Modifying and adjusting plastisol ink is essential for achieving optimal print quality, print-ability and special effects in screen printing.
Because Plastisol ink is designed to be thick, opaque, and doesn’t dry until cured with heat, it offers flexibility but also requires careful preparation to handle specific print needs. Here are the most effective techniques for modifying and adjusting Plastisol ink to optimize results:
1. Adjusting Ink Viscosity
Plastisol ink is naturally thick, which works well for vibrant and opaque prints and helps the ink “stand up” on the garment. However, this thickness can be an issue when finer details or softer feels are required, or when printing either manually or on a press is problematic. Adjusting viscosity helps the ink flow more smoothly, reduces the risk of clogging fine screens, and will help you achieve optimum print results.
- Reducers: Adding a small amount of reducer (about 3-5%, by weight) can thin the ink, making it easier to pass through finer mesh screens and improving detail in the print. Common reducers include curable reducers, which don’t affect the curing process, and viscosity reducers, which provide smoother printing for intricate designs. Be careful not to add too much, as it can compromise opacity.
- Mix thoroughly: Whenever adding a reducer, mix thoroughly to maintain consistent viscosity throughout the ink. Otherwise, the consistency will vary and affect print quality.
2. Adding Extenders for Transparent Effects
Extenders can be added to Plastisol inks to create more transparent or muted colors, which is useful when creating a softer feel and/or for subtle color variations.
- Soft-hand clear extender: Adding a soft-hand extender to the ink will reduce opacity and create a lighter print with a softer feel on the fabric.
- Balanced reducer: A clear balanced reducer can also be used to reduce viscosity, lighten and extend ink colors while reducing the ink’s tackiness, making it more suitable for blending and layering effects.
3. Modifying for Opacity and Coverage
When you need high-opacity prints, especially on darker fabrics, you must be careful when modifying the ink - thick, sticky inks often ‘stand-up' on the fabric better.
- Add high-opacity pigments: If the ink is too transparent, adding high-opacity pigments or using a higher-opacity version of the color can improve coverage on dark garments.
- Thicker screens and lower mesh counts: Using a screen with a lower mesh count can help deposit more ink onto the garment, improving opacity. Adjusting the mesh count is an effective way to modify ink coverage without changing the ink formula.
4. Adjusting Ink for Soft-Hand and Stretchable Finishes
For fabrics that need a softer feel or require flexibility, such as athletic wear, modifying the ink for better stretchability and a softer feel is essential.
- Stretch additive: Adding a stretch additive to Plastisol ink improves flexibility, making it better suited for athletic fabrics or garments that need to stretch, like Lycra or spandex. This prevents cracking and preserves the design over time.
- Soft-hand additive: If the ink feels too plasticky, a soft-hand additive can make the final print feel softer. This is helpful for prints on thinner or more delicate fabrics like lightweight cotton.
5. Using Puff Additives for a Raised Effect
Adding puff additives to Plastisol ink can create a raised, textured effect that adds dimension to the print. This is often used for special designs or unique visual effects.
- Puff additives: Adding a puff additive to the ink makes it expand slightly when cured, resulting in a raised, three-dimensional print. This works well for certain design elements like logos, text, or graphic borders.
- Adjust curing: Puff inks require careful curing; they must be heated just right to achieve the desired puff effect without over-expanding or cracking. Test the curing temperature and time before running a full print job.
6. Color Matching and Custom Blending
Color consistency is vital in screen printing, especially for large orders or brand-specific designs. Adjusting ink colors to achieve perfect matches requires skill and a controlled ink room environment.
- Pantone color matching: The best way to achieve exact color matches is by using Pantone guides and pre-mixed colors that use the Guide. Many screen printers use color-mixing systems with precise ratios to match colors accurately.
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Custom blending: By blending base colors in measured amounts, you can create custom shades. Use a gram scale to ensure accuracy, document each mix, and test the color before full-scale production. This is especially important for repeat orders where color consistency is key.
7. Controlling Curing Temperature and Time
Curing is the final and most crucial step for Plastisol inks, as it determines the durability of the print. Adjusting curing parameters helps avoid issues like under-curing, over-curing, and ink bleeding.
- Heat gun or infrared puck or Thermo-Tels?: There is no doubt, Thermo-Tels are the most accurate and reliable! Use a heat gun to check the I.R. Panel to see if it is working, but it is only “ok”‘ for checking the curing temperature. Plastisol ink requires a curing temperature between 280°F and 330°F for proper bonding to the fabric.
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Test-cure samples: Before running a large batch, test-cure a sample to make sure the ink cures correctly without any smudging or under-curing, which can affect wash durability and color brightness.
8. Using Retarders for Extended Open Time
Plastisol ink doesn’t dry on the screen like water-based inks, which is an advantage in slower-paced or detailed jobs. However, in warm conditions or for extended runs, adding a retarder can help maintain optimal ink performance when flash curing.
- Retarder additives: Using a retarder in warm environments can keep the ink from thickening or drying out on the screen. This is particularly helpful for detailed prints that require flashing.
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Small amounts: Add a retarder sparingly, as too much can affect the curing process.
9. Regular Ink Maintenance and Storage
Proper storage and maintenance keep Plastisol ink in optimal condition, allowing you to avoid issues related to thickening or color inconsistency.
- Storage conditions: Keep Plastisol ink in a cool, dry place to maintain viscosity and color consistency. Extreme temperatures can cause thickening, separation, or uneven curing.
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Stirring and mixing: Regularly stir the ink to prevent pigment separation and ensure a consistent mixture. This is especially important for inks with additives or custom blends.
Always stir ink thoroughly before use in production. This breaks the “false body” that occurs in the bucket and provides for a more creamy and easy to print ink.
Summary
Mastering Plastisol ink modification techniques is essential for creating high-quality, versatile prints. Adjusting viscosity, adding extenders, and using additives enable screen printers to customize ink to meet specific design and print requirements. With precise ink adjustments, screen printers can ensure their work is durable, visually striking, and meets customer expectations for quality and longevity. By maintaining consistent color matching, properly curing each print, and preserving ink quality through careful storage and stirring before use, printers can maximize the effectiveness and longevity of plastisol inks.
