ScreenPrint
  1. First, I established that he was using very tight screens. He said he was using roller frames (and had for a long time) and that he had a tension meter and worked hard to hold a minimum of 25 newtons. That was the right answer.
  2. I asked how he was coating his screen. He gave the right answer. He was using a direct emulsion and using the sharp edge of the coater. He coated the underside once followed by the inside once.  A good start. I recommended on the underbase screen to give it a second coat on the bottom – after the first coat was dry.
  3. I asked how good his films were. He said he was using a software RIP (for halftones and to lay down more ink) and was printing to an Epson 1400 printer (Epson uses similar but different model numbers in different countries). This printer uses dye based ink. That’s a good thing.  He swore his films were very dense.
  4. I asked what brand of emulsion he was using. He said it was a one-part. That tells me he is using a pure photopolymer emulsion that has a long shelf life. It sounds great but the fact is these emulsions are very fast and don’t have the latitude of exposure times a two part emulsion has.  Obviously – his supplier recommended this. I would have recommended a two-part “dual cure” emulsion. They are forgiving, fairly fast, and easy to use. They have a three month shelf life when mixed.
  5. He was using 305 mesh (120 in cm) mesh for all the colors per my directions. I asked how long he was exposing and what his light source was. He was using a 1000 watt mercury vapor bulb in a professional unit with a vacuum blanket. Good. He said he burned his everyday 125 mesh  (49 in cm) mesh for two minutes AND HIS SUPPLIER SAID TO GO LONGER FOR HIGHER MESH so he was going four minutes for the 305 mesh!  Wow. I about fell off my chair. You never go longer for higher mesh. The longer you go the more the exposure light burns around the dots AND the emulsion coating is MUCH thinner on a thinner screen mesh. No wonder he could not hold the dots on the screen.
  6. I asked him what his halftone frequency (LPI) was and what angle and dot shape he was using. He said he used my recommendations of 55LPI at 25 degrees with a dot shape of ellipse.  Good call! The right answer.
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    Scott Fresener

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