The ability to print any design onto apparel hinges on the quality of the screen and the image it carries. Despite its pivotal role, screen making is often an overlooked and underappreciated step in screen printing. This could be due to the messy, hands-on nature of the process or the technical complexity that intimidates some. More likely, it’s a combination of these factors, coupled with a lack of recognition for how critical this step is to achieving high-quality prints.
At its core, screen making is straightforward: apply a light-sensitive emulsion to a mesh, create a positive image, and expose them together to form a stencil. However, the devil is in the details, and it’s these small, often ignored aspects that distinguish an exceptional screen from a subpar one.
The Screen’s Dual Role
A screen serves two fundamental purposes:
- It holds the image to be printed.
- It regulates the amount of ink that passes through to the substrate.
The precision with which the screen reproduces the image and controls ink flow is where the Ttechnical challenges arise. Key factors influencing this include:
- The stencil’s ability to capture fine details.
- The mesh’s capacity to support those details without clogging or losing adhesion.
Even if the image is perfectly replicated, the ink deposit’s quality is critical. For process-color printing, where inks are transparent, precise control over ink thickness is essential for consistent color reproduction. Poor ink control leads to color variations, undermining the design’s integrity. Similarly, when printing opaque inks on dark fabrics, excessive ink or pressure can push ink through the garment, resulting in a weak print with poor coverage and a stiff texture. Properly managed screen characteristics can prevent these issues.
Consistency is Key
Producing a great screen occasionally is achievable, but the real challenge lies in consistently creating high-quality screens. Inconsistent screen making leads to unreliable results, making it impossible to deliver repeatable work to clients. This alone underscores the need to master screen making.
To truly understand screen and stencil quality, magnification tools are invaluable. We offer an Egg-Cup 8x Magnifier, a Folding 6x Magnifier, and a 10x Illuminated Magnifer. These magnification tools will reveal details invisible to the naked eye and worth the investment.
Ensuring Screen and Stencil Durability
A screen and its stencil must withstand the entire print run. The coating, drying, and exposure processes significantly impact durability. The stencil must have enough emulsion to fully cover the mesh and encase its threads.
The emulsion type and coating method determine stencil thickness. Opt for a high-solids (40%–50%+) direct emulsion, where “solids” refers to the resin content remaining after water evaporates. Higher solids content results in a smoother, thicker, and more robust stencil. For textile printing, a round-edged scoop coater is ideal for applying emulsion.
Coating techniques vary based on mesh count and open area. Coarser meshes require more coats to achieve the proper stencil profile. For halftone screens with 305–355 mesh counts, a two-over-two method works well: two wet-on-wet coats on the print side, followed by two on the squeegee side, with the screen dried print-side down. This ensures a smooth, uniform printing surface as the emulsion settles.
Drying screens thoroughly is critical, ideally in a room with 35%–55% relative humidity (RH). Circulating dry air with fans and a dehumidifier is essential to remove moisture from the emulsion. Trapped moisture can cause stencil failure or poor image transfer from positives.
Exposure requires high-intensity ultraviolet (UV) light in the 365–390 nm range. Polyester positives require sufficient power to penetrate any background density, preventing underexposure.
Mesh Tension and Screen Dynamics
Mesh tension is a critical factor in screen performance. Higher tension reduces the fatigue cycle—the distance the screen stretches during printing—controlled by off-contact distance. For example, a 1/16-inch off-contact results in a 1/8-inch fatigue cycle, while a 1/4-inch off-contact doubles it to 1/2 inch. Excessive stretching, like repeatedly bending a paper clip, can cause mesh failure. High-tension screens minimize fatigue, allowing longer print runs without mesh degradation.
Consistent tension, typically 22–25 N/cm² or higher, is more important than absolute tension levels. The open area of the mesh affects achievable tension; thinner threads (e.g., S-diameter) have more open area but hold less tension than T- or HD-diameter threads. T-diameter threads are a reliable choice across mesh counts. As skills improve, gradually increase tension to 30–50 N/cm² for optimal results, reducing registration issues and screen distortion.
High-tension screens also combat cold flow, the natural stretching of polyester mesh over time. Retensionable screens allow adjustments to maintain stability, unlike rigid frames. High-modulus, low-elongation meshes further minimize cold flow, enhancing performance on retensionable frames.
Emulsion Options
Stencils can be made with direct emulsions, coated onto the mesh, or capillary films, applied to clean mesh. While capillary films offer excellent image quality, their higher cost leads many to favor direct emulsions.
Direct emulsions come in three types, defined by their sensitizers:
- Pure Diazo: Affordable but moisture-sensitive, requiring thorough drying to avoid weak stencils. They have medium-to-slow exposure times and a shelf life of 4–6 weeks after the sensitizer is mixed with the base, extended by refrigeration. Best results come with UV-rich light sources.
- Pure Photopolymer: Fast-exposing (10%–20% of diazo time) and moisture-resistant, ideal for humid environments or weaker light sources. They have a long shelf life and often come presensitized but are less effective for fine halftone details.
- Dual-Cure: A hybrid of diazo and photopolymer, offering excellent detail, moisture resistance, and durability. They’re ideal for most applications, especially fine halftones.
The stencil must bridge mesh openings and sit above the threads for smooth, sharp prints. Rough stencils produce jagged edges, especially on dark garments or fine halftones. Microscopic inspection helps evaluate stencil quality.
The Pursuit of Perfection
Screen making is both an art and a science. With modern materials and techniques, the potential for exceptional results is within reach. Success depends on skill, attention to detail, and a commitment to continuous improvement. By closely examining each step—emulsion, coating, drying, exposure, and tension—you can create screens that consistently deliver stunning, reliable prints, meeting and exceeding customer expectations.