What are the differences among offset printing, intaglio printing, screen printing and flexographic printing?
The fundamental differences among the four types of printing: the way ink is transferred.
Offset printing (offset lithography)
Plate structure: Flat ink layer thickness: 1-2 um Ink viscosity: High Core principle: Oil and water do not mix
Due to the extremely thin ink layer, the granular aluminum silver paste will disrupt the precise ink-water balance, easily causing printing failures.
Therefore, the aluminum paste cannot be used.
Ink characteristics
Viscosity: High viscosity, low fluidity, ensuring uniform ink transfer. Drying: Dries by oxidation film formation, suitable for multi-color offset printing.
Ink layer: Extremely thin (1-2 um), resulting in vivid colors and rich, fine gradations on the printed product.
Requirements for aluminum pigments
The pigment particles must be extremely fine; otherwise, they are prone to scratching the printing plate or causing dirty or smeared plates during the printing process, seriously affecting the quality of the final product.
Gravure printing
Plate structure: Concave recessed ink layer thickness: 4 – 8 um Ink viscosity: Low Core principle: Ink storage in recesses, ink scraping by scraper
Ink characteristics
Viscosity: Thin, low viscosity (15-25 seconds for the SP-4 cup), good fluidity to fill the mesh holes. · Drying: Quick drying, rapid solvent evaporation, suitable for high-speed printing rhythm. · Ink layer: Thickness up to 4-8 um, strong covering power, more vibrant colors.
Core challenge: “Re-dissolvability” of water-based intaglio silver paste
Risk: If the aluminum-silver paste cannot be re-dissolved by the new ink after drying in the mesh holes, it is very likely to cause “plate blockage”, resulting in the interruption of the entire production line. · Key indicators: The particle size of the aluminum-silver paste needs to be strictly controlled within 10-15 um, and the coating layer must have excellent re-dissolvability.
Flexographic Printing
Plate Structure: Raised Graphic and Text Ink Layer Thickness: 2 – 5 um Ink Viscosity: Low Core Principle: Ink Transfer by Mesh Roller, Light Pressure Transfer
Ink performance characteristics:
Viscosity: Low viscosity formulation ensures high fluidity to meet the requirements of high-speed printing.
Type: Mainly uses environmentally friendly water-based ink, and UV ink with fast curing speed is adopted in some scenarios.
Ink layer: The thickness of the ink layer is approximately 2-5 um, which is between the thick ink layer of intaglio printing and the thin ink layer of flat printing, balancing coverage and delicacy.
Core challenge: “Low foaming” of water-based flexographic aluminum silver paste
Key risk: If foam is generated during high-speed printing, it is very likely to cause white spots or pinholes on the printed surface, directly resulting in batch waste. Technical indicators: Strictly control particle size, requiring D9O < 15 um, and the particles need to be round and smooth to avoid scratching the expensive screen pattern plates due to sharp particles.
Screen printing
Plate structure: Meshed blank area ink layer thickness: 10 – 100 um Ink viscosity: Extremely high (paste-like) Core principle: Scrape plate extrusion screen printing
Ink characteristics: Thick paste-like ink layer
Strong three-dimensional appearance with high thixotropic property (thick when stationary / thin when scraped): The ink layer thickness ranges from 10 to 100 micrometers, being the thickest among all printing processes. The pattern has an extremely strong three-dimensional effect. It has a “high tolerance” brilliant effect on pigments. The maximum allowable pigment particle size is up to 50 micrometers, making it the process with the highest tolerance. It is highly suitable for adding large particle size metallic aluminum silver paste to achieve a highly visually impactful core. Core challenges: Risk of clogged mesh: Solvent evaporation too fast – ink drying – mesh blockage. Solution: Select solvents with moderate evaporation speed or add slow-drying additives.
- Practical selection: A simple and effective testing method. Core strategy for intaglio water-based silver paste: Opt for the “re-dissolution type” coating process.
Testing method: Add the silver paste to the varnish and apply it as a film. After 5 minutes, wipe it off. If it cannot be wiped off = poor re-dissolution = return directly. - Flexographic water-based silver paste
Basic indicators: Particle size D90 < 15um, and the dynamic surface tension must remain stable. Testing method: Stir evenly and then let it stand for 1 minute.
The foam height should be less than 1cm to be considered qualified. - Screen printing water-based silver paste
· Product selection: It is recommended to use “sparkle type” aluminum silver paste with a larger sheet diameter to achieve better coverage and metallic texture. Note: It is not suitable for water-based high-speed printing, and attention should be paid to preventing the screen from drying.
The water-based aluminum silver paste produced by Shandong Jiehan not only has excellent covering power but also presents a very good metallic effect. Please feel free to request samples for testing.