Common Label Printing Issues: Why Does Paper Behavior Change?

In the printing process, we often encounter issues where the same type of paper labels that printed perfectly yesterday may deliver subpar results today. It often takes considerable adjustment of the equipment to ensure proper registration. Sometimes, paper labels left unused for a while tends to tear easily during printing. Has the paper labels changed? Why do such anomalies occur?

In printing production, paper labels is one of the consumables that is highly sensitive to environmental conditions. Composed of plant fibers and various additives, paper has a porous structure and strong hydrophilic properties. If the ambient temperature and humidity are not well controlled, the paper can deform, impacting the quality of the print. Therefore, maintaining appropriate environmental temperature and humidity is crucial for improving print quality and production efficiency.

How Temperature and Humidity Affect Paper Size

The reason temperature and humidity impact paper size lies in the porous and hydrophilic nature of paper fibers, which makes them highly sensitive to water. Even slight changes in environmental temperature and humidity can alter the moisture content of the paper. Typically, as the relative humidity increases, the paper’s moisture content also rises, causing the paper to expand, especially in the horizontal direction. Conversely, when the relative humidity decreases, the paper’s moisture content drops, causing the paper to shrink. The dimensional stability of paper is closely related to its suitability for printing operations and registration accuracy. This is particularly critical for multi-color printing products; significant changes in paper size can lead to registration errors, resulting in defective or waste products. Therefore, the impact of temperature and humidity changes on paper size is one of the most important factors affecting product quality. Additionally, changes in the paper’s moisture content can also alter other properties. For example, increased moisture content can reduce the paper’s tensile strength and surface strength, while decreased moisture content can make the paper brittle and more prone to static charges during printing.

Optimal Temperature and Humidity Conditions for Different Papers

Based on years of work experience and numerous experiments, we can summarize some key points: the ideal humidity for printing on aluminum foil paper is between 45% and 60%, while for storing coated paper, the optimal humidity is between 40% and 50%. However, these are not absolute values and should be adjusted while ensuring the stability of various raw material indicators. If raw materials have high or low moisture content upon delivery, they can also affect printing results, necessitating pre-drying or humidification.

In summary, controlling temperature and humidity in the printing workshop, especially humidity, is a crucial issue that cannot be ignored. Keeping workshop humidity stable within a reasonable range is essential to meet the requirements of the printing process. When choosing heating equipment, it is recommended to use direct heating methods in the workshop and install temperature and humidity meters at appropriate locations to monitor environmental conditions and make adjustments accordingly. It is important to note that after holidays or downtime, the workshop should be adjusted for humidity and temperature at least three hours before resuming work to ensure a smooth start to printing. The temperature and humidity requirements for printing different products are not entirely the same and must be adjusted based on the suitability of the paper being used. These adjustments require repeated verification and experimentation during the printing process. Ultimately, all printing data is closely linked to the accumulation and analysis of various process data.

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