Printed Plastic Bags
A critical factor in modern marketing is brand identity and recognition. The proper placement of a logo or slogan makes it easier for customers to find a product. Additionally, having a logo or slogan that has appeared in the media coordinated with packaging enhances the viability of a product and its promises. One of the methods used to complete the process of brand identification is printing of logo or slogans on plastic bags used to package and present a product or to associate a product with retailer.
Quick links to Printed Plastic Bags Information
How Plastic Bags are Printed
Printing on plastic bags has become a widely used marketing tool that provides visibility and product recognition. The appearance of a logo or slogan on a plastic bag serves as a method for promoting a product using a creative and eye appealing presentation. Regardless of the size of your organization, printing on plastic bags can assist in building your brand and help customers remember who you are and your products.’
The printing process for plastic bags involves the use of several printing methods. The determination of the method used is dependent on the number of bags to be printed with short run using one process while long runs of several thousand using another process. A further division of plastic bag printing is the random and registered methods.
With random printing, the image to be placed on a bag is printed a certain number of inches. The placement can be in several positions and in different places. It is a very fast printing process and very efficient. When an image has to be placed in the same spot on every bag, registered printing is used. During the printing, the image positioned in a specific spot during printing and appears in the same place on every bag. This process is possible through the use of an eye mark in the shape of a rectangle, which helps align the colors properly. In addition, the eye mark signals the sealer and cutter to ensure every bag has the same placement of the image.
Flexography
Flexography is a high-speed printing method that uses a plastic roll feed and used to print high volumes of plastic bags at a rate of 2000 linear feet per minute. A set of photopolymer plates are positioned on several cylinders with each plate having one of the colors for the image to be created. The images and text to be printed are raised off the plate, which ensures that only the raised portion makes contact with the plastic material.
A fountain roller collects ink from an ink pan and passes it on to an ink metering roller that delivers it to the plate cylinder. As the plastic from the plastic roll moves past the plate on the cylinder, an impression cylinder uses pressure to transfer the ink from the plate to the surface of the plastic. The ink transfer process controls the amount of ink to ensure the proper thickness of ink is placed on the plate.
There are three types of ink that are used with the flexographic printing process, which are water based, solvent based, and energy curable. Of the three, solvent based inks are used to print on plastic bags, since they dry quickly, adhere to the plastic, are resistant to fading and smudging, and resistant to abrasions and chemicals.
Gravure Printing
Gravure printing is a very old printing process that involves engraving the image to be printed on a cylinder or printing plate. The process was originally used to print magazines and newspapers in color over one hundred years ago. The images printed using gravure printing have deep rich, vibrant colors. Gravure plastic bag printing is used for high volume printing due to the expense of creating the printing cylinders.
The full name of gravure printing is rotogravure due to the fact that the etched plate is placed on a cylinder that rotates as it applies the text and image to the plastic material. Gravure cylinders are made of steel and plated with copper. A chemical etching process is used to place the text and images on the cylinder, a process that involves placing images and text on the cylinder using ultra violet light where a chemical etchant removes material from unprotected portions of the cylinder and leaves the images and text.
Cells that are etched into the cylinder control the amount of ink that is transferred to the surface of the plastic. As the cells get deeper, the intensity of the colors transferred increases. This aspect of gravure printing requires process control during etching and engraving to ensure proper cell depth.
As with flexographic printing, solvent inks are used, since they easily adhere to the surface of the plastic. Solvent inks are pigment inks that use oil or alcohol as a carrier for the ink. This factor is the reason that they are more permanent than water-based inks and why they work well with plastics.
Screen Printing
Screen printing is another old method of printing that has existed for many years. It is a simple process that has become a favorite of DIY enthusiasts and is ideal for short printing runs. Screen printing is a labor-intensive time-consuming process that is used to place images on individual bags. It has the ability to place an image and text in the exact location on every plastic bag, much like the registered printing process of flexographic printing. Screen printing does not involve the use of rolls of plastic but places images on one bag at a time.
The screen-printing process involves placing a screen with an image and text onto the surface of a place bag. The screen with the image is held in place by a frame, which stretches the screen such that the screen even and flat. The fabric of the is made of silk, synthetic materials, or other forms of porous materials. Images can be painted on the screen or transferred using photo sensitive emulsion. For plastic bag printing, photo emulsion is very common since it does not involve hand labor. The initial image is normally created on a computer using one of the versions of design software.
The transfer of the image and text involves the use of a photo sensitive emulsion applied with a scoop coater. Once the emulsion dries, the design is placed on the screen. The screen is exposed to ultra violet light where the image keeps the emulsion from hardening while the unprotected emulsion hardens and becomes non-porous. The emulsion protected by the image is washed away such that the portion protected by the image is porous and will allow ink to pass through.
The developed screen is placed over a flattened plastic bag, ink is applied by hand, and the image is transferred to the surface of the plastic bag. In order to use multiple colors, a screen created for each the colors. Much like flexographic printing and gravure printing, the images and text created by screen printing are vibrant and bold.
Heat Press Plastic Bag Printing
Heat press printing is used on thicker plastic materials that can withstand the amount of heat produced by the process. The key to the process using choosing the right machine and temperature, since they can influence the quality of the printing. With a heat press, heat and pressure is used to place an image or text on a plastic bag.
Once the design is created, it is placed on transfer paper or film using a special type of ink. The created design on the paper or film is placed on a plastic bag that is positioned on a heat press machine that resembles a large hot iron. The heated portion of the heat press is lowered onto the design and plastic bag, which causes the ink to transfer from the paper or film onto the plastic bag.
The heat press process takes several forms and includes a screen-printing heat transfer method. In each of the methods, close monitoring of the temperature is necessary to avoid damage to the plastic bag. As with screen printing, heat press printing is a labor-intensive process and time-consuming process that is used for short runs of plastic bags.
The four methods for plastic bag printing that are described above are some of the most common methods. There are several methods that are used. Plastic bag manufacturers use printing methods that best fit the design of their manufacturing processes and the types of bags they produce.
Types of Printed Plastic Bags
There are an endless number of shapes, forms, styles, and types of printed plastic bags. They are one of the most ubiquitous forms of packaging material in the world. Regardless of the many forms, all types have the purpose of placing a logo, brand, image, or slogan in the public eye. The style and design of the bags being used is in accordance with the message being delivered.
Gusset Bags
One of the more popular forms of printed plastic bags is gusset bags that expand on both sides of the bag to offer more interior room. The folded sides of a gusset bag expand to increase the interior area of the bag. This design is referred to as a gusset and is engineered into the bag during the forming process. Gusset bags are very popular at retail outlets since they make it possible to package more goods.
Die Cut Handle Bags
Die cut handle bags have a handle cut into the surface of the bag for easy carrying of the bag. They can also be gusseted bags and are commonly used by clothing and department stores. The material used to produce die cut handle bags is normally one of the forms of polyethylene with high density polyethylene bags being heavier and sturdier than low density polyethylene ones.
Resealable Bags
The initial use of resealable bags was for storing leftovers and packing lunches. They were and are very plain bags that have a strip across the top that is pressed to seal the bag. In recent years, manufacturers have printed images and text on these simple bags as a form of entertainment and to provide information about the contents. The new iteration of resealable bags has the same sealing method with the addition of colorful designs and images.
Loop Handle Bags
Loop handle printed plastic bags are reusable bags that can be gusseted like gusseted bags and die cut handle bags. Unlike die cut handle bags, the handle for loop handle bags is on the top and outside the bag and can be cut into the bag material or attached after the bag is formed. They are a highly durable form of plastic bag that can be used multiple times for several applications. Loop handle plastic printed bags are very popular and widely used by several retail and commercial enterprises.
Drawstring Bags
Drawstring printed plastic bags are made from highly durable low-density polyethylene, which gives them strength, durability, and protection for their contents. The drawstrings for drawstring printed plastic bags are made of plastic polyethylene tape or cotton fabric and are designed to securely close the bag. As with all forms of printed plastic bags, drawstring plastic bags come in several sizes including gusset types for bulky and awkward materials. Drawstring plastic bags have a clear or white surface that is easy to print on and provide a highly visible image.
Garment Bags
There are several forms of garment bags, all of which have some form of printing to identify the company for which the bags were manufactured. The two most common forms of garment bags are those that are used by dry cleaners, which are very lightweight and stretched over the top of clothing, and heavier plastic garment bags that are made of heavy durable plastics with a zipper for opening the bag. Garment bags are made to protect clothing and provide an easy method for transporting clothing.
Wicket Bags
Wicket plastic bags are a convenient and efficient method for storing and organizing plastic bags. They have a form of bracket made of metal or other type of material that is used to organize and secure the wicket bags in groups. The bracket holds the plastic bags securely until they are ready to be used. The bags can be pulled from the wicket or lifted off the wicket to be filled with a variety of items. They make it possible to rapidly and quickly package purchases or products for shipping.
The printed plastic bags that are described above are a small sampling of the many styles, types, designs, and shapes of plastic printed bags that are available. Manufacturers are constantly developing new and innovative types of printed plastic bags to advertise products and place logos and slogans in the public eye.