The Ultimate Guide to Choosing the Best Printing Inks for Packaging

What To Consider When Selecting Printing Inks for Packaging Applications

Simply put, there is no “general purpose ink” when it comes to product packaging. Factors like substrate choice and environmental conditions can all render one formula useless for an application while making another one a perfect fit. In a world where legible lot codes and machine-readable barcodes are required for effective distribution, packaging companies have no choice but to perform careful ink research before marking their product lines.

To ensure that all product codes are fully legible and long-lasting, one needs to consider the following ink qualities:

• Substrate Compatibility: All packaging materials have their own unique surface properties that affect ink adherence, legibility, and drying times. Consequently, an ink that works well with a porous material like cardboard likely won’t work at all with a non-porous material like plastic or metal.
• Workplace Conditions: Industrial product coding often occurs in facilities filled with harsh conditions. Industries like wire/cable extrusion, chemical production, and electrical component manufacturing, for example, all commonly deal with high levels of dust and airborne particles. Additionally, beverage and food canning groups often struggle with excessive moisture levels and extreme temperatures, both high and low. If an ink formula isn’t able to resist these elements, any applied codes are liable to become messy and hard to read.
• External Environmental Conditions: Are your products likely to be exposed to long periods of sunlight or rough physical handling? To ensure lasting code readability, you will need an ink specifically formulated to withstand these environmental hazards.
• Code Contrast: Contrast is defined by how much an applied ink stands out from the substrate surface. While all markings need a minimum amount of contrast to be legible to the human eye, certain markings require a higher level of contrast than others. Barcodes and data matrices, for instance, require substantial contrast to be machine-scannable.

By considering each of these factors, one can find the perfect ink to create long-lasting codes and comply with modern traceability requirements. Other important considerations include:

• Upfront Ink Cost: Not all inks cost the same, and if you’re using an expensive original equipment manufacturer (OEM) formula, there’s likely a more affordable alternative on the market.
• Cost of Operation: Some ink formulas can influence a printer’s ongoing maintenance needs. For example, pigmented inks may cause CIJ printers to require more frequent servicing than dye-based inks.

With all of these elements in mind, we’ll now take a look at the printing needs of five of the most popular packaging substrates: plastic, flexible film, cardboard, glass, and aluminum.

Inks for Printing on Rigid Plastic

Rigid plastic is one of the most versatile substrates in the world. Used to create water bottles, medicine bottles, detergent jugs, and much more, rigid plastic is valued for its cost-effectiveness, durability, and high recyclability. To create these forms of plastic packaging, manufacturers can use a few different types of rigid plastic, with the most common being polyethylene (PE), high-density polyethylene (HDPE), polypropylene (PP), and polystyrene.

Although these different types of plastics vary in certain properties like density, stiffness, and optical clarity, they are all still non-porous substrates. As such, they can generally all be marked by the same ink formulas.

For non-porous materials like rigid plastic, the best ink choices will be fast-drying, solvent-based formulas as opposed to water-based inks. Water-based formulas are designed to sink below the surface of porous materials to dry in a clear, well-defined manner. Non-porous materials don’t allow ink to sink beneath the surface.

Consequently, if a company attempts to use a water-based formula on material like rigid plastic, the applied codes are likely to become messy and difficult to read. Formulas with methyl ethyl ketone (MEK), ethanol, ethyl acetate, and methanol bases can dry more quickly than water-based formulas and thus create well-defined codes on non-porous materials.

At InkJet, Inc., we carry a large number of solvent-based formulas for continuous inkjet (CIJ) and thermal inkjet (TIJ) printers, many of which are also compatible with popular printers from companies like Videojet, Markem-Imaje, and Domino. Some of our most popular plastic packaging printing inks include:

• OS505, a black MEK-based formula that is compatible with Videojet 1000 Series printers and ideal for humid environments.
• IMA50, a black ethanol/acetone-based formula that is compatible with Markem-Imaje printers.
• DOM i236, a black MEK/ethanol-based formula that is compatible with Domino A-Series CIJ printers.

Inks for Printing on Flexible Packaging and Film

Flexible packaging is an umbrella term that refers to several plastic-based forms of product packaging. Used to create bags, stand-up pouches, blister packs, film-covered trays, and more, flexible packaging is a staple of many industries ranging from pharmaceutical development to food production.

While flexible packaging is created from different types of plastic than rigid packaging, they are still non-porous. Accordingly, most forms of flexible packaging like bags and pouches also respond well to the solvent-based formulas used to mark rigid packaging.

In addition, there are several solvent-based inks specifically designed for film applications. Our available flexible packaging-compatible inks include:

• OS411, a black MEK-based ink that offers a drying time of fewer than 2 seconds and is compatible with Videojet printers.
• DOM i222, a black MEK-based ink that is perfect for printing on coated plastic cards and is compatible with Domino A-Series CIJ printers.
• VW682, a retort-proof MEK-based ink made that is designed for flexible film applications and is compatible with Videojet printers.

On top of CIJ and TIJ ink options, we also offer wax and resin-covered ribbons for thermal transfer overprinters.

Inks for Printing on Glass

Glass is another multi-purpose product packaging material that is used by a wide variety of industries. Like plastic, glass is a non-porous substrate that responds well to solvent-based ink formulas. While there are many glass-compatible ink formulas available today, they are not all ideal for the same worksite conditions.

For example, beverage bottling is one of the most common uses for glass packaging. During the beverage bottling process, operators often have to deal with substantial amounts of humidity, bottle condensation, and possibly high/cold temperature fluctuations. Each of these factors has the potential to make codes appear muddled, faint, or altogether unreadable.

To ensure that glass codes appear as clean as possible, InkJet, Inc. offers:

• OS420, a black MEK-based ink specifically designed for returnable bottles after many cycles.
• LIN85 YEL, an easy maintenance yellow for condensation on returnable bottles.
• Dom i304, a thermochromic ink that can withstand steam sterilization.

Inks for Printing on Cardboard

Cardboard is without a doubt one of the most important materials in modern commerce. According to experts, over 95% of all products within the United States are shipped using cardboard boxes, making the material essential to the success of distribution networks and supply chains around the world.

Of course, cardboard boxes can only effectively serve as shipping containers if they are outfitted with clear text and machine-scannable barcodes.

Unlike rigid plastic and flexible packaging/film, cardboard is a porous substrate. As such, water-based inks are ideal if one is marking the material with a CIJ or TIJ printer.

Traditionally, CIJ and TIJ printers have been the go-to options for directly placing text on cardboard materials. However, CIJ printers and most TIJ printers aren’t capable of making large images or high-contrast barcodes on cardboard due to their printhead configurations and ink selection—although there are exceptions, as in the case of the Anser X1 TIJ printer. For large image and barcode applications, companies should opt for a high-resolution case coder like the Precision Series 72. These printers use oil-based inks that are capable of creating higher-contrast images than CIJ and TIJ printers. Their larger piezoelectric printheads also enable users to create bigger images than most CIJ and TIJ printers can match.

InkJet, Inc. carries cardboard-compatible formulas for CIJ, TIJ, and case-coding printers to meet different primary and secondary packaging needs.

Inks for Printing on Aluminum

Aluminum cans have become ubiquitous in today’s packaging industry as they can store paint, chemicals, soda, beer, and various food items.

Like glass bottles, aluminum cans are non-porous packages that are filled in facilities that are frequently home to challenging environmental elements. Extreme temperatures, humidity, and unique post-processing needs are common and must be considered to ensure marking success.

Fortunately, InkJet, Inc.’s ink portfolio is filled with formulas that are ideal for marking aluminum cans. Available options include:

• DC301, an MEK/Methanol-based ink with thermochromic properties that benefit the retort process. 
• DOM i227FT, a black MEK-based ink similar to Domino’s IC-227BK that is resistant to alcohol and heat.
• OS459, black MEK-based ink similar to VideoJet’s V459-D that offers excellent adhesion to aluminum and can resist heat up to 150 F.