How to Print High Density Ink

Screen Printing ink

High density ink requires retensionable screens and capillary film.

The retensionable screens at very high tension will be dimensionally stable to hold registration when printing off-contact and release a deposit of ink that is uniformly thick.  An off-contact screen is critical for the mesh to “peel off” the ink deposit without picking ink out of the printed image. 

Capillary film is fundamentally different from liquid emulsion.  Liquid encapsulates the mesh.  Capillary film is a layer of stencil material under the mesh.  Ink passes around the threads of the mesh, and the image created is photographic quality without the interference of mesh.  Capillary film can also be applied in different thicknesses to create different, controlled, thicknesses of ink deposit.

To shear ink easily, the squeegee blade must be flat along the bottom edge, and have a square sharp edge.  The blade should be sharpened daily before being used.  A triple durometer like 75-92-75 will prevent flexing of the blade, or pushing excessive ink down into the ink well.  Excessive squeegee pressure can be easily avoided by using a squeegee blade with a free area to the handle of at least 1 ¼”.

Ink selection is critical to success.  All high density inks, regardless of color, must print exactly alike.  All the inks must be “short body,” i.e. shear easily.  Ink can be tested by stirring well in the manufacturer’s container and then drawing the stir stick straight out of the can.  “Short body” ink on the stick immediately separates from the ink in the container much like pudding or yogurt.  By contrast, an undesirable ink will stay connected to the stick like chewing gum.  Such inks are more difficult to shear.  Curable reducer is not a good solution for long body inks being printed in thick deposits.

When setting up a job, a shim, e.g. Plexiglass .06” thick, should be placed on the platen and the machine adjusted so the machine arm that supports the screen is resting on the off-contact bolt while the screen is on contact on the shim.  T-shirts are approximately .03” thick.  So when the shim is removed, T-shirts will be printed off-contact .03”  giving the mesh an opportunity to peel off.  Most important, the screen will be absolutely parallel to the shirt and deliver an ink deposit of uniform thickness.  Thicker materials like caps and fleece require a thicker shim.

A 50 micron stencil will leave ink on a T-shirt of sufficient opacity to eliminate the need to flash and print again.  100 microns will compensate for the texture of a pique or herringbone shirt, and yet leave the image soft and flexible.  Thicker stencils deliver the 3rd dimension to the image.

The mesh is typically coarse like 60 to allow ink to flow easily.  Ink flow can be controlled to facilitate resolution by using a 110 or even a 160 mesh.  The 110 is a recommended selection for T-shirts and golf shirts.  The 160 will prevent small details like the letters p, d, e, o and q from closing in. 

Textures separate screen printing from other types of printing, and high density ink is the key to printing textures.