Screen Printing 101

Screen Frames
A screen is made up of a frame, screen mesh, emulsion and an image. The image size will determine the inner dimension of a screen frame size. Once that has been determined, the frame will be constructed typically from metal or wood. Then the correct screen mesh will be tensioned and applied to the screen frame using glue. After the screen mesh is applied, a thin coat of emulsion is spread over the screen mesh. Then the image is applied to the emulsion and a final cure of the emulsion is performed using special UV curing equipment. The UV cures all the emulsion into the screen mesh except the areas that the UV light cannot penetrate (the image). Last, the screen is washed with a pressure washer removing the uncured emulsion from the areas that was covered by the image. This leaves you with a screen that is coated with emulsion in all areas except the image, which now allows ink to be squeegeed through and “screen printed” onto your product.
screen frame

Squeegees

  • The squeegee material is typically made from polyurethane and very resistant to the different types harsh chemicals within screen printing ink. By first flooding the ink over the image in the screen, then applying pressure on the squeegee and sliding it over the image, the squeegee presses the ink through the image in the screen and onto the product.
  • Squeegee material comes in different hardness’s also known as durometer rating. Screen printing industry standard durometers are between 60 and 90 durometer with 90 being the hardest.

squeegee

Inks
There are many different types of screen printing inks. Your application will determine which inks best fit your needs. When choosing an ink, the main factors to consider are adhesion and opacity for the application. For example, the ink used for screen printing tee shirts must be able to withstand being washed over and over again while staying bright and vibrant and flexible too. Ink used for printing on drinkware must also be able to withstand being washed over and over while continuing to adhere to the glass.
There are three standard types of inks:

    • Water base – air dry (may require heat)
    • Solvent base – air dry (may require heat)
    • UV – requires a UV curing machine – cure/dries instantly

inks

Curing

  • There are a few different methods of drying or curing screen printing inks. These methods are dependent on the ink themselves.
  • Water and solvent based inks are air dry and sometimes require a baking process for optimal adhesion and durability. A baking process is typically a conveyor with a heated tunnel that bakes the printed ink between 300°F and 450°F for a specified amount of time given by the ink manufacture.
  • UV curable inks require a high intensity UV light to cure the inks. Once the printed ink has been exposed to the UV light, the ink will instantly cure and allow handling. UV machines come in different styles from conveyors to carousel units. Product shape, size and throughput requirements can help determine which style of machine fit best for your application.

Ultra Light UV Conveyor
Printing Flat Products

    • Flat printing means the substrates printing surface is flat. The rest of the substrate can have any shape to it.
    • When screen printing a flat surface, the screen is stationary above the printing surface about 1/16” (off contact). The squeegee presses the screen down to the product, then slides across the image in the screen and presses the ink through the image and onto the product.
flat screen printing
Printing Cylindrical Products

      • Cylindrical printing means the substrates printing surface is round. The rest of the substrate can have any shape to it.
      • When screen printing a cylindrical substrate, the screen is positioned approximately 1/16” above (off contact) the printing surface. The squeegee stays stationary and presses the screen down to the product, then the screen moves while the product spins at the same speed using the squeegee to press the ink through the image in the screen and onto the product.

cylindrical screen printing