Dry Offset
A little History
Dry offset printing is a variation of offset printing and flexo printing that specifically addresses the challenge of printing on non-absorbent surfaces, such as metal and plastic. Dry offset printing has carved a niche for itself in the printing industry, providing a specialised solution for applications that require precise and high-quality printing on materials that do not readily accept traditional inks. Its continued use in packaging demonstrates its effectiveness in meeting specific market demands.
Early 20th Century Beginnings:
Dry offset printing emerged in the early 20th century as an adaptation of the offset printing process.
The primary challenge addressed by dry offset was the need to print on materials that did not absorb ink well, particularly metal and certain types of plastics.
Focus on Metal Packaging:
Dry offset printing gained traction in the packaging industry, particularly for metal containers such as cans and tubes.
Its ability to adhere ink to non-absorbent surfaces made it suitable for the decoration of metal packaging.
Advancements in Plate Technology:
Similar to offset printing, dry offset printing relies on plates. The plates used in dry offset printing are often made of rubber or plastic, and the ink is transferred from the plate to an intermediate surface (usually a rubber blanket) before reaching the final substrate.
Applications in Plastic Products:
Dry offset printing found applications beyond metal packaging and extended to printing on certain types of plastics, such as cups, containers, and lids.
The process became popular for items like plastic drink cups used in the food and beverage industry.
Quality Improvements and Color Capabilities:
Over time, advancements in technology and plate materials improved the print quality and color capabilities of dry offset printing.
The process became more versatile, allowing for the printing of intricate designs and multicolour images.
Automation and Efficiency Improvements:
Like other printing technologies, dry offset printing has benefited from automation and technological advancements.
High-speed dry offset printing presses have been developed, enhancing efficiency in large-scale production.
Ongoing Relevance in Packaging:
Dry offset printing remains relevant in the packaging industry, particularly for products that demand high-quality and durable printing on non-absorbent surfaces.
It is commonly used for decorating cylindrical or cup-shaped containers, such as beverage cups, cosmetic packaging, and certain types of industrial containers.
Some Applications of Dry Offset Printing in Packaging
Dry-offset printing is particularly advantageous for packaging applications involving three-dimensional objects and containers with curved or irregular surfaces. It provides good ink coverage, precise image reproduction, and durability, making it a preferred choice for certain packaging needs. The process is especially suitable for high-volume production of containers commonly used in the food, beverage, and personal care industries.
Metal Packaging:
Metal Containers: Dry-offset printing is commonly used for printing on metal packaging, such as aerosol cans, paint cans, beverage cans, and metal tubes. It provides durable and high-quality graphics on flat or curved surfaces.
Plastic Packaging:
Plastic Containers: Dry-offset printing is suitable for printing on plastic containers, including cups, lids, and tubes. It is often used in the packaging of food, cosmetics, and personal care products.
Closures and Caps:
Bottle Caps: Dry-offset printing is employed for printing on closures and caps, providing detailed and precise graphics on the tops of bottles and containers.
Drinkware Printing:
Mugs and Tumblers: Dry-offset printing is utilised for printing on drinkware made of plastic or metal, offering a cost-effective solution for custom branding.
Glass Containers:
Glass Bottles: While not as common as other printing methods for glass, dry-offset printing can be used for certain types of glass containers, particularly those with a cylindrical shape.
Containers with Irregular Shapes:
Specialty Packaging: Dry-offset printing is well-suited for containers with irregular shapes or non-flat surfaces, allowing for consistent and high-quality printing on these unique packaging formats.
Toy Packaging:
Toy Packaging: Dry-offset printing is used for printing on packaging materials for toys and games, providing vibrant and detailed graphics.
Automotive Packaging:
Automotive Parts Packaging: Dry-offset printing is employed for printing on packaging materials for automotive parts, especially when the parts have complex shapes.
Cap Liners and Seals:
Sealing Materials: Dry-offset printing can be applied to print on cap liners and seals used for sealing containers, ensuring a branded and secure packaging solution.
Other applications of dry-offset printing
Promotional Items:
Promotional Products: Dry-offset printing is used for customising promotional items made of plastic or metal, such as pens, keychains, and reusable cups.
Electronics:
Printed Circuit Boards (PCBs): Dry-offset printing is used for printing on PCBs, providing a method for applying identifiers and graphics.
Electronic Components: Dry-offset is employed for printing on various electronic components where precise and durable printing is required.
Toys and Games:
Plastic Toys: Dry-offset printing is used for printing on plastic toys, providing vibrant and detailed graphics.
Game Components: Dry-offset is employed for printing on game components, including cards, dice, and other elements.
Automotive Parts:
Automotive Trim: Dry-offset printing is applied for printing on automotive trim components, providing decorative elements for interior and exterior parts.
Hubcaps: Graphics and logos on hubcaps are often produced using dry-offset printing.
Medical and Laboratory Products:
Plastic Labware: Dry-offset is used for printing on plastic labware items, such as Petri dishes and test tubes.
Medical Packaging: Dry-offset printing is applied to medical packaging, especially on non-absorbent materials.
Food Service Items:
Disposable Plates and Cups: Dry-offset printing is used for printing on disposable plates and cups made of plastic or other non-absorbent materials.
Main Substrates used in Dry Offset Printing for Packaging
Dry-offset printing is a specialised printing process often used for three-dimensional objects, such as cylindrical containers and lids. It utilises a printing plate and a rubber blanket to transfer ink onto the substrate. The choice of substrates and inks in dry-offset printing depends on the specific requirements of the packaging.
Metal Packaging:
Aluminum: Dry-offset printing is commonly used for printing on aluminum cans, lids, and other metal packaging, providing a durable and visually appealing finish.
Tinplate: Used for printing on metal containers, such as cans for food and beverages.
Plastic Packaging:
Polypropylene (PP): Commonly used for lids and closures.
Polyethylene (PE): Used for printing on certain plastic containers and lids.
Polystyrene (PS): Applied to plastic containers used in the packaging of various products.
Paperboard:
Folding Cartons: Dry-offset printing is suitable for folding cartons made of paperboard, commonly used in packaging for food, cosmetics, and other consumer goods.
Textiles:
Textile Packaging: Dry-offset printing can be applied to textiles used in packaging, such as cloth bags and pouches.
Glass Containers:
Glass Bottles and Jars: While less common than for other materials, dry-offset printing can be used for certain types of glass packaging, especially for high-end products.
Inks, Coatings and Lacquers
In dry-offset printing for packaging, various primers, lacquers, varnishes, inks, and special coatings are utilised to achieve specific visual effects, enhance durability, and provide protection to the printed material. The selection of these components depends on factors such as the substrate material, the printing technology, and the desired characteristics of the packaging. These coatings and inks contribute to the overall appearance, functionality, and durability of dry-offset printed packaging materials. The choice of each component depends on the specific requirements of the packaging application, the characteristics of the substrate, and the desired visual effects. Dry-offset printing's suitability for three-dimensional objects, such as cylindrical containers and lids, allows for the use of a wide range of coatings and inks to achieve diverse packaging solutions.
Primers:
Purpose: Primers are applied as a pre-treatment to improve adhesion, ink absorption, and durability on the substrate.
Types:
UV-Adhesive Primers: Enhance adhesion of UV-curable inks on non-porous surfaces like plastics and metals.
Water-Based Primers: Improve ink adhesion on paper and cardboard substrates, commonly used in dry-offset printing.
Lacquers and Varnishes:
Purpose: Lacquers and varnishes provide protective coatings over the printed surface, enhancing visual appeal and offering additional functionalities.
Types:
Gloss and Matte Varnishes: Applied over the printed surface for gloss or matte finishes, providing protection and improving aesthetics.
UV-Curable Clear Coats: Offer added protection, gloss, and durability, especially for UV-curable inks.
Specialty Varnishes: Include formulations for specific effects like textures, textures, or scratch resistance.
Inks:
Purpose: Inks are the actual printing materials that create the images on the packaging substrate.
Types:
Oil-Based Inks: Traditional oil-based inks are commonly used in dry-offset printing for their versatility and print quality.
UV-Curable Inks: Cure instantly under UV light, offering high colour vibrancy and durability on various substrates.
Specialty Inks: Include metallic inks, fluorescent inks, and other specialty formulations for unique visual effects.
Special Coatings:
Purpose: Special coatings add unique visual effects or provide specific functionalities to the printed material.
Types:
Soft Touch Coatings: Add a tactile and soft feel to the packaging surface.
Scratch-Resistant Coatings: Enhance durability by protecting against scratches and abrasions.
Glow-in-the-Dark Coatings: Create phosphorescent effects for attention-grabbing packaging.
Thermochromic Coatings: Change colour with temperature variations, adding an interactive element to the packaging.
Textured Coatings: Add texture and dimension to the printed surface for a unique look and feel.
Anti-Microbial Coatings: Provide protection against microbial growth on the packaging surface.
Anti-Counterfeiting Coatings: Include features such as holographic effects or invisible inks to deter counterfeiting.
Print Process
Dry-offset printing, also known as indirect letterpress or offset letterpress, is a printing process that combines elements of both offset and letterpress printing. It is commonly used for printing on three-dimensionnal objects, such as metal and plastic containers, and is particularly well-suited for items like cans, cups, and tubes.
Plate Making:
Similar to offset printing, dry-offset printing uses polymer metal backed plates. However, in dry-offset, the plates are not inked directly. Instead, the image is transferred from the plate to an intermediary surface called a blanket.
Blanket Cylinder:
The plate is mounted onto a plate cylinder. As the plate cylinder rotates, it comes into contact with a rubber blanket cylinder. The blanket is slightly flexible, allowing it to conform to the shape of the printing substrate.
Inking System:
The inking system in dry-offset printing is unique. It typically involves a series of ink rollers that apply ink to the surface of a metal roll called the ink fountain. The ink fountain transfers the ink to a series of rollers called form rollers.
Image Transfer to Blanket:
As the plate cylinder rotates and the plate comes into contact with the blanket cylinder, the inked image on the plate is transferred to the blanket. The blanket, being flexible, allows for the transfer of the image onto substrates with irregular surfaces. Different types of presses will use one colour per blanket, or multicolor per blanket, the number of blankets relating to the number of printing units (see Repro for Dry Offset course)
Substrate Contact:
The substrate, which can be a three-dimensional object such as a metal can or plastic container, comes into contact with the blanket cylinder. The blanket transfers the inked image onto the substrate.
Drying:
After the ink is transferred to the substrate, the printed material typically goes through a drying process to set the ink. Drying can involve the use of heat or other drying methods.
Repeat for Multiple Colours:
Dry-offset presses often have multiple printing units, each with its own plate and blanket cylinders. The substrate passes through each unit in sequence, allowing for the application of different ink colours layer by layer.
Different types of presses will use one colour per blanket, or multicolour per blanket, the number of blankets relating to the number of printing units (see Repro for Dry Offset course). In that case the multicolour artwork is transferred onto the substrate in one pass, and then the curing/drying occurs.