Key insights in this article:
- Many recurring production defects, such as curling, waviness, cockling and dimensional deformation, are not caused by tension or temperature, but by moisture imbalance inside the substrate.
- Hygroscopic materials such as bio-based non-woven, carton, cotton, paper, wood and foils absorb and release moisture, which affects flatness, deformation, stability, strength and downstream processing.
- Moisture management is often overlooked in web-based production.
- This first article in the Fluid Application Series explains the root cause and why proper moisture control is essential for quality, consistency and OEE.
- The next articles will cover specific applications, including remoistening technology and static charge control.
Context and purpose of this article
In this opening article of our Fluid Application Series, we take a closer look at the real root cause behind some of the most common defects in high-speed web production: moisture imbalance inside the substrate. While operators often focus on mechanical settings, temperature adjustments or tension control, many of the recurring issues on the production floor like curling, waviness, cockling or dimensional deformation, can be traced back to moisture management within the product material.
This first blog sets the foundation: why moisture matters, how hygroscopic substrates behave, and why moisture control is still underestimated in many industrial processes. The next articles in the series will dive deeper into specific technologies, including remoistening systems and static charge control, and how they can be applied to improve quality, stabilize production, and increase OEE.
Production issues caused by substrate instability
You start a new production batch, and everything seems fine until curled edges, waviness (figure 1), or dimensional deformations appear. The previous batch of the same material ran without issues, so what has changed?
The first instinct of many operators is to adjust web tension, modify process temperatures, troubleshoot machine settings or blame it on the colleague. While this may bring temporary relief, it often leads to new issues such as another sort of deformation or even web breaks. The next batch may then behave differently again, forcing operators back to square one. This cycle not only reduces the overall equipment effectiveness (OEE) but also undermines team motivation. Only few things are more frustrating for skilled operators than a production line that stops more often than it runs.
Figure 1: Moisture imbalance can lead to substrate changes, such as waviness in paper, as shown in this example.
Why moisture imbalance leads to substrate deformation
In most cases, the underlying explanation of issues like curled edge and waviness is moisture management. While controlling the external environment humidity is certainly important, this blog focuses on the essential role of substrate moisture management.
This critical factor is often underestimated (both in literature and in practice) while in some other industries it is second nature. For example, textile manufactures control humidity to prevent fabric shrinkage and maintain fiber elasticity, while wood processors carefully balance moisture to keep panels flat and dimensionally stable during cutting and lamination. These industries largely understand that without controlled moisture, product quality and process efficiency suffer immediately. However, despite underlying reasons being known, a true and deep understanding is often lacking, leading to basic issues being overlooked.
In industries like non-wovens, effective moisture management continues to present challenges and room for optimization. With the rapid rise of new, recycled and/or bio-based materials, moisture behavior has become increasingly complex and important. These new fibers often have different absorption rates and surface properties, making consistent moisture control more challenging, but essential.
Moisture is especially important for hygroscopic materials such as bio-based non-woven, carton, cotton, paper, wood, wool, leather, and foils. Hygroscopic materials are substances that absorb and hold moisture from the air around them, while they can also release moisture very easily (Figure 2). They constantly try to reach a balance with their environment: taking up water when it’s too dry or releasing it when it’s too humid. This ongoing exchange means that the moisture directly influences physical properties such as length, weight, strength, shape, elasticity, and even electrical resistance. And with that being said, without proper regulation, process stability and product quality are compromised.
Because the properties of hygroscopic materials are sensitive to environmental conditions and thus to storage and process steps such as coating, finishing, printing, drying, embossing, and cooling, process control must include active moisture regulation.
Figure 2: Illustrative image showing how hygroscopic materials interact with their environment. The fibers continuously absorb and release moisture, adapting to surrounding humidity conditions.
Engineering approaches to moisture regulation in web processes
We know moisture matters. Contiweb has more than 40 years of experience in the field of advanced web solutions and has been active in remoistening since 2004. Our solution is direct remoistening, just before or after a critical process step, depending on your production line. This restores the moisture content of your substrate quickly and evenly to their optimal level. The result: well-known problems such as waviness, wrinkles, curling, shrinkage, cockling, jamming, swelling, caking or felting are effectively prevented, across all types of industries.
The importance of moisture management has long been recognized by Contiweb. Over the years, we have developed deep knowledge and practical experience in controlling and optimizing moisture content. Building on this expertise, Contiweb has created multiple variations of fluid application technology, each tailored to meet the demands of today’s high-speed, variable production environments. Whether it’s a printing line or packaging line, in paper, non-woven, textile or foil, Contiweb will precisely adjust the variables to the specific needs of each substrate, ensuring consistent quality, stability and productivity across a wide range of applications.
Besides moisture management, there are other advantages to maintain control over the process and substrate, and improve quality with a Fluid Applicator. This will be elaborated in the next blogs within this series:
• Elimination of static electricity.
• Application of other liquids, like silicone oil or anti-static for improved downstream handling.
• Other functionalities, like pre-moistening of sensitive substrates to stabilize performance prior to critical processes like drying, coating, finishing and embossing.
The outcome of using a well-controlled fluid applicator: no curled edges, no waviness, no wrinkling, no register or alignment issues, smooth finishing and no telescoping. With proper moisture management your substrates remain flat, the OEE remains high, and your operators remain motivated.
Request a substrate test in our demo Fluid Application Line
If you would like to determine how fluid application affects the behavior of your specific substrate, we invite you to have it tested in our demo fluid application line. During these tests, our (application) engineering team analyses moisture absorption, dimensional stability and downstream handling effects under controlled process conditions. The results provide practical guidance for process settings, and the expected improvements and feasibility within your production environment.
To discuss test options or technical requirements, you can contact Irene Eggink (Application Engineer) using the details provided alongside this article.
