Are the adhesive book pages wavy, warped, or uneven? Reasons and solutions for “uneven pages” in bound books and periodicals

After the wireless adhesive book is taken offline, sometimes the back of the book looks fine and doesn’t drop pages, but when you open it,Single or multiple inner pages “wave up”, “curl up”, and “become uneven” on their own——Like wrinkles that have been soaked and dried by water. This kind of “waves/warping of the book pages themselves” is not the same as “uneven edges on the back of the book” (2847) and “glue overflowing and dirtying the book pages” (2188): the problem with the shape of the back of the book is that the entire back of the book is bulging, which is the focus of this articleWaves on a single page of a bookPlease explain why it happened, how to determine it, and how to handle it.

1、 First, let’s answer directly: What is the wave on the page of a book and why is it classified as a separate category

The waves on the pages of the book refer to the undulations, warping, and unevenness of the bound inner pages, which feel like “waves and waves” when touched. It usuallyDoes not affect the opening of glue and the loss of pagesHowever, it affects the feel of browsing, alignment of graphics and text, and the appearance of the finished product, especially for hardcover/brochure/textbook. The root cause is almost always presentPaper moisture content+workshop temperature and humidity+book pressing and shapingThese three steps, not the glue itself, are ineffective.

2、 5 common triggers (by frequency of occurrence)

1. Paper moisture content does not match workshop humidity (most commonly)

Paper is a moisture absorbing material. Suggestions for the Book and Publication Workshop 15-26 ℃, relative humidity 45-65%(Subject to the requirements of the accompanying process environment). If the paper roll/table is left in a low humidity environment for too long and becomes dry, it will absorb moisture and rebound after being put on the machine, causing waves to form; On the contrary, high humidity paper will also warp when it enters the drying workshop. The “15-26 ℃ workshop” emphasized in the training is the baseline for humidity and temperature control.

2. Insufficient book pressing and shaping/wrong timing

After gluing, use a book press to compact and shape the book core. Insufficient pressure, or too early pressure (glue is still thin, paper is not yet formed), too late pressure (film has formed), the free stress of the paper is not suppressed, and it rebounds into waves after release. Thick books and picture books are more prominent.

3. Mixing of thick and thin paper/inconsistent paper

Mixing paper of different weights and thread directions in the same book results in inconsistent drying shrinkage rates, causing waves to appear when stacked together. When placing an order to change paper (such as changing paper and cover at a graphic store mentioned in 1901), it is easiest to step on.

4. Local excessive thickness of adhesive layer/uneven application of adhesive

The glue coating is too thick or the coating roller is in different states, causing local glue cooling shrinkage and pulling the paper out of the undulations. This is similar to “uneven adhesive layer” (2563 glue roller wear), but it is manifested on the pages of the book rather than the back.

5. Inconsistent thread direction (adjacent issue, only prompt)

The stretching and shrinking directions of paper with straight/horizontal threads are different (2212 has specifically discussed the impact of thread direction on fastness). This article is not repeated, only a reminder: when the waves are severe, first check whether the paper threads in the entire book are consistent, and then check the above four items.

3、 Key distinction: Don’t confuse these questions with each other

Simple note:The pages of the book read this article one by one, the back of the book was bulging and uneven, and the glue overflowed to read the overflowing glue.

4、 How to handle and prevent

1. Control the environmentStabilize the temperature and humidity of the paper and workshop within the recommended range (15-26 ℃, etc. according to the process card), and leave a time for temperature and humidity balance from the paper table to the machine to avoid sudden changes in dryness and wetness.
2. Press book shapingCheck the pressure and timing of book pressing, and extend the pressure holding of thick books/brochures appropriately; The state of the book pressing fixture is maintained.
3. Unified paper: Do not mix weight or threads with the same material; First, conduct sample verification for the paper replacement batch (refer to the 1901 replacement order process).
4. Check if the glue is evenly appliedWear of the coating roller and fluctuation of the glue level can cause local thick glue (2563), and maintenance should be carried out in a timely manner.
5. Light illness products that have been taken offlineAfter the environment stabilizes, the pressure on the book can be improved by reshaping it; Severe assessment of wave stress or rework.

5、 Relationship with Sunlife’s real business

Sunlife hot melt adhesive covers copperplate paper/adhesive paper/double adhesive paper/thin paper and other scenarios, corresponding to different models (292/296/295/298, 396/397/398, 391 flat, 39D test paper, 393/395 graphics, etc.). When customers provide feedback on-site that ‘the pages of the book are rippling’, priority should be given to the five end judgment of ‘moisture content – temperature and humidity – book pressing – paper mixing – even glue application’. Most of these issues are related to the matching of the process and environment, rather than the failure of the glue itself; Sunlife provides “Instructions for Use/Process Card” along with the goods, and regards “Workshop Temperature and Humidity Control+Process Training” as a support item to reduce such rework.

Explanation: The temperature, humidity, and adhesive layer thickness described in this article are general process points. Specific machine parameters are subject to Sunlife’s accompanying “Instructions/Process Card”; Different models have different opening times and wax quantities. Please refer to the actual model technical data for selection.