Screen E-Book (.PDF) - MacDermid Autotype

The wrong way: a strong-deep flood.I could finish there. It’s so easy that reallyyou could go straight on to step 2.But I’ve had hour-long arguments withprinters who think that flooding should bestrong and deep, getting the ink right to thebottom of the stencil so that the squeegeecan … Well. They are 100% wrong.Think about it. If your flooding gets close tothe bottom of the stencil, then you’re closeto going beyond the bottom of the stencil.You’re therefore going to have ink stickingout beneath the stencil, and when thestencil contacts the substrate that ink willsquash out and give you a messy print.I’m happy for you to argue with me aboutthe phrase “the lightest possible”. I cansee your point. If the flood gets you, say, ¾the way down through the mesh/stencilthere’s less work for the squeegee to do instep 2.I have two arguments against you. The firstis a bit weak, the second is strong and a bitsubtle.Here’s the weak argument. If you reallyneed a strong flood, you probably havesomething else wrong in the system. Forexample, your stencil might be so thickthat you need large flood and squeegeeforces in order to print at all. Why wouldyou want to use a thick stencil? Becauseyou need a thick print. But then you aregoing against Golden Rule 1. You are usingthe stencil to control ink thickness, but therule says that the mesh should be doingthat. So, the need for a strong flood can bea symptom of something wrong in yoursystem.Here’s the strong argument. The flood bladeis pushing the liquid with relatively lowshear. This means that if you have ink that’sstarting to dry in to the mesh, the pushfrom the flood blade is unlikely to dislodgethe drying ink. As we’ll see, the squeegeestroke gives a strong shear force that canprovide a powerful cleansing action andhelp keep your mesh open. The first time Ithought of this argument I wasn’t sure if itwas right. But I said it anyway.11