Labels wrinkled or bulging? Printing curling? Key points for summer labels, check here!
Problems Caused by Changes in HumidityIn summer, the high environmental humidity can cause many troubles for adhesive label printing companies. If not addressed in time, it may lead to significant losses. Common issues with adhesive label usage due to humidity include the following:01 Curling During PrintingMost adhesive label printing uses UV ink. After drying under a UV lamp, the moisture in the adhesive label material is rapidly lost. Since the shrinkage rates of the label's face material and backing paper differ when losing water, it is easy for the material to curl. This phenomenon is especially noticeable when printing on thin film adhesive materials.This is because the face material of thin film adhesive labels is a film, while the backing paper is paper. During UV baking, the face material does not lose water, whereas the backing paper rapidly loses water and shrinks, causing the material to curl downward. If the workshop's environmental humidity is low, the backing paper cannot quickly absorb moisture from the surroundings, and the curling problem will not improve, seriously affecting production efficiency.If the workshop's humidity is controlled at a relatively suitable level, the material, although rapidly losing water under UV lamps, can quickly regain moisture from the environment. As a result, the material will not curl severely, and production efficiency will not be greatly affected. Therefore, it is very necessary to reasonably control workshop humidity in summer.02 Curling After Sheet CuttingMany adhesive label products need to be cut into individual sheets. Sometimes, we find that the labels curl quickly after being cut into sheets, making normal packaging impossible. In theory, the face material tension of the adhesive label should have been fully released after die-cutting and waste removal, so severe curling should not occur after cutting into sheets. So what causes this issue?
This phenomenon is often caused by a combination of improper material selection and poor environmental humidity control. There are many types of backing paper for self-adhesive materials, such as around 60g glassine paper, around 95g coated plastic paper, and around 120g cardboard. In principle, it is not recommended to use self-adhesive materials with backing paper under 80g for single-sheet label cutting. This is because thin backing paper is overly sensitive to environmental humidity, and when humidity fluctuates significantly, such paper can expand or contract with changes in humidity, causing severe curling of the self-adhesive material after die-cutting and waste removal.
To address this issue, the best solution is to choose backing paper with a higher grammage. The higher the weight of the backing paper, the less it is affected by environmental humidity, making it easier to ensure the flatness of labels after single-sheet cutting.
03
Variation in Raw Material Tension
In summer, we often encounter the problem of loose or tight rolls of raw materials, which usually occurs when materials are taken out for use after being stored for a period. In severe cases, they cannot even be used.
This is because the humidity in the air varies considerably in summer. After self-adhesive materials lose or absorb moisture, their tension changes, leading to loose or tight rolls. Some materials, especially thin-film self-adhesive materials, may have raised cores when used for the same reason.
Therefore, in summer, it is advisable to maintain minimal stock of self-adhesive materials and shorten storage periods, while strengthening warehouse management by following a "first-in, first-out" principle. Generally, materials will not undergo significant changes 7–10 days after arrival, and should not exceed 15 days.
Label Wrinkling and Bubbling
Summer is a high-incidence period for self-adhesive label faults, with wrinkling and bubbling being common issues for paper-based self-adhesive labels. So, what causes these problems?
01
Water loss during processing
During the processing of self-adhesive materials, the face paper of the self-adhesive product loses some moisture after being exposed to UV curing, resulting in very low water content in the finished labels. When end users use the labels immediately after opening the packaging, the labels absorb moisture from the air, swell, and expand, which causes wrinkling or bubbling in the expanded areas.
To prevent this problem, the best method is to reintroduce moisture to the self-adhesive materials during processing. This can be done by placing a humidifier at the roll-up station to humidify the backing paper. For companies with suitable conditions, it is recommended to install temperature and humidity control systems in the workshop to ensure the finished labels maintain normal moisture content.
02
Improper Storage Leads ToTypically, after printing, self-adhesive labels are packaged in plastic bags or wrapped with shrink film, effectively isolating them from the external environment. However, during the summer, frequent rain can cause a sudden increase in air humidity. If labels are applied at this time, they can easily absorb moisture from the air after being affixed, leading to wrinkles and bubbling.Therefore, it is important to pay attention when storing finished self-adhesive labels during the summer. It is advisable to open the packaging 24 hours before use, allowing the labels and the surfaces they will be applied to be kept in the same environment for 24 hours. This helps balance their humidity and ensures the quality of label application. This procedure is especially necessary when labeling corrugated boxes to guarantee effective labeling results.