Screen Printing: How Mesh Count Sets the Ink Film

Screen printing pushes ink through a woven mesh with a rubber blade. Everything that decides how much ink lands on the sheet is set before the job starts: the thread count of the mesh, the thickness of the emulsion on it, and the hardness of the squeegee. Change the mesh and the same artwork prints as a thin tint or as a raised patch of colour.

The stencil

A screen starts as a frame stretched with woven polyester or steel mesh. The mesh is coated with a light-sensitive emulsion, dried, and exposed through a film positive. The exposed emulsion hardens; the unexposed area washes out and leaves an open window in the shape of the image. Ink can only pass where the mesh is open.

Mesh count

Mesh count is the number of threads per inch. A 110 mesh has coarse openings and passes a heavy ink film. A 305 mesh has fine openings and lays down a thin film. The count sets the practical limits of the stencil: a fine halftone dot needs a high count, because a low count cannot hold a small opening in the emulsion, and a white cover on a dark shirt needs a low count, because the pigment has to sit on top of the fabric.

The thread diameter matters as much as the count. Two screens with the same count can have different open area if one uses a thinner thread. Open area is what the ink actually passes through, and it is the number that decides the film thickness.

Emulsion thickness

The emulsion is not only a stencil, it is a measured layer. A coater with a defined edge lays a wet film of a known thickness, and the dried coat becomes the depth of the ink well. A thick coat on a low mesh holds a heavy deposit for a graphic print. A thin coat on a high mesh gives a sharp edge and a flat film for four-colour work.

The squeegee

The squeegee pushes ink across the screen and shears it through the open mesh. A hard blade (70 to 80 shore) leaves a thin, sharp film. A soft blade (60 to 65) bends into the mesh and deposits more ink. The angle matters: a steeper angle drives ink through with less deposit, a flatter angle leaves more. Speed matters as well, because fast stroke shear-thins the ink and gives a thinner film.

Off contact

The screen does not sit flat on the substrate during the print. It is held a few millimetres above, so the mesh snaps away after the squeegee passes. That snap-off is what gives screen printing its clean edge. Too little off contact and the screen stays glued to the ink, which smears the image and distorts the stencil. Too much and the mesh stretches, which changes register.

Ink

Screen ink is thick, and its viscosity falls as the squeegee shears it. That behaviour is what lets it pass a fine mesh and then hold a shape on the sheet. A plastisol stays where it is printed and is fused by heat. A water-based ink soaks into the fibre and dries by evaporation. A UV ink cures in a fraction of a second under a lamp and can be printed wet on wet.

Where the process fits

Screen printing lays a heavier film than offset or flexo. That is why it is used for garment prints, decals, signage, glass and plastic containers, and for spot colours that have to be opaque on a dark background. The heavy film also means the process is slower and the setup is longer, because every colour needs its own screen and its own registration.

The check

A printer can read the result with a micrometer on the dried film, or by weighing a printed panel against an unprinted one. Visually, the check is the edge: a clean edge with no sawtooth means the mesh and the emulsion were matched to the artwork. A ragged edge or a filled-in dot means the mesh was too coarse for the detail. Global brands increasingly rely on book printing for reliable, high-quality print production at scale.