Screen prep is where print quality gets decided long before a screen ever hits the press. Coating, drying, and exposing screens correctly takes more attention to detail than running the press itself, and small inconsistencies here show up later as pinholes, breakdown, or registration issues on the job. So what does a screen prep process look like that holds up under daily production, from environment to exposure? Grimco supplies the emulsions, coating tools, and screen printing chemicals to build that process, including our exclusive Rise Screen Solutions emulsion line.
- Setting Up Your Screen Room
- Choosing a Coating Trough
- Clean Screens With Good Tension
- Choosing a Reliable Emulsion
- Proper Coating Technique
- Standardizing the Process
1. Setting Up Your Screen Room
- Separate – Coat, dry, and store coated screens in a room away from the washout booths.
- Clean – Dust is the enemy, and it will show up on your screens. Shirts are linty, so wipe, mop, and clean your screen room regularly.
- Filtered Airflow – Filter the air coming into the screen room. You need airflow to remove moisture unless you're running a dehumidifier. A furnace filter in front of a low vent, paired with an exhaust fan high on the opposite wall, works well.
- Relative Humidity (RH) – Never higher than 40%. Unless you're in an actual desert, you need a dehumidifier. With one, you can skip the filtered airflow above, though a fan moving air low and slow (so it doesn't stir up dust) still helps. Heat can lower RH to speed drying, but it's no substitute for a dehumidifier.
- Drying Cabinets – These help keep screens clean after coating and speed up drying, but like heat, they don't replace a dehumidifier.
- UV Light – The screen room needs zero UV light. Use UV filter sleeves on fluorescent fixtures, or source LED lamps that don't output in the 310-420 nanometer range. Turn the lights off when you're not in the room.
- Screen Racks – Worth the investment. Vertical racks for unexposed screens (coated or uncoated), horizontal racks for screens while the emulsion is drying.
2. Choosing a Coating Trough
- Clean – No nicks in the coating edges. Dirt and nicks can mess up your coating.
- Length – At least 4 inches shorter than the I.D. of your screen.
- Edges – A rounded edge and a sharp edge for manual coating. Get a trusted brand.
3. Clean Screens With Good Tension
- Frame – Aluminum only, either static (glued) or retensionable (like roller frames).
- Flat – Check the screen on a flat surface. If it rocks, don't use it. Fix retensionable frames; recycle static ones.
- Tension – Static frames need at least 20 newtons (N/cm²). For retensionable frames, consult a mesh chart and set a standard for your shop based on the mesh count.
- Screen Cleaning – Remove ink, remove the stencil, remove ghost/haze as needed, degrease, and dry the screen as dust-free as possible. A clean wet/dry vac dries screens quickly without depositing dust. If you skip a degreasing step, make sure your ink degradant contains a surfactant to remove greasy residue.
4. Choosing a Reliable Emulsion
Consult your supplier or the emulsion manufacturer, and choose one appropriate for your ink type, reclaim method, and press-side solvents. Color is added purely to make pinholes easier to spot, not for performance.
Emulsion Types Explained
- Diazo – Either solvent-resistant or water-resistant, but not both. A fine choice if your shop only runs one ink type.
- SBQ or Photopolymer – Very fast exposure, but the wavelength of UV LED light sources isn't optimal for this chemistry.
- Dual Cure – Combines diazo and SBQ/photopolymer crosslinking into one emulsion. The most forgiving and robust option, and the better fit if you're coating under UV LED. Trade-off: slower exposure than single-cure emulsions. If you do run SBQ dual cure, dry the screen after developing and post-expose for 3X normal exposure time for best results.
Rise Screen Solutions Emulsions
Rise Screen Solutions is Grimco's exclusive screen printing product line, sold only through Grimco. Beyond emulsions, Rise also covers stencil remover concentrate, spray adhesives, screen frames, and blockout tapes, so it's worth a look for more than just your coating room. Rise offers two emulsion options, both suited to any ink type and available in 1- and 5-gallon sizes:
- Rise SBQ Emulsion – A single-cure SBQ formula for shops that expose under traditional light sources and want fast exposure times.
- Rise Dual Cure Emulsion – A dual-cure formula built for shops running UV LED exposure units or looking for the most forgiving, robust screen.
Not sure which one fits your shop? This video breaks down the difference between SBQ and Dual Cure emulsion so you can match the emulsion to your exposure setup:
5. Proper Coating Technique
- Trough Edge – Use the rounded edge unless your mesh count is very low or very high. Use the sharp edge to uncoat a mistake.
- Coating Manually – Hold the screen in one hand and the trough in the other without stooping; ideally, only your arm moves. Firm, even pressure and consistent speed are the keys, with the trough's angled edges gliding along the screen mesh.
- Passes – Follow the emulsion recommendations. Always coat the squeegee side last. After the last pass, the print side should look really smooth and glossy.
- Drying – Dry the screens print side down.
- Storing – Once coated screens dry store them vertically to keep them clean.
6. Standardizing the Process
Consistency is what separates a shop that makes good screens sometimes from a shop that makes good screens every time. Standardizing your screen printing process means documenting each step — coating, drying, exposure, washout — so any trained person in your screen room gets the same result on Monday morning that they get on Friday afternoon. Here's what that process should include:
- Train everyone, and write it down. Word-of-mouth training drifts. When people understand why each step matters, not just what to do, they catch problems before those problems reach the press. Document your process and keep it current.
- Set an acceptable screen tension range. Aim for a minimum of 20 N/cm and check every screen with a tension meter as it comes out of reclaim. It takes seconds and saves real time in setup and registration. Reserve out-of-spec screens for one-color jobs — or retire them.
- Use one documented coating process. Post it in the coating area where it's visible. If a screen coating machine fits your budget, buy one: it never gets sick, never has an off day, and lays down the same emulsion thickness every pass.
- Check humidity before you expose. Read the hygrometer in your drying cabinet or screen storage area. Above 40% relative humidity, the screen isn't dry enough to expose. Pro tip: coat in the late afternoon and dry overnight — you're far less likely to re-wet screens that have already dried.
- Build an exposure time chart. Use an exposure calculator to find the correct exposure time for every mesh count and emulsion color combination you run. Post the chart. Follow the chart.
- Soak before you wash out. A few minutes in a dip tank of clean water after exposure lets fine detail release without blasting the stencil off the mesh.
- Tape and touch up on a light table. If your process is dialed in, you should have almost no pinholes to fill.
- Diagnose every failure. When a screen fails, find the exact cause and fix it at the source. Skipping this step is how the same problem shows up again next month.
These are the tools every screen printing shop should have on hand. And if you want to dig deeper into emulsions and screen chemistry, learn more about Rise Screen Solutions here.
That's it. Follow these guidelines and you'll be well on your way to making better screens, wasting less time on press, and making more money.