THE BASICS OF COATING A SCREEN
Scoop Coater Essentials:
- Use a scoop coater with a sharp side for precise control or a round side for a thicker emulsion layer.
- The basic technique involves tilting the coater forward, making contact, applying emulsion, and then rotating the screen to coat the other side.
Common Problems:
- Inadequate pressure or proper contact can lead to uneven coatings.
- Avoid scraping too much, which thins the stencil. Aim for even pressure and contact.
THE GLISTEN METHOD
To confirm you've applied a good layer of emulsion, use the glisten method:
- Look for a slight reflection off a light source.
- Ensure both the t-shirt and squeegee sides of the screen have a glossy, even coat.
VARIABLES IN SCREEN COATING
Several factors influence the quality of your stencil:
- Solids Content: The percentage of solids in your emulsion affects its thickness after drying. Higher solids content means less shrinkage and a thicker stencil.
- Viscosity: Emulsion thickness varies. Thin emulsions flow easily; thicker ones need careful handling.
- Scoop Coater Sides: The round side deposits more emulsion than the sharp side. Adjust your technique based on your desired stencil thickness.
- Application Angle: The angle at which you hold the coater impacts the emulsion layer. A steep angle deposits less, while a shallow angle deposits more.
- Mesh Count: Different mesh counts require different emulsion quantities. Higher mesh counts need thinner layers (e.g., 1x1); lower mesh counts need thicker ones (e.g., 2x1 or 1x2).
UNDERSTANDING EMULSION OVER EMULSION (EOM)
EOM is the emulsion thickness ratio relative to the mesh count:
- Aim for 10-20% EOM, depending on your specific needs. Lower mesh counts typically want higher EOM around 20%, sometimes more.
- Use tools like an Electronic Thickness Gauge to measure the mesh and stencil thickness to calculate EOM accurately.
PRACTICAL TIPS
- Consistent Pressure: Apply even pressure when coating to avoid uneven stencils.
- Full Trough: A full trough of emulsion ensures a consistent application.
- Test and Adjust: Test different techniques and adjust based on your results. Keep notes on what works best for your specific setup.
FINAL THOUGHTS
Coating a screen is a skill that improves with practice and understanding. By considering the variables and using the right techniques, you can achieve perfect stencils every time.
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