Five Reasons for Paper Bending and Warping

Introduction

Have you ever noticed that paper can sometimes bend or warp after being stored for a while? This can make it difficult to process and affect the final product’s quality. Don’t worry, though – this is often a normal occurrence. In this article, I’ll explain why paper bends and warps, and what might be causing it.

Why Does Paper Bend?

Did you know that paper is primarily made from wood fibers? These fibers are highly absorbent and can swell or shrink when exposed to changes in moisture. Temperature and humidity are key factors that can cause the moisture content in paper to fluctuate, leading the wood fibers to either expand or contract.

Each type of paper has an optimal moisture level that keeps it in good condition. If the moisture content changes due to environmental factors, bending and warping can occur. Different papers have different moisture ranges. For example, the moisture content of offset paper is typically between 4% and 6%, kraft paper usually has a moisture content of around 6% to 8%, coated paper ranges from 5% to 7%, and corrugated paper needs to maintain a moisture level between 6% and 10%. Single-sided coated whiteboard paper has the same moisture content as corrugated paper, while food packaging papers, such as whiteboard paper, typically have a moisture content of 6% to 8%.

Factors That Affect Paper Bending and Warping

The bending and warping of paper usually happen due to external forces or changes in moisture content. Here are the main causes:

Uneven Moisture Levels

 If the moisture content on the two sides of the paper is different, the side with less moisture will bend towards the side with more moisture.

Changes in Temperature and Humidity

Paper goes through various stages – from production to packaging to transportation. Exposure to different temperatures and humidity levels during these stages can cause the paper to bend or warp.

Packaging Type

Paper is often packaged either flat or in rolls. For example, kraft board tends to bend more near the core of the roll, especially thicker kraft papers. To fix this, it’s important to add moisture to the paper and press it flat for a while.

Uneven Pressure

If the paper is subjected to uneven pressure or if it shrinks unevenly, it can warp or bend in a way that isn’t uniform.

Moisture Loss

One of the main reasons paper warps is due to the loss of moisture. To prevent this, paper should be stored in moisture-proof packaging to maintain its quality and prevent deformation during later processing. Proper packaging helps improve production efficiency and reduce the likelihood of defects.

Conclusion

Now that you understand why paper bends and warps, you can take steps to prevent it. By controlling the storage environment’s temperature and humidity, you can minimize these issues. I hope this information is helpful! If you have any paper-related needs, feel free to reach out to us at Golden Paper for more advice.