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What Is Fountain Solution in Offset Printing?

Updated: Jan 31

Offset printing is a widely used method in the printing industry, renowned for producing high and consistent image quality. In the realm of this printing method, an essential component contributes to print quality – the fountain solution. So, what is fountain solution in offset printing? 


In this guide, we will explore the concept of fountain solution and discuss how it can elevate your printing process. Understanding its role and nuances is crucial for mastering the art of printing. Ready to find out more? Let’s get into it! 


What is Fountain Solution in Offset Printing
Source: shutterstock.com / Photo Contributor: zefart

What is Fountain Solution in Offset Printing? 


At its essence, a fountain solution is a water-based solution strategically employed in printing. It is formulated to dampen the lithographic printing plates before the inking rollers come in contact with them. So, what is fountain solution in offset printing used for?


The primary role of this solution is to keep the areas of the printing plate that don’t have graphics free from ink. It maintains a delicate balance between the ink and the water in the printing press. Achieving such equilibrium is essential for sharp and vibrant prints with utmost precision, minimizing the risk of smudging or ink spread. 


Understanding the nuances and optimizing its performance is critical to achieving printing perfection. For unparalleled results in commercial offset printing services, trust in our expertise. With our advanced equipment, knowledge, and commitment to excellence, we aim to elevate your prints to a new level. 


Hence, in continuation, we will explore the role and science behind such a solution to help you achieve the desired outcome.


The role of fountain solution in offset printing


Plate dampening


Fountain solution has a vital role in the plate-dampening system. The system in offset printing requires a consistent and stable supply of such a solution. The liquid wets the non-image areas of the printing plate, keeping them hydrophilic. On the other hand, the image areas treated to be ink-receptive remain hydrophobic. 


Ink repellent


As mentioned, the solution acts as an ink repellent in the non-image areas. It prevents unintended ink transfer and ensures only the image areas pick up the ink during the process of printing. 


The Science Behind the Fountain Solution


After getting familiar with the role of the fountain solution in offset printing, it is necessary to have a good understanding of its chemical composition. The offset lithography printing technique hinges on the principle that oil doesn’t mix with water. 


Since the printing press features areas that attract ink and areas that attract water, the fountain solution acts as a mediator between them. The dampening solution is applied to the entire plate with the intention of keeping the non-image areas of the printing plate moistened so they will not accept ink.


It ensures the right amount of water adheres to the non-image areas and prevents an unwanted ink transfer. The properties of this fountain solution formulation amplify the effects that make the printing process work, which is essential for keeping print quality consistent.


Fountain solution chemistry 


The fountain solution composition varies depending on various reasons. That said, most solutions comprise water, acid, gum (natural or synthetic), and surfactants. The water is the primary component of these liquids and forms the base of the mixture. 


It provides the necessary fluidity and maintains a balance between the ink and the water. The natural resin, known as gum Arabic, desensitizes the non-image areas and is added to enhance the water-retaining properties of the solution. 


It reduces the risk of plate sensitivity and creates a stable emulsion. They are included to improve the wetting properties of the solution. They lower the surface tension and allow the fountain solution to spread evenly across the plate's surface.


The solutions may also contain:


  • wetting agents (decrease the surface tension of water and water-based solutions) 

  • drying stimulator (complements the drier in the ink)

  • a fungicide (to prevent mildew and fungus in the solution) 

  • an anti-foaming agent (prevents the build-up of foam) 

  • corrosion inhibitor (prevents oxidation or other chemical reactions)


The buffer salt keeps the pH between 4.8 and 5.5, while the isopropyl alcohol is commonly in the proportion of 6% to 8%. The key to the effectiveness of this solution is using the right amount of concentration. 


Optimization technique


Achieving the optimal fountain solution performance requires careful calibration. Hence, printers commonly adjust factors like pH levels, conductivity, and temperature to fine-tune the solution. The temperature of the solution should be at about 10°C ± 2°C or about 10°C below room temperature


Maintaining the correct pH level is equally significant. This is because an unbalanced pH can lead to plate sensitivity and influence the water-ink balance. Regular testing and adjustments are essential to keeping the fountain solution within the optimal pH range to achieve consistent, high-quality prints.


How Does Fountain Solution Impact Print Quality?


Accurate image reproduction 


Efficient management of the fountain solution directly correlates to print quality. A high-quality fountain solution is crucial for accurate image reproduction. It ensures that the ink adheres only to the desired areas on the printing plate.


This often results in sharp and clear prints. Hence, a slight imbalance in the solution can cause the printing image to be imperfect. This can occur when the ink and water fail to separate adequately. 


If the pH value of the solution is too low, it can cause serious corrosion of the plate base and slow drying of the ink. Conversely, suppose it is too high (towards alkaline). In that case, it will dissolve the diazonium compound in the graphic part of the PS plate, causing the image and reducing printing quality, leading to emulsification. 


When this happens, it can often lead to poor image definition, color inconsistency, and even compromised print quality. The amount of fountain solution should be controlled based on the product image, ink color, and paper condition to ensure printing quality.


Plate longevity


Aside from image quality, a well-formulated fountain solution also contributes to the longevity of the printing plate. It prevents premature wear and damage and helps maintain consistent print quality over extended print runs.


How Does Fountain Solution Impact Print Quality?
Source: shutterstock.com / Photo Contributor: zefart

Conclusion


When it comes to offset printing, the common question of what is fountain solution in offset printing remains. This is a vital component, and its impact on the printing process is undeniable. From maintaining the delicate balance between ink and water to influencing overall print quality, understanding and optimizing fountain solutions is crucial for achieving exceptional results in the world of offset printing.


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