EOM, or emulsion over mesh, is a measurement of the emulsion thickness compared to the mesh thickness. When the EOM is correct, it creates an excellent stencil which acts as a gasket for the ink to deposit onto the substrate. A heavy flood of ink will fill the gasket on the print side of the screen. Because of this, the ink is already through the mesh, allowing the squeegee to lay the ink onto the substrate with minimal pressure. The result is a smooth even print with the majority of the ink on top of the garment rather than through the garment. An obtainable goal for the EOM is 20 percent.
Source: Ray Smith