.
