Screen printing on uneven surfaces, like garments with seams or pockets, requires specific techniques to ensure print quality.
Printing on items with varying thicknesses or textures presents unique challenges compared to flat surfaces. The ink needs to deposit evenly across areas that are raised or depressed relative to the main printing plane.
One effective method for screen printing over bumps, seams, or pockets, especially in apparel decoration, is to modify the printing platen itself.
Advanced Platen Preparation
A key technique mentioned in industry practices involves altering the platen surface to better accommodate the unevenness of the substrate.
- Using Adhesive Neoprene Sheeting: An advanced technique for achieving high-quality prints over seams and pockets involves using adhesive neoprene sheeting to cover the platen.
- How it Works: This creates a softer, slightly yielding surface on the platen. When the uneven garment (like a t-shirt with a thick seam) is placed on top, the softer neoprene allows the platen to compress slightly under the pressure of the screen and squeegee around the raised areas. This helps the screen make better contact with the surface around the seam or pocket, compensating for the height difference and allowing for more consistent ink deposition.
Other Considerations for Uneven Surfaces
While modifying the platen is crucial, other factors also play a role in successful printing on uneven items:
- Off-Contact: Adjusting the off-contact (the space between the screen and the substrate) is vital. Too little off-contact can cause the screen to stick to the ink, especially over high points. Slightly increasing off-contact can help, but too much can distort the image. This needs careful balancing.
- Ink Type and Viscosity: Using inks with appropriate viscosity can help. Thicker inks might not flow well over uneven areas, while thinner inks might bleed. Plastisol inks are common for apparel and can often bridge minor gaps, but technique is still key.
- Mesh Count: Sometimes, using a lower mesh count screen can help deposit more ink, which might slightly fill in low spots, but this is less about handling the unevenness itself and more about ensuring enough ink transfer where contact is good.
- Print Pressure: Consistent and appropriate squeegee pressure is essential. Too much pressure can push ink under edges, while too little won't transfer ink properly, especially around difficult areas.
- Print Stroke: The angle and speed of the squeegee stroke can influence ink transfer over uneven surfaces.
Combining platen modification with careful adjustments to off-contact, pressure, and potentially ink properties provides the best chance for success when screen printing challenging items like finished garments with seams, zippers, or pockets.
