In the world of printing, the drying process of inks plays a crucial role in achieving high-quality results with minimal turnaround time.
Driers are catalysts that promote the oxidation of drying oils used in letterpress and offset lithographic inks.
In recent years, advancements in drier technology have significantly improved ink drying speeds, allowing ink films to dry hard within a few hours.
Liquid Driers
Liquid driers are prepared by converting organic acids into heavy-metal salts and soaps.They are soluble in oils and petroleum solvents, creating liquids or soft pastes that easily blend with inks.
Various metals are available as salts of complex fatty acids, such as octoates, resinates, naphthenates, tallates, and linoleates.
These metals are highly effective in enhancing the ink drying process.
Cobalt - The Powerful Drier
Cobalt stands out as the most powerful and popular drier.Its violet color transforms into brown upon oxidation.
While cobalt greatly accelerates ink drying, it has the downside of potentially discoloring tints and whites.
Furthermore, its solubility in organic acids makes it susceptible to the fountain solution in lithographic presses, which can lead to leaching from the ink into the fountain.
Conversely, cobalt acetate can be used to introduce drying activation into the fountain.
Manganese - A Reliable Companion
Manganese, though less vigorous than cobalt, serves as a reliable catalyst for ink drying.
Its brown color has a milder impact on whites and tints compared to cobalt.
Moreover, manganese is unlikely to leach out in the fountain solution.
In most cases, it requires heat to act as an activator, making it suitable for tin-printing inks.
Often used in conjunction with other metal soaps, manganese complements cobalt in achieving optimal drying effects.
Emergence of Cerium, Zirconium, and Lithium
Medium-efficiency driers in pale colors, cerium, zirconium, and lithium have replaced lead in many ink vehicles.They are often used in combination with cobalt or manganese soaps.
The shift from lead to these metals is driven by environmental concerns and the desire for more eco-friendly ink formulations.
Paste Driers for Multicolor Process Inks
Paste driers, prepared by grinding organic salts of lead and manganese in linseed oil varnishes, are ideal for multicolor process inks.Lead acetate and manganese borate are commonly used components in paste driers.
While they dry inks slowly, paste driers yield a receptive ink surface for superimposition, making them valuable in multicolor printing processes.
Conclusion Advancements in driers have revolutionized the ink drying process, enabling rapid and efficient drying of letterpress and offset lithographic inks.
The use of liquid and paste driers, along with various metal catalysts, has significantly enhanced print quality and production speed in the printing industry.
As technology continues to evolve, it is likely that further innovations in drier formulations will continue to improve the efficiency and performance of printing inks in the future.