As a company grows an owner may have moved from a labor position to a management position. Gone are the days when screens were prepared correctly. Owner’s look around the shop as they grow and replace themselves with the highest qualified candidates available. In today’s tough economy it is rare to hire highly qualified screen makers and production management personnel, rather those positions go to recently hired workers who have taught themselves enough about the job to accomplish the tasks. However, as we will see, many techniques and ‘best’ practices disappear when job positions change within a shop. Often it’s the lack of training that runs the shop. I get the call: “I’ve got some bad emulsion here, it’s falling off the screen.” A conversation begins, starting at screen making 101, and then progressing to product knowledge. Too often the screen maker was promoted from screen reclaiming and before that he may have been a screen washer. In my shop if you could deal with cleaning plastisol screens for 30 days you passed the test and became a candidate for a better job, often assisting screen reclaiming, or development. As the worker progresses he may get to coat screens, then shoot them when the shop gets real busy. His training may have been minimal. The screens look the same as any others but too often the screen room develops habits that lead to poor performance on press.
How old is the bulb? Most untrained workers don’t know. With new workers it may never dawn on them that the bulb has lost its’ strength long ago. It still works, lots of white light but very little UV light that creates strong screens. This lamp may work for plastisol prints, but will breakdown with discharge inks.
• Exposure Lamp Integrator – A lot of shops don’t even know their exposure lamp has one. They shoot in seconds and never realize changing to units activates the integrator. On some exposure systems changing from units to seconds requires hitting just one button. New workers have no idea on the difference. Units measures light in lumens, and seconds measures time only.
1. Moisture Meter – a great tool to measure screen moisture to determine if your screen is completely dry. Touching the screen to feel if it is dry does not work.
2. Thickness Gauge – Measures the thickness of the mesh first, then the emulsion thickness, and then shows difference between the two.
If there is no difference, or 0% EOM then the thickness of the mesh and emulsion are the same, where the knuckles of the mesh are not covered with emulsion. Typically a 110-T’s fabric thickness is 134 microns, (found in our catalog at: www.murakamiscreen.com). So if we want 7-10% EOM for a strong screen to print discharge we will need the emulsion and fabric thickness to be 143 microns (7%), which is generally achieved with a 1:1 coat using the dull side of a scoop coater when using Aquasol HV or HVP, the best choice for water base or discharge inks.
3. Hand Held Microscope with stand – Allows excellent viewing of halftones, emulsion edges, to evaluate the exposure process. Allows skilled employees to show trainees sharp emulsion shoulders, crisp halfones, and vertical emulsion side walls to understand what to look for.
4. Exposure Calculators or Instructions to run a step test – Why? Because it uses your film or vellum. A calculator will be very accurate if you use a 5kw lamp and have a D-max in your image of 3.0+.
Murakami Emulsion is designed to be completely exposed and hold all the detail in the art. A lot of workers think that underexposing will create better details. This will create premature screen breakdown, rejects, and poor profit margins. When the screen is wet in development take some white cloth or a paper towel and wipe the inside of the screen in the exposed area, not the image. If there is slime, or emulsion color on the rag the screen is underexposed. With Murakami emulsion it is completely cured when no slime, no color transfer occurs and details are all present. Again a step test can determine the proper exposure time to determine these conditions. Here are some recommendations on emulsion selections for textile printing:
- Aquasol HV or HVP – Plastisol, Waterbase* and Discharge* king. That’s a typo, should be KING. This emulsion provides the best universal stencil for all textile inks.
- Photocure BLU or TXR – Very easy to use. Better for printers who only have a fluorescent tube system as it coats a little thinner and exposes better on weaker exposure systems.
- Photocure PRO – Excellent for halftone printing in textiles or graphics. Can print waterbase and discharge when hardened*.