How to Avoid Costly Print Mistakes on Custom Printed Plastic Bags

You’ve just received your printed samples, and something doesn’t look quite right. You inspect the print quality closely, trying to figure out what went wrong.

The custom printed plastic bags look clean and professional, and the colors of the logo of printing are perfectly aligned. But the custom art prints on the very same bag are a different story. Fine details look blurry, the colors appear dull, and the finished result is far from your approved artwork.

The challenge is that custom printed plastic bags often carry both a logo of printing and custom art prints. These two types of artwork have very different production requirements. Many buyers treat them as ordinary graphics and overlook the differences, which can lead to repeated sampling, production rework, and unexpected costs.

1. Logo of Printing vs. Custom Art Prints: Different Requirements

A brand logo typically uses one to three spot colors, with single-color printing or two-color overprinting. This makes registration relatively straightforward.

An artistic design with gradients, shadows, and highlights is much more complicated. It needs to be separated into multiple colors, with a separate printing plate for each ink color.

Under China's national standard GB 7707 for gravure decorative printing, the allowable registration deviation is no more than 0.5 mm for major areas and 0.8 mm for secondary areas. In practice, the industry typically aims for a registration tolerance of around 0.2 mm.

Lines thinner than 0.4 mm are generally unsuitable for multi-color overprinting and are better printed in a single color. Fine lines that look perfectly clear on a computer screen may not reproduce accurately on plastic film.

Before submitting your artwork, make sure to enlarge or simplify overly thin lines and small text. If certain details must be retained, consider converting them to single-color spot printing.

2. White Ink and Color Performance on Plastic Film

When colored inks are printed directly onto transparent or translucent plastic film, light passes through the material and reduces color saturation. As a result, the finished artwork may look dull or grayish.

For vibrant custom art prints, a layer of white ink is usually applied first, followed by the colored inks. The coverage and consistency of this white ink layer directly affect how the final colors appear.

However, white ink coverage has its limitations. If too much ink is applied around the bag opening or sealing edges, it may peel or lose color during heat sealing. Excessive ink buildup can also weaken the seal.

For this reason, white ink is generally not applied all the way to the edges. Slightly lighter colors along the finished edges are often an intentional part of the production process.

When placing an order, specify the exact white ink coverage areas in writing. Avoid vague descriptions or short notes that could be interpreted differently by you and your supplier.

3. Plan Artwork Around the Folding and Sealing Areas

Bag manufacturing involves folding. Areas that are folded inward along the sides cannot display the full design once the bag is finished. Likewise, artwork near heat-sealing lines may be compressed during sealing, leaving visible marks.

Many buyers arrange their artwork directly on a finished-bag mockup. Although the design may look perfectly centered on screen, its position can shift during mass production.

This happens because the production team lays out the artwork on flat, unfolded plastic film, not on the finished, folded bag.

Ask your supplier for the flat dieline template and arrange all graphics within the unfolded layout. Keep key design elements away from the folding areas and heat-sealing lines. Move important artwork slightly inward to avoid distortion or cropping.

4. How Printing Plate Costs Affect Your Budget

Printing plate costs are calculated based on the number of colors, not the complexity of the artwork.

No matter how detailed a design is, a fixed number of colors means a fixed number of printing plates. Conversely, even a simple design can require more plates if it uses many different colors.

For small orders, the cost of printing plates is spread across fewer bags, making the unit price increase more noticeable. When comparing quotes for bags of the same size and material, differences in the number of printing plates are often a major reason for price variations.

Use a Pantone color chart to count the colors in your artwork rather than relying on how they appear on your screen.

Also, confirm whether the quotation includes the following:

• Printing plate charges.

• Additional plate costs for the white ink layer.

• Sampling fees and the supplier's sampling policy.

Clarifying these costs before placing your order can help prevent misunderstandings and unexpected expenses later.

5. Compliance Requirements for Plastic Packaging

For food-contact packaging, make sure the inks and plastic films comply with China's GB 4806 series of food safety standards before purchasing.

Export orders must also meet the regulatory requirements of their destination markets.

For shipments to the EU, check the relevant REACH requirements, including applicable SVHC (Substances of Very High Concern) restrictions, and obtain material composition information for both the film and printing inks.

For packaging used with children's products, heavy metal migration levels must meet the limits specified in EN 71-3.

Plastic shopping bags exported to the EU are also subject to thickness-related regulations. Bags with a wall thickness below 50 microns are classified as lightweight plastic bags and may be subject to restrictions or charges in certain regions. Ultra-lightweight plastic bags below 15 microns are permitted only in specific circumstances.

Always verify the applicable regulations before production and shipment. Never assume that your bags can be exported without additional compliance checks.

6. Check These Details Before Mass Production

Once you have confirmed the artwork, number of colors, white ink coverage, and print-safe areas, you can anticipate most of the final appearance of your custom printed plastic bags.

The remaining variations mainly come from the raw film material and the actual operating conditions of the printing equipment.

These factors can only be properly evaluated using physical samples. Photos alone cannot accurately reproduce the true colors and finish of the printed bags.

Our factory has extensive experience producing this type of packaging, including designs that combine brand logos with artistic graphics. We have accumulated a wide range of physical samples featuring different combinations of logo printing and custom art prints.

If you need real samples for reference, feel free to contact us.

FAQ

Q1: If I change the position of my logo but keep the original artwork, do I need new printing plates?

A: Printing plates record the fixed positions of the graphics. If you change the position of your logo, new plates will generally be required.

If the logo size and position remain exactly the same and you only replace the artistic design, you may be able to reuse the original logo plates and make new plates only for the updated artwork.

Q2: Are areas around the handle holes suitable for detailed custom art prints?

A: Not really. The punching process pulls and stretches the plastic film, which can distort the artwork or break fine lines around the holes.

It is better to place simple logos or solid-color blocks in these areas and keep detailed artwork away from the holes.

Q3: Does the same artwork need color adjustments when printed on matte and glossy plastic bags?

A: Yes, in many cases. Glossy film generally produces more saturated colors, while matte film absorbs or diffuses some of the color, making the finished design appear lighter.

We recommend producing separate samples on both finishes before placing your order. You can then compare the results and adjust the color intensity of the artwork for the matte version if necessary.