06 Jan Will Degreasing Eliminate Pinholes?
I am often asked about the true purpose of degreasing and if it will really eliminate pinholes. It seems that there are a number of individuals who, perhaps, on a budget-minded philosophy have eliminated degreasing entirely from their screenmaking process. Their thinking is that the ink and emulsion removing process has completely eliminated the need for degreasing.
Let’s begin with the fact that degreasing, alone, is not an anti-pinhole step, per se.
However, degreasing should be performed on all new mesh, since the manufacturer did not clean the mesh of any contaminants that might be on the mesh. Also, keep in mind that mesh can be contaminated during handling at the distribution point, in shipping, and at any point prior to coating the mesh with emulsion. And, degreasing is an important step to be performed just before the mesh is coated with emulsion. After degreasing, care should be taken that the mesh is not further contaminated by the use of fans, which might blow dust particles on the mesh. It is suggested that the screens be dried in a dust-free cabinet and once dry, be coated immediately.
In other words, degreasing is a necessary step to remove any oils or contaminants from the mesh threads that will cause the emulsion to not grab hold of the thread, or create issues will create extra work after developing. It is a benefit of the degreasing step that it can help to remove some other contaminants that are on the mesh that might cause pinholes.
However, pinholes (and fisheyes) are created by a number of things, including any contaminants left on the mesh prior to coating. Below is a shortlist of things that cause pinholes.
- Unclean screenmaking department creates the possibility of dust on the wet mesh and emulsion
- Any airborne contaminants can settle onto the mesh or emulsion
- Contaminates in the water system that are not filtered out can create pinholes
- Hard water will leave behind calcium that causes pinholes
- Chemical contaminants left on the mesh can be problematic
- Degreaser not thoroughly rinsed from mesh
- Oils from second-hand smoking
- Screens not coated as soon as they are completely dry are always subject to pinholes
- Fans in the screenmaking area that blow dust on the wet mesh or emulsion
- Contaminates in the emulsion
- Improperly prepared emulsion
- Improper scoop coater design
- Coating speed is too fast
- Emulsion moisture in excess of 4-6% during exposure
- Contaminates on the exposure unit glass
- And, yes, even too little exposure time