Flexographic Printing: The Role of Inks and Solvents

Flexographic Printing Machine

The Impact of Inks and Solvents in Flexographic Printing

Flexographic printing is now a staple of custom label printing, enabling efficient and high-quality results. However, part of the success of flexographic printing hinges on the interplay between inks and solvents. These crucial components directly impact print quality, adhesion, and environmental sustainability. So, let’s dig into things that relate to inks and solvents.

The flexographic print industry is rapidly turning towards sustainable inks for printing needs which are also better for the environment.  These types of inks offer an advantage to printers as well.  Since they are not made with hazardous materials, like solvents of petroleum products, they require less energy and fewer resources compared to conventional inks.

Flexographic Ink Categories

Flexographic inks are categorized into two types.

  • Volatile inks – These are water-based, oil-based, and solvent-based. These inks through absorption and evaporation will set and dry.
  • Curable inks – UV/EB and LED Inks which when exposed to ultraviolet (UV) light or electron beam (EB) will set and dry.

Types of Inks and Solvents

Flexographic ink is an amalgamation of resins, pigments, additives, and solvents.

Types of Inks and Solvents

To make the best choice, one needs to know the inks and coatings adhesion to the substrate.  Dyne is a surface energy and an adhesion measurement used in the industry. A lower dyne level ink to a high dyne level substrate is ideally the best application. For example, when choosing less absorbent substrates (film, foil), this will require a curable ink that dries fast such as solvent or UV-based inks for a good print quality.

Ink and substrate choices

Flexographic inks can be water-based, solvent-based, UV-based, or oil-based.

UV Inks (curable)

UV inks have gained prominence in flexographic printing due to their rapid curing process and exceptional color vibrancy. These inks contain photoinitiators that remain inert until exposed to ultraviolet (UV) light. Once exposed, UV inks polymerize instantaneously, resulting in a durable and glossy finish. UV inks’ quick curing times are thanks to high-intensity UV lamps.

Additionally, UV inks are known for their excellent adhesion to a wide array of substrates. However, you must be cautious of potential environmental concerns associated with the use of UV inks, such as the emission of volatile organic compounds (VOCs) during the curing process.

LED Inks (curable)

LED inks have emerged as a more sustainable alternative to traditional UV inks. These inks employ light-emitting diodes (LEDs) for curing, offering reduced energy consumption and diminished environmental impact.

LED lamps emit narrower wavelengths of light compared to conventional UV lamps, allowing for precise curing without generating excessive heat. This not only contributes to energy efficiency but also enables a broader range of compatible substrates. The reduced heat emission also facilitates printing on heat-sensitive materials. LED inks provide excellent adhesion, color accuracy, and overall print quality.

Oil-Based Inks (volatile)

These inks are a mix of hydrocarbons, pigments, and oil (often soy oil or mineral oil). They are best used in the publication print industry.

Water-Based Inks (volatile)

Water-based inks are recognized for their eco-friendliness and low VOC emissions. These inks utilize water as the primary solvent, reducing the need for more volatile organic solvents. Water-based inks are also inherently safer for both the environment and workers. They are particularly suitable for printing on porous substrates like paper and cardboard.

The curing of water-based inks is typically accomplished using blowers that facilitate the evaporation of water content, leaving behind the pigments and binders. But while water-based inks offer environmental benefits, they may require longer drying times compared to UV and LED inks.

Role of Solvents in Flexographic Printing

Solvents play a crucial role in flexographic printing by influencing ink properties. This includes viscosity, drying time, and adhesion. These chemicals can be added to inks during the ink formulation process to achieve the desired appearance. In some cases, while the job is running on the press, adjustments may be made to fine-tune ink properties.

Common solvents used in flexographic inks include:

  • Water: Used as a solvent in water-based inks.
  • Ethyl Alcohol: Employed as a solvent to adjust ink viscosity and improve drying.
  • Ethyl Acetate: Used for viscosity adjustment and as a fast-evaporating solvent.
  • Methoxy Propyl Acetate: Known for its slower evaporation rate, suitable for extending drying time.
  • Ethyl Alcohol-Ethyl Acetate Mix: A blend that balances fast drying with improved adhesion.

Comparative Analysis & Considerations

Selecting the right type of ink and solvent in flexographic printing is a critical decision that can significantly impact print quality, production efficiency, cost, and environmental sustainability. Each type of ink and solvent combination has its advantages and drawbacks to consider. So, here’s a breakdown of the comparisons between label printing inks and solvents:

UV Inks


  • Rapid Curing: UV inks cure almost instantaneously under UV lamps, leading to faster production speeds.
  • High Print Quality: UV inks provide sharp and vibrant colors with excellent adhesion to various substrates.
  • Versatility: Suitable for a wide range of applications and substrates, including plastics, labels, and packaging.
  • UV lamps can cure both UV and LED inks and coatings.


  • Environmental Impact: UV inks can emit volatile organic compounds (VOCs) during curing, posing potential environmental concerns.
  • Limited Substrates: UV inks may not be ideal for heat-sensitive materials due to the heat generated by UV lamps.
  • Higher ink and equipment costs, for example, installing and maintaining UV curing can be expensive.

LED Inks


  • Energy Efficiency: LED lamps consume less energy and emit less heat compared to UV lamps, reducing operational costs.
  • Sustainability: LED inks have a lower environmental impact due to reduced energy consumption and 99.5% less VOC emissions.
  • Wide Compatibility: LED inks are suitable for various substrates and heat-sensitive materials.


  • Higher Initial Costs: LED curing equipment may have a higher upfront investment and maintenance cost.
  • Slower Curing: LED inks may require slightly longer curing times than UV inks.
  • LED lamps will not cure UV inks and coatings.

Oil-Based Inks


  • Best paired with substrates like newsprint since they adhere to materials primarily through absorption


  • These inks create VOCs (Volatile Organic Compounds) that are pollutants to the environment and hazardous to handle.
  • There are regulated guidelines for storage and clean-up for safety and environmental considerations.

Water-Based Inks


  • This is the most popular choice and the most sustainable option since they can easily blend with ingredients like algae cells, to create a more sustainable product.
  • Eco-Friendly: Water-based inks have minimal VOC emissions, making them an environmentally responsible choice.
  • Safe: These inks are safer to handle.
  • Substrate Compatibility: Ideal for porous substrates like paper and cardboard.
  • Low ink cost.


  • Drying Time: Water-based inks typically require longer drying times compared to UV and LED inks, potentially impacting production speed.
  • Limited Compatibility: Not suitable for all substrates, particularly non-porous materials.



  • Viscosity Control: Solvents allow for precise adjustment of ink viscosity, crucial for achieving the desired print quality.
  • Drying Time Control: Solvents can be used to modify drying times, aiding in production flexibility.


  • Environmental Concerns: Some solvents can contribute to VOC emissions and pose environmental risks if not managed properly.
  • Potential Health Risks: Solvent exposure can pose health hazards to workers if not handled with care.

LED and water-based inks ultimately stand out for their reduced environmental impact and safety benefits and solvents help fine-tune these details.

In conclusion, inks and solvents play an important role in determining lead time, substrate choice, and print quality.


Adapting to Alternative Flexo Ink Options

Vegetable-based inks are derived from organic compounds (corn, soybean) that are designed to reduce VOCs and are easily recyclable.

Algae inks are super sustainable and believe it or not, have a negative carbon footprint – they do more for the environment and are UV resistant.


Why Kwality Labels for Your Flexographic Printing Needs

Inks and solvents are one of the driving forces behind the success of flexographic printing. The dynamic interaction between these components influences everything from print quality to environmental sustainability. This is why experienced professionals at Kwality Labels are the key to pairing the right inks with the right substrate for the best-printed result.

Our team of label printing Toronto experts at Kwality Labels provides an abundance of services to bring your visions to life. Discover how we can serve you by getting in touch today. Together, we can create a more colorful and eco-friendly world of custom labels.