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During the flexo printing process, the main factor affecting the gloss of printed products like fast food paper bags, takeout paper bags, and bread paper bags is the smoothness of the ink film. This is determined by the properties and amount of the binder. The ink used in flexo printing machines should contain evenly dispersed fine pigments, possess sufficient viscosity, and dry quickly to prevent excessive penetration of the binder into the pores of paper bags like tea and sugar paper bags, nut paper bags, and fruit paper bags. Furthermore, the ink should have good flowability to form a smooth ink film after printing.

Flexo Press for Snack Cookie Paper Bag

Ink Film Thickness

After the paper has absorbed the ink binder to its full potential, the remaining binder remains in the ink film, effectively improving the gloss of printed products such as coffee bean paper bags, milk tea packaging paper bags, and wedding candy paper bags. The thicker the film, the more binder remains, which helps improve the gloss of paper bags such as baked food paper bags, hamburger paper bags, and fried chicken paper bags. Gloss increases with increasing ink film thickness. Even with the same ink, the gloss of bags made from different papers varies depending on the thickness of the ink film.

Flexo Printer for Dog Food Paper Bag

High Gloss Coated Paper

When the ink film on high-gloss coated paper is thin, the glossiness of bags like coffee packaging paper bags, flour paper bags, and seed paper bags decreases as the ink film thickness increases. This is because the ink film masks the paper's inherent high gloss, and the glossiness created by the ink film is reduced due to the paper's absorption. As the ink film thickness gradually increases, the paper's absorption of the adhesive is nearly saturated, and the amount of adhesive remaining on the paper surface increases, causing the glossiness to continue to increase.

Coated Paperboard

The glossiness of printed materials on coated paperboard increases rapidly with increasing ink film thickness. After the film thickness reaches 3.8 μm, the glossiness no longer increases with increasing film thickness.

Flexographic Printer for Pet Food paper Bag

Ink Flowability

Excessive ink flowability in flexographic printing machine can lead to larger dots, larger print sizes, and thinner ink layers, resulting in poor gloss for printed paper bags like biscuit paper bags, mooncake paper bags, and shortbread paper bags. Excessive ink flowability can result in high gloss, poor ink transfer, and poor printing quality. Therefore, to achieve optimal gloss, ink flowability must be carefully controlled, neither too high nor too low.

Flexo Printing Machinery for Dried Cranberries Paper Bag

Ink Leveling

During the flexographic printing process, good ink leveling results in a high gloss finish for paper bags like salt paper bags, dental use sterilization pouches, and medical instrument sterile pouches. Poor leveling can lead to stringing, resulting in poor gloss for products like Chinese medicine pouches, shopping paper bags, and gift paper bags.

Flexographic Press for Jewelry Paper bag

Pigment Content in Ink

Flexographic printing inks have a high pigment content, which creates numerous tiny capillaries within the ink film. However, these capillaries retain binder much more efficiently than the interfiber spaces on the paper surface absorb it. Therefore, high-pigment inks retain more binder within the ink film than low-pigment inks. Prints using high-pigment inks exhibit higher gloss than those using low-pigment inks. Therefore, the capillary network formed between the pigment particles in the ink is the primary factor affecting the gloss of paper bags such as T-shirts bags, clothing bags, shoes bags, luxury bags, and supermarket bags. In actual printing, increasing the gloss of printed products like perfume bags, cosmetic bags, and potato chip bags through varnish is fundamentally different from increasing the pigment content in the ink.

Flexography Machine for Wall Putty Powder Paper Bag

The two methods for increasing gloss should be chosen based on the ink composition and ink film thickness. Increasing the pigment content is limited by the need for color reproduction in color printing. When the pigment content decreases, the glossiness of the printed product decreases. A high gloss can only be achieved when the ink film is quite thick. Therefore, in this case, increasing the pigment content can be used to improve the glossiness of the printed product. However, the amount of pigment used can only be increased to a certain limit. Otherwise, the pigment particles will not be fully covered by the binder, which will aggravate light scattering on the ink film surface and reduce the glossiness of the printed product.

Flexographic Machine for Fertilizer Paper Bag

Ink film thickness, ink fluidity, ink leveling, and pigment content all affect the gloss of paper bags like popcorn paper bags, new year gift paper bags, and advertising paper bags. These factors work together to ensure a smooth ink film and enhance print quality, making products like Christmas gift paper bags, cement paper bags, and chemical powder paper bags more visually appealing, meeting market demands, and achieving a perfect balance between printing quality and practicality.