When flexographic printing, you have lots of choices when it comes to ink: different brands, colors, qualities, viscosities, opacities, densities and bases.
Before a printer selects the best image carrier for their flexo printing needs, they must determine the type of ink that is required. After that, the selected ink MSDS (technical data sheet), and any additives, should be sent to your image carrier manufacturer to enable the pairing of the best fit image carrier to ink.There are four main types of flexo inks:
Choosing the right ink for a specific print job depends on the desired print speeds, drying times, and chemical compatibility; substrate; maintenance and compatibility of the printing sleeves, cylinders, and plates; and regulatory compliance.
Quick Guide to The Top Four Flexo Inks
As image carrier manufacturers, our expertise is not in inks. However, we’ve included some helpful best practices to keep in mind when selecting the materials for your flexographic printing needs:
Water Based Ink
Water based ink is true to its name, and composed of mostly water and pigments -- with a few chemical additives present. Because of this composition, water based inks are considered environmentally friendly with low VOCs.
Water based inks are compatible with any type of elastomer based image carrier, and oftentimes sleeves are recommended for continuous printing.
Cleaning of the image carrier can be accomplished with a gentle soap and water solution. Recommended storage for water based inks is at room temperature, refrigerating when specified. Excessive heat is to be avoided.
UV inks are composed of monopolymers, prepolymers, photo initiators, and pigments.
UV inks are considered to be most compatible with EPDM elastomer image sleeves-- though this is not the only option. It’s always best to talk with your image carrier manufacturer about your exact press-ready ink formula when deciding on a sleeve, cylinder, or plate.
These inks contain no VOCs, and are 100% stable. Image carriers can be cleaned with non-toxic, environmentally friendly ink cleaners or alcohol based cleaners.
Store UV inks in a cool location, away from direct light.
Solvent Based Ink
Solvent based inks are composed mostly of acetates, alcohols, and pigments to give them their color.
Solvent based inks are considered to be most compatible with EPDM elastomer sleeves -- though this is not the only option. It’s always best to talk with your image carrier manufacturer about your exact press-ready ink formula when deciding on a sleeve, cylinder, or plate.
Due to the high VOC content in solvent based inks, special venting and handling is required for safe use. Cleaning of the image carrier requires the use of special volatile or non-volatile solvent ink removers, depending on the ink formula.
Solvent based inks should be stored at a moderate temperature and sealed tightly to prevent evaporation. Storage of flammable substances, like these inks, should always comply with local fire and building codes.
Oil Based Ink
Oil based inks are composed of hydrocarbons, pigments, and sometimes soy oil.
Oil based inks are considered to be most compatible with nitrile elastomer image carriers-- though this is not the only option. It’s always best to talk with your image carrier manufacturer about your exact press-ready ink formula when deciding on a sleeve, cylinder, or plate.
Cleaning of the image carrier requires the use of an approved solvent or non-volatile cleaning solution, depending on the ink formula.
When oil based inks are combined with harsh solvents, they should be handled with extreme care while wearing protective gear.
Always Read Manufacturers' Labels and Follow Your Facility's Flexo Ink Storage Policies and Procedures
Mixing inks can cause dangerous chemical reactions, ruin equipment and supplies; and ink left on image carriers and other press components can negatively affect print jobs.
To extend the life of your printing components, create a safe work environment and ensure the quality of each print run -- each printing press ideally should use a dedicated ink type or be thoroughly cleaned between print jobs using different inks.
Printing facilities should have written Spill Prevention, Control and Countermeasures (SPCC) plans designed to protect the environment and preserve the quality of ink, while also ensuring safe storage and handling.
For more information about different flexographic printing inks and how to effectively pair them with different types of image carriers, contact your flexo industry experts at Luminite today.