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How to Coat a Screen with Emulsion

Posted by Mary Yaeger on 9/18/2017

Also seen on Printwear 




Coating a screen is also referred to as “making a stencil”. The process is done with emulsion which is a thick liquid that is sensitive to UV light. When you place artwork on the photo sensitive emulsion and expose it, a negative stencil is created. This negative stencil is what allows the ink to be printed on a garment.


Before we get into coating a screen we need to discuss the different types of emulsions that are available. There are three types of emulsion and capillary film – which could be used as an alternative to coating the screen. All emulsions work with plastisol inksWater based inks will eat through most emulsions so you will use an emulsion formulated to work best for water based printing.


Diazo Emulsion


Diazo emulsions have been used for many decades and are still preferred when low production cost is a major consideration. Diazo emulsions are either water resistant or resistant to UV and solvent-based inks. Plastisol inks may be used with either diazo emulsion type.


Dual Cure Emulsion


Diazo-Photopolymer emulsions, also known as dual-cure emulsions, offer the largest variety of features and applications. Dual cure photo-stencil systems provide remarkable image quality and exceptionally durable stencils. These are premium emulsions for use with UV, plastisol, water-based, and solvent-based inks. Whether you need an emulsion with high chemical resistance or one specifically for ceramic inks, our selection provides the right emulsion for your requirements.


Pure Photopolymer Emulsion


Photopolymer emulsions are one-component emulsion systems that are pre-sensitized and ready for use. They offer very fast exposure speed and can be used universally, but often are developed for specific applications and exposure equipment such as direct projection, high emulsion over mesh ratio or for coarse mesh counts. Photopolymer emulsions are typically resistant to UV, solvent-based and Plastisol inks.


Capillary Film


Capillary film can replace liquid emulsion as the technology necessary to meet a wide range of decorator demands, including textured garments, textured prints, and higher resolution images at a lower production cost. Capillary film is not messy like liquid emulsion, does not require mixing ingredients, does not require storage in the refrigerator, and has a longer shelf life. There is no waste, since you cut off and use just what you want.


Application


Emulsionscoop coaters are a must-have tool for coating screens with all direct liquid emulsions. Emulsion scoop coaters are the perfect way to get a smooth, even emulsion layer on your screen.  Simply pour an appropriate amount of emulsion into the coater reservoir then position the coater against the screen and move slowly and smoothly from the bottom to the top, adjusting the angle of the coater slightly as you go to ensure good coverage.  


It is usually best to get an emulsion scoop coater about 2-3 inches narrower than the inside screen frame width. You want the coater to be just wide enough to cover the entire emulsion width in one pass. For heavier ink deposits or to increase the durability of the screen for longer runs additional coatings may desired after the 1st application dries. This will provide a thicker more durable stencil. 


Now, you are going to start with a screen that has been degreased and dried without being contaminated with dust, lint or finger prints. Next, you are going to fill the scoop coater with emulsion. Place the screen frame in an upright position and secure it in place. Use two hands to hold the scoop coater.


When coating screens the emulsion needs to be even on the mesh. Thick and thin places will cause problems during drying and exposing. The thin places will expose faster and cause the image to not wash out due to over exposure. The thick places will expose slower and cause the image to break down and wash out.


There are three types of coating methods:


1&1 Coat – Apply one coat of emulsion on the print side, rotate the screen 180, and apply on the squeegee side. Dry in a horizontal position.


2&2 Coat – Coat twice on the print side, then twice on the squeegee side. After each coat, rotate the screen 180. Dry the screen print side down. This will require a longer dry time, longer exposure time and yield a thicker stencil. This coating method is great for athletic printing.


3&3 Coat – Start by using method 2 above. After complete drying of the emulsion in method 2, add an additional coat on the print side and dry again. This method produces the sharpest edges and thickest stencil and ink deposit.



After coating the screens, let them sit overnight to dry. Screens need to be dry to the touch before exposing.

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