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Choosing the right durometer for your squeegee blade in screen printing is crucial for achieving optimal print quality. The durometer refers to the hardness of the squeegee blade, which directly affects the amount of ink deposited onto the substrate, the sharpness of the print, and the overall consistency of the printing process. For my shop, we printed high detail and were aiming for the thinnest possible ink deposit and used an 85 durometer. But as in everything, each shop is different and you will need to decide what is best for your shop. Here's a detailed guide on how to choose the right durometer for your screen printing needs.
Understanding Durometer in Screen Printing
Durometer Measurement:
- Definition: Durometer is a standardized measurement of the hardness of elastomer materials, such as the rubber used in squeegee blades.
- Scale Used: The Shore A scale is commonly used for squeegee blades, with values typically ranging from 50A to 90A.
Common Durometer Ratings:
- Soft Blades (50A - 60A): These blades are more flexible and deposit a thicker layer of ink.
- Medium Blades (70A): The most commonly used hardness, offering a balance between flexibility and rigidity.
- Hard Blades (80A - 90A): These blades are more rigid and deposit a thinner layer of ink.
Factors to Consider When Choosing Durometer
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Type of Substrate (Printing Surface):
- Absorbency: Porous materials like textiles may require more ink, benefiting from softer blades.
- Texture: Smooth surfaces like glass or metal often require harder blades for precise ink deposition.
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Ink Type:
- Viscosity: Thicker inks (e.g., plastisol) may require softer blades to push the ink through the mesh effectively.
- Drying Properties: Inks that dry quickly may benefit from harder blades to minimize ink buildup on the screen.
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Mesh Count and Tension:
- Mesh Count: Higher mesh counts have smaller openings and may require harder blades to force ink through.
- Screen Tension: Properly tensioned screens can accommodate a wider range of durometers, but lower tension may necessitate a harder blade to compensate.
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Detail Level of the Design:
- Fine Details and Halftones: Harder blades help achieve sharper lines and finer details by depositing less ink.
- Solid Areas and Bold Colors: Softer blades can lay down more ink, enhancing the vibrancy of solid colors.
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Desired Ink Deposit:
- Thicker Ink Layers: For raised effects or vibrant colors on dark substrates, softer blades are preferable.
- Thinner Ink Layers: For a softer hand feel on garments or when overprinting, harder blades are ideal.
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Printing Speed and Pressure:
- Manual vs. Automatic Printing: Automatic presses often operate at higher speeds and may benefit from harder blades to maintain consistency.
- Operator Technique: The amount of pressure applied can affect ink deposition; adjusting durometer can help achieve desired results.
Types of Squeegee Blades
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Single Durometer Blades:
- Characteristics: Uniform hardness throughout the blade.
- Usage: Suitable for general printing needs where specific control over ink deposition is not critical.
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Dual Durometer Blades:
- Characteristics: Two layers of different hardness (e.g., 70A core with 90A outer layer).
- Usage: Provides a balance between flexibility and rigidity, maintaining a sharp edge under pressure.
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Triple Durometer Blades:
- Characteristics: Three layers, typically with a softer core sandwiched between harder outer layers (e.g., 90A/70A/90A).
- Usage: Offers the flexibility of a softer blade with the stability of a harder blade, ideal for high-speed automatic presses and detailed prints.
Guidelines for Choosing the Right Durometer
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For General Textile Printing:
- Recommended Durometer: 70A single durometer blade.
- Rationale: Provides a good balance for most fabric types and ink viscosities.
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For High-Detailed Prints:
- Recommended Durometer: 80A - 90A single or triple durometer blade.
- Rationale: Harder blades reduce ink deposit, enhancing detail and preventing ink spread.
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For Heavy Ink Deposits:
- Recommended Durometer: 50A - 60A single durometer blade.
- Rationale: Softer blades flex more, allowing more ink to pass through the mesh for vibrant colors on dark substrates.
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For Specialty Inks (e.g., Metallic, Glitter):
- Recommended Durometer: 60A - 70A single durometer blade.
- Rationale: These inks often have larger particles and higher viscosity, requiring a softer blade to transfer effectively.
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For Overprinting and Fine Halftones:
- Recommended Durometer: 80A single durometer or dual/triple durometer blade.
- Rationale: Minimizes additional ink deposit, maintaining the integrity of underlying layers and fine details.
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For Automatic Presses:
- Recommended Durometer: 70A - 90A dual or triple durometer blade.
- Rationale: Harder blades withstand the increased pressure and speed, maintaining a consistent print.
Additional Considerations
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Blade Edge Shape:
- Square Edge: Standard for most applications, providing consistent ink deposit.
- Rounded Edge: Deposits more ink, useful for heavy ink applications.
- Beveled Edge: Reduces ink deposit, suitable for fine details.
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Blade Maintenance:
- Regular Inspection: Check for nicks, wear, and solvent damage.
- Proper Cleaning: Use appropriate cleaning agents to prolong blade life.
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Environmental Factors:
- Temperature and Humidity: Can affect ink viscosity and blade performance; adjust durometer if necessary.
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Testing and Experimentation:
- Sample Prints: Conduct test prints with different durometers to determine the best outcome.
- Adjust Variables: Sometimes, a combination of adjustments (mesh count, squeegee angle, pressure) alongside durometer changes yields the best results.
Conclusion
Selecting the right durometer for your screen printing squeegee is a critical step that influences print quality, efficiency, and consistency. By considering factors such as substrate type, ink properties, mesh count, and design complexity, you can make an informed decision that enhances your printing results. Remember that experimentation and experience play significant roles in fine-tuning your process, so don't hesitate to test different durometers to find the perfect fit for your specific needs.
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