#1 on the list for good reason! If you don’t have one, chances are you have had issues like unpredictable under or over exposed screens, films sticking to your emulsion, inconsistent exposure times, and/or difficulty reclaiming. Emulsion must be properly dried, meaning the moisture has evaporated from the interior of the emulsion coating. Many printers struggle with what we call “the jelly doughnut” effect, meaning the emulsion appears dry on the surface but has a gel-like interior lurking beneath. This very thin interior layer of moisture will wreak havoc on your exposure and development of quality stencils. When properly dried, emulsion “cross-links” or sticks to the mesh resulting in easy exposure and reclaiming.
Adding a dehumidifier to your screen room allows you to control the amount of moisture in the air which increases the speed and consistency of your emulsion properly drying once applied. Ideal screen room humidity should be around 30%, never above 40%. Your dehumidifier doesn’t need to be fancy, but ideally it should have a feature to set your preferred humidity level. Once that level is reached, it will stop running until the air becomes too humid again. Many models require you to empty the water tank once it is full to keep operating, while others offer continuous operation thanks to a hose bib attachment for constant draining (ideal if you have a floor drain). They can be purchased at any general retailer starting at around $35.00 for a super basic, smaller model. This screen room superstar won’t set you back much, and will pay for itself in time saved long term.
2. Space Heater
Combined with a dehumidifier, a space heater will pack the one-two punch needed to achieve perfectly dry screens every time you’re ready to hit the exposure unit. Colder temperatures (below 70ºF) make it difficult for moisture to evaporate properly from emulsion, while overly hot temperatures (above 105ºF) will cure the emulsion entirely and your screens won’t expose. Ideally, your screen room temperature should hover around a toasty 90º F for optimal drying conditions.
Basic space heaters can be purchased at any general retailer starting at around $25.00. Make sure to choose a model that allows you to set a max temperature to kick off the heater once it senses the room is warm enough. Similar to dehumidifiers, the size you should buy will largely depend on the size of your screen room and general climate based on your region. Other safety features to consider are protected heating elements and tip-sensing auto-shutoff.
3. Digital Thermometer/Hygrometer
Just because you’ve set your dehumidifier and heater to the desired levels doesn’t mean your space will maintain that 100% of the time. This little multi-purpose gauge will give you excellent monitoring capability to be sure your dehumidifier and space heater are getting your screen room to the 30% / 90ºF combo we’ve mentioned, or how to adjust accordingly. The thermometer will read the temperature while the hygrometer will read humidity. If your screen room is above or below the ideals, adjust your settings and wait a few hours before attempting to coat screens. These are widely available at general retailers, and well worth a $10-$20 investment.
4. UV Resistant Lighting
If your screen room is at the appropriate humidity and temperature levels and you’re still having issues with exposure, development, or reclaiming, the culprit may be your screen room lighting. Screen emulsion is UV-sensitive, meaning it hardens when exposed to any UV light waves. This includes overhead tube lighting, LED lights, and yellow bug-detracting lights. WE REPEAT… DO NOT USE YELLOW BUG-LIGHTS IN YOUR SCREEN ROOM. These lights simply eliminate the long-wave light spectrum humans see best and emit the short-wave spectrum of light closest to UV light waves (which bugs cannot see). Therefore, when you use a bug-light in your dark room, you are essentially blasting your screens with the very UV light you want to avoid until your screen is dry and ready for the exposure unit.
The best option is to cover your bulbs in UV filtering safety sleeves. These are thin yellow sleeves that cover your bulbs to block the UV light they emit, while giving you optimal visibility in the dark room. Tech Support offers top-quality safety sleeves of varying sizes starting at $12.00 each. If you do not have tube lights and need a screw in bulb, look for red-bulb lighting similar to what you’ve likely seen in photography dark rooms. They won’t provide the same visibility as a yellow safety-sleeve cover will, but it will avoid the issue of blasting your screen with UV light. You can snag a two-pack for around $15.00 from general retailers or hardware stores.
5. Power Washer / Garden Hose Nozzle / Two-Way Hose Splitter
Last but certainly not least, every efficient screen room should have both a power washer and a standard garden hose nozzle connected by a two-way hose splitter leading to the wash out booth. Why all three? The intensity of a power washer is essential to a few steps of reclaiming, specifically in removing emulsion and ghost/haze images remaining in the screen. If you try to do these with a basic garden hose nozzle, your screens will never get fully clean enough to recoat without issues. The only power washer specification we’d recommend looking for is a model that is at least 1500 PSI. A basic power washer will get the job done, but is essentially disposable in nature and will need replaced relatively frequently. We went through four or five before settling on the reliable Rhinotech 1500CP for our in-house screen room.
All other aspects of the development and reclaim processes benefit from a less-intense basic garden hose nozzle. For example, you don’t need a power washer to rinse stencils out after exposing, or for removing ink or cleaning squeegees. The consistent and even pressure supplied by a garden hose nozzle will provide an easily controlled and less messy option for most wash out booth activities.
Nothing fancy is necessary. For about $4.00 you can get a classic nozzle with a single adjustment point that provides a range from jet-spray to gentle cone. For just a few dollars more, there are nozzles that provide multiple spray patterns. Our favorite settings include the shower spray, horizontal and vertical fan, or the cone.
You’ll also benefit by adding two-way hose splitter to your wash out booth set up. This will allow you to keep both your power washer and garden hose nozzle ready for use at a moment’s notice instead of swapping what is connected to your water source every time you get to work. Prices for hose splitters average around $10.00 each.
No matter your level of experience as a printer, setting up your screen room with these five essential items will dramatically improve the speed and consistency of your development and reclaim processes. We’d love to see pictures of your screen room set up, or please comment below with screen room tools you couldn’t live without!