Frequently Asked Questions about Foil Stamping Process

Foil stamping process can greatly enhance the added value of packaging products and is widely used in the production process of printing and packaging companies. To address some technical issues related to this process, we have compiled this Q&A based on interviews with experienced printing factories, hoping to provide references for packaging and printing enterprises.

1. Q: What is the difference between embossing on a raised box and embossing on a flat box?

   A: The distinction between embossing on a raised box and embossing on a flat box lies in the following: Generally, embossing a raised image can be applied to both large and small raised areas due to its high-speed embossing method. Flat embossing, on the other hand, is more sensitive and prone to printing defects as it is less effective at releasing air. Flat embossing is suitable for small-sized patterns, lines, and text, but it has a slower embossing speed.

2. Q: What is the difference between foil stamping on laminated board and foil stamping on white cardboard?

   A: The main difference lies in adhesion. The adhesion between the adhesive layer of electroplating and the material being stamped determines the result. Foil stamping on white cardboard produces better results than on laminated board due to the higher surface tension of white cardboard. Ordinary oil coatings or UV oil coatings are commonly used on white cardboard. Laminated board generally requires specialty printing inks such as JP series from Hanghua Chemical Co., Ltd or UV oil coatings. Since the surface of laminated board is smooth and dense, flat embossing is not effective in releasing air. It is best to use raised embossing methods in conjunction with a line-hot stamping machine.

3. Q: What should be considered when performing overprinting on foiled areas?

   A: It is important to avoid applying gloss coatings on foiled areas, as it may prevent the transfer of the adhesive layer. Before foiling, it is advisable to conduct test prints and conduct thorough research on the materials and characteristics of the coatings.

   (1) When overprinting after foil stamping, special attention should be given to the lack of affinity between electroplating and coatings. If possible, the foiled areas can be surface treated.

   (2) Using an aluminum with a surface tension of 4.0-4.6 * 10 - 2N/M and good adhesion to coatings is recommended.

4. Q: What issues should be considered when electroplating on UV coatings?

   A: Generally, there are fewer problems when using solvent-based or water-based coatings, but issues may arise with UV coatings. This is mainly related to the affinity between the coatings and the surface of the substrate.

   (1) Foil stamping on UV coatings may result in poor adhesion. To ensure proper adhesion, it is necessary to make sure that the surface tension of the electroplating is greater than that of the UV coatings.

   (2) If possible, the non-foiled areas can be left uncoated or foil stamped after UV curing.

   (3) It is recommended to conduct test prints first and then determine the foiling process and materials.

5. Q: What are the possible reasons and solutions for inaccurate registration during changing box printing?

   A: 

   (1) Paper deformation: Lowering the drying temperature during printing can help alleviate this issue (as high temperature can cause paper shrinkage).

   (2) Heating unevenness during foil stamping: For multiple foil stamping points on one stamping plate, careful control of temperature fluctuations of the plate can help address this issue.

   (3) Lack of consideration in plate making for scaling down foiled patterns, texts, or lines.

   (4) Issues in previous processes: Ensuring consistency with the front guide and side guides (distance from paper edge to finished line) can help address this problem.

In addition, factors such as ambient temperature variability, human factors, and equipment precision can also contribute to inaccurate foiling. Therefore, these factors should be taken into consideration during the production process.