Understanding Emulsion Over Mesh (EOM) | Deep Dive With Colin

Welcome back to another Deep Dive with Colin! This topic will be focused on a fundamental aspect of screen printing: coating a screen to get a perfect stencil. This is packed with insights and tips for both beginners and seasoned printers. Whether you're just starting or have been in the business for years, you'll find valuable information here. Watch the video below for a detailed demonstration and read on for a comprehensive guide!

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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