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What Are Printing Plates?

Updated: Jan 31

While you may have heard about printing plates, you may not know what they are. From newspapers to clothes, printing plates play a key role in creating printed materials we see daily. So, what are printing plates? What are printing plates made of?


That is why we will explain everything about printing plates, such as how many types are there and how they are made.


What Are Printing Plates
Source: shutterstock.com / Photo Contributor: Levent Konuk

What Are Printing Plates?


Printing plates are essential components in the printing industry. They are flat sheets or cylindrical metal surfaces. Their role is to transfer the text or image onto the printing surface, so you can print using different printing techniques, such as digital printing, flexo printing, and offset printing


Printing plates are commonly used for printing bags, clothing, magazines, and catalogs, and they play a crucial role in delivering high-quality prints with precision and accuracy. Printing plates are important because they serve as a medium between the image and the printing press.


As a reliable printing company, we offer high-quality print and finishing solutions, and we work with different printing techniques. That is why we have the knowledge and experience about every detail in the printing industry.


How are printing plates made?


Printing plates are metal plates usually made of aluminum. The process of making printing plates includes three stages: mining, production, and prepress. 


The process begins with bauxite that is mined and sent to refineries. The aluminum is in the bauxite. Then, it follows the refining, where the bauxite is mixed with caustic soda and steam. Next comes the smelting, when a big smelting refinery prepares the aluminum for an electrolysis process.


The aluminum is shipped from the refineries in casting slabs. The last step before the shipping is pre-heating and hot rolling/cold rolling. This involves pressing the long sheets and forming them into rolls by heating/cooling.


The next stage is when the aluminum rolls reach the printing plate supplier, which will make the printing plates. Several important steps in this stage are etching, cleaning, graining, drying, and anodizing. 


Shortly put, aluminum oxidizes when in contact with air, and etching removes the oxide layer. Also, the surface must be cleaned before graining. Graining is a process that makes the surface more hydrophilic. So, once it is dried, the surface undergoes anodization, making it more durable and corrosion-resistant.


The final phase of prepress includes burning, developing, and mounting. All these stages are done in the printing company.


What are the three types of printing plates?


Three main types of printing plates are used in the printing industry: thermal plates, flat sheets, and metal plates.


Thermal plates


Thermal plates are used in digital printing and are efficient and fast. They are called thermal plates because they use a thermal process to transfer the image onto the printing surface. 


The plates are exposed to a digital image using laser technology, and the heat from the laser transfers the image onto the plate. Next, the image is engraved onto the plate, and when heated, the image areas receive ink. 


Then, the heated areas attract ink, which is transferred to the printing substrate. Moreover, the image is transferred to the printing substrate using a series of rollers and heat.


Thermal plates
Source: shutterstock.com / Photo Contributor: Ivan Kulikov

Flat sheet plates


Flat sheet plates, called lithographic plates, are mainly used in offset printing. These plates are usually made of aluminum or polyester. 


So, the image is applied to the surface of the plate using lithographic processes. Usually, there is one plate for every color in the design that should be printed.


Furthermore, the image is transferred from the plates to a rubber-blanked cylinder, which transfers the ink to the printing substrate. The areas that are meant to resist ink are treated to be hydrophilic, while the image areas are made hydrophobic. Simply put, this creates a perfect balance.


Flat sheet plates
Source: shutterstock.com / Photo Contributor: Levent Konuk

Metal plates


Metal plates are usually used in flexographic printing. These plates are made of a metal surface, usually steel or aluminum. 


The image is etched onto the plates using a laser or a chemical process. After that, the cylinder rotates, and the ink goes into the image areas, which are then transferred to the substrate. 


These metal plates are incredibly durable. They can withstand high pressures and extended use on printing presses.


Metal plates
Source: shutterstock.com / Photo Contributor: RossEdwardCairney

Conclusion


What are printing plates? Now you understand that they are an indispensable part of the printing industry. 


They come in three types: thermal plates, flat sheets, and metal plates, each suited for a different printing technique. Overall, printing plates ensure high-quality prints and efficient production.


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