Paper bag printing is widely used for product packaging in the healthcare, footwear, gift, pharmaceutical, and other fields. Currently, these widely used paper tote bags can be categorized into two types.

One type is ordinary paper bags for popular packaging. These bags are mostly produced using rotary printing and automated production lines. Kraft paper is often used, and the specifications and patterns are relatively rigid. Their advantage is high production efficiency and suitability for large-scale production. The other type is beautiful and exquisite packaging and shopping bags. These bags are generally printed on single sheets and rely on manual or semi-automatic production. Kraft paper, coated paper, and cardboard are commonly used as materials for processing. They are mostly used for packaging high-end goods, gift bags, and advertising bags for various commercial activities. Their characteristic is that they can be produced in any shape and size, but the process is complex and production efficiency is low. This article will focus specifically on this type of paper bag and discuss the production process of paper tote bags.

While the production process for paper handbags is complex due to functional or design requirements, the basic process can be summarized as follows:

1. Design

The design and production of paper bags is a key step in the entire production process. Most paper bags are an extension of product image and advertising strategies, so the materials, decorative techniques, and presentation are closely linked to the bag’s purpose and effectiveness. Kraft paper offers good toughness and strength, but a rougher surface. Cardboard offers good stiffness but poor toughness, and is generally coated for use as a paper bag. Coated paper has a certain toughness and can print rich colors, but its stiffness is inferior to cardboard. Kraft paper is often chosen for durability, while cardboard is often used when both color and stiffness are important. For vibrant patterns, coated paper is often preferred. To enhance the quality and class of paper handbags, designers have devoted considerable effort to post-printing surface decoration techniques. The flexible use of hot stamping, UV coating, varnishing, multi-color embossing, embossing, and flocking creates vibrant colors, a more three-dimensional effect, and a richer, more expressive look. Regardless of the finishing process used, designers should consider the economical use of paper materials and the rationality of the process design. For production and quality control, a complete and clear set of engineering drawings is essential during the design process. In most cases, the product will also require proofing. Proofing during design not only verifies the process, but also serves as a basis for customer approval and a production specimen.

2. Materials and Common Specifications

200g, 250g, and 300g white cardboard, 250g and 300g gray cardboard, 200g and 250g kraft paper

Common Specifications:

A. Oversized Tote Bag Size: 430mm (H)* 320mm (width) * 100mm (sides)

B. Large Tote Bag Dimensions: 390mm (height) * 270mm (width) * 80mm (sides)

C. Medium Tote Bag Dimensions: 330mm (height) * 250mm (width) * 80mm (sides)

D. Small Tote Bag Dimensions: 320mm (height) * 200mm (width) * 80mm (sides)

E. Extra Small Tote Bag Dimensions: 270mm (height) * 180mm (width) * 80mm (sides)

3. Printing

Because paper tote bags often serve as an extension of corporate image and product advertising strategies, their printing design differs from general printed materials. They often feature spot colors and full-page prints, using large amounts of ink and creating vibrant colors. Therefore, the printing process requirements differ from those of other products. Printers must pay special attention to ink balance and ensure proper equipment adjustment. Otherwise, ink banding and color shifts can occur. Some printing houses use less paper when printing invoices. When printing, it’s important to pay attention to the top and bottom, as well as the back and forth printing positions, to ensure the proper dimensions of the paper bag’s flap, top flap, and bottom. If the product requires post-printing lamination or other processing, it’s also important to minimize ink layer thickness, additives, and spray powder usage.

4. Lamination

Lamination, also known as post-print laminating, post-print gluing, or post-print laminating, involves covering the printed product with a 0.012-0.020mm thick transparent plastic film, creating a post-print finishing process that combines paper and plastic. It’s generally categorized as pre-coating or immediate coating. Depending on the film material used, glossy or matte film is used. With the use of water-based solvents, the environmental friendliness of lamination has been further enhanced. Non-kraft paper bags are often laminating because lamination increases color intensity, improves water and stain resistance, and generally enhances the paper’s physical properties, such as aging resistance, tear resistance, and puncture resistance. This improves the bag’s durability and strength, significantly increasing its load-bearing capacity. Matte film, in particular, creates a soft, luxurious, and comfortable feel.

The laminating process for paper bags requires careful attention: ① Select the appropriate laminating glue, especially for products with full-print metallic ink or those requiring subsequent embossing. ② Control the laminating speed and select the appropriate glue dosage based on the vehicle speed. ③ Products to be laminated must be completely dry after printing before laminating. Newly laminated products should also be allowed to sit for a period of time before rolling, cutting, or embossing. ④ If excessive powder is applied during printing, pre-lamination powder removal is essential. ⑤ Ensure the film’s corona effect is inspected thoroughly. Failure to adhere to these controls can easily lead to quality issues such as delamination, blistering, and pitting, and even lead to batch rejection.

5. Surface Treatment

Hot stamping, UV coating, and varnishing are widely used in the production of paper bags. They greatly satisfy consumers’ desire for exquisite and high-end paper bags. Key aspects of these processes must be carefully controlled during production.

Compared to gold printing, hot stamping offers a stronger metallic feel, better consistency, brighter colors, and a richer three-dimensional effect. A perfect hot stamping effect depends on the harmonious balance of temperature, pressure, and speed. During hot stamping, the following factors should be considered: ① the surface flatness of the product being stamped; ② the post-printing treatment of the product (such as lamination and oiling); ③ the hot stamping suitability of the anodized aluminum used; and ④ the condition of the stamping plate and press. Hot stamping is a complex process, and only by fully considering the influence of these factors can satisfactory results be achieved.

Surface varnishing processes primarily include UV varnishing and conventional varnishing. Varnishing can maintain a good gloss and improve surface wear resistance. In particular, UV varnishing and spot UV varnishing are used in paper bag processing to achieve thick, dense layers of printed material, a rich, moist luster, and a striking, visually striking print theme.

In addition, other printing finishing techniques such as embossing, colorful patterns, and flocking are also used to some extent in the paper bag production process. These techniques not only enhance the aesthetics and fashion of the paper bags, but also enhance the user’s lifestyle. Mastering the technical skills of these processes is crucial to further enhance the product’s appeal.

6. Die-cutting

Die-cutting, also known as “scribing,” involves combining a die-cutting blade and a creasing blade on a single template using a die-cutting machine. It is a crucial process in paper bag production. The quality of die-cutting directly impacts the quality of the paper bag’s shape and the efficiency of hand-pasting.

Key points to consider when die-cutting paper bags: ① Select the correct template. Since most paper bags have similar shapes and some sizes vary slightly, a first piece must be produced and compared to the engineering drawing to avoid using the wrong template. ② Control the working pressure. The die-cut edges must be free of burrs, with clear, dark lines for easy folding, but also free of flaking. Some paper bags may not show visible dark lines during die-cutting, but may crack during manual folding and gluing. Therefore, continuous trial folding and process inspection are essential during the die-cutting process. ③ Consider the paper’s characteristics. Paper folds easier along the grain direction, so mold pressure can be reduced. Paper folds more difficult perpendicular to the grain direction, so mold pressure can be increased locally. ④ Cardboard has poor toughness, so if it’s not coated, special attention should be paid to the die-cutting process.

7. Manual

The gluing process is the most unique step in paper bag production. Aside from the use of some semi-automatic equipment, it’s primarily manual labor, making it the least efficient step in the entire paper bag production process. Developed countries have a particularly high demand for exquisite paper bags, and since automated production lines are not feasible, this presents an export opportunity for many Chinese printing and packaging companies.

The gluing process for paper bags begins with careful first-piece process planning. ① Selecting the appropriate adhesive based on the paper bag material. Many paper bag factories, lacking process experience, often experience false gluing and cracking due to improper adhesive selection. Export paper bags must withstand temperatures as high as 50-60°C in shipping containers and as low as -20-30°C at the point of use. Adhesive aging must also be considered. Second, the construction, handle materials, and connection methods of paper bags vary widely, and we must explore appropriate manual processing methods based on the specific circumstances. Some require punching handle mounting holes before gluing, while others use hot melt adhesive to secure the handles during gluing. These manual gluing processes must be planned before mass production. Once the process is confirmed, we must strengthen detailed control during the gluing process to prevent contamination from excess glue and scratches on the paper bag surface during production. Of course, the process planning for the first piece of paper bag gluing before mass production can be referenced for process re-evaluation based on the process planning during proofing.

The finished paper bag is essentially finished after manual gluing. Some still require final steps—punching holes, stringing, and other processes—to complete the final packaging.

Through the above analysis and discussion of the paper bag production process, we know that exquisite and fashionable paper bags are ultimately completed through a series of complex processes. Any negligence in any process link can lead to production quality accidents. Rigorous process is essential to ensure product quality. Throughout the entire process, we must strengthen process evaluation management and the implementation of the first-article confirmation procedures before mass production of each process. At the same time, we must strictly track and control the production process. Any perfect process must rely on the strict implementation of process operating procedures to ensure its success, and the production of paper bags is no exception.