This question comes up often with screenprinters: why can we not hold detail?
The answer is an idea similar to the art department concept of problems with source artwork where we say “garbage in, garbage out.” We are now are transferring that idea to print production. Basically, if you have a crappy stencil you have no chance of achieving high detail in print.
Some basic answers on the pre-press stencil end of things:
- Your exposure unit has too much light scatter. Either paint the inside black or get a better one. By the way I had a major manufacturer’s rep tell me that their all-in-one direct to screen and exposure unit had “no light scatter.” That’s a lie. Once they said that I could not believe anything they said. There is always light scatter, it is a matter of degree. Too much will eliminate your dots and fill in your detail.
- Too weak of an exposure lamp from it being crappy or from it being old. As per what I just said about light scatter, if your lamp takes too much time to expose the screen, it eventually will go around the details in the film. So get a better unit or replace your bulb. Check out Saati’s new LED point source light, very affordable and the light basically never goes bad.
- Your films/vellum are not dark enough. Basically the light then goes through the details and exposes the screen. We had someone recently ask us why they should upgrade to a film unit from their toner copier way of making films. This was the answer. You could see through the toner and if you can, then the light of your exposure unit will also go through it. Get a decent unit or change your settings. If you really can’t afford a better unit, get somebody else to make you some films for the difficult jobs. Most shops with bad printing or that struggle mightily to do their work have bad film/vellum at the start of their problems. Call up SPSI and get their advice and also buy ink and film from them to go with the EPSON printer they advise you to buy.
- Poor contact between film and screen. Make sure your vacuum frame is working correctly. If there is poor contact the light can go around the dots and fine lines. All blankets are not equal. Talk to Douthitt if you need a good blanket. Another answer to this is to use a Direct to Screen unit, both KIWO and Douthitt make good ones and more importantly support and service them.
- Bad emulsion. Make sure you have a good emulsion for holding detail and will work with the mesh count you are using. A quick exposing emulsion or one with a wide latitude of exposure can help make up for a lousy exposure unit. Good emulsion has good resolution and good bridging between the threads. KIWO and Saati make great emulsions and give honest advice. Don’t try to save money on emulsion, that is penny wise and pound foolish, i.e. dumb.
- Wrong mesh count. With the right emulsion you can hold more detail on lower mesh counts, but generally you need to use finer and finer mesh to hold finer and finer detail. And make sure the mesh you are using is what you think it is. Keep your screen well marked as to what most they are.
- Good screen tension. If you have lousy tension you will not consistently hold detail. Either get newman roller frames and keep them tensioned with good mesh, or get rigid aluminum screens from a good place like GSF. If you use rigid frames then make sure when the tension gets too low that you get them restretched by a good place like GSF or buy a very good stretcher yourself from Saati. Crappy screens will give you crappy prints, including not holding detail well.
- Good art. Make sure that the artwork is crisp in the first place and that the details are really there.
- Be reasonable. Make sure the details you are trying to hold are possible to hold. Don’t try to print an entire face that is 3 millimeters in diameter. Either say you can’t do it or enlarge the art.
Ok, now your films and screens are good. Why do you still have crappy reproduction on details:
Prepress is only part of the issue and probably the smaller part these days The reality is that now creating a decent to good quality stencil is not the huge challenge it once was. With the proliferation of CTS technology (or at least inexpensive epson film printers replacing vellum) and dramatic improvements to emulsions, mesh, light sources, it much easier to get your pre-press correct.
In our own shops and observing many other shops, the biggest issue we see in achieving a high level of detail in print is and always will be proper press settings. By that we mean appropriate:
– squeegee and flood pressure, angle, speed