Pre-Press and Humidity: Friend or Foe?

Humidity plays different roles in the pre-press department and its processes. For example, do not keep your inkjet printer in the same room you coat, dry and expose your screens and especially nowhere near your washout station. These processes and screen printing supplies demand opposite conditions.

Inkjet inks air dry, the print head is open to the air much of the time in use. Epson and other manufacturers list in their tech specs the ideal range for humidity. It’s important to operate your inkjet printers in an environment that has a controlled atmosphere. Example humidity range: Operating: 20 – 80% Storage: 5 – 85% (no condensation). Keep your print out of direct sunlight and away from wind from AC vents, fans, windows…a controlled environment delivers the best experience and reduces clogging.

Have a small desktop printer and find it challenging to control the environment? Create a micro environment when the printer is not in use. Cover the printer and place a glass of water under the cover to increase the humidity.

The opposite is true for just about every other portion of the prepress screen printing processes where humidity is your enemy.

Screen Coating and Exposure:

To a screen printer coating and drying screens humidity is no friend. Humidity will cause a number of screen-making issues.

While it is true that using a two-part emulsion requires the addition of water to the sensitizer, it is most important to fully remove that water during the screen drying process. High humidity in your screen making room is a recipe for disaster which is why all screen printers should spend some time ensuring their screen making environment meets standards. Having a proper heated, vented and filtered screen printing drying cabinet is your first and best step to repeatable, reliable success.

A Hygrometer is an important tool to have on hand; inexpensive and valuable, get one right away. What you will likely find is that your environment is way moister than you need it to be. Then you can start working on improvements.

Let’s talk about dehumidifiers, by the name alone you’d think as long as I have one of those I’m ok, right? Wrong. In fact, most dehumidifiers work so poorly they actually add more water back into the atmosphere doing the exact opposite of what they were purchased for. Allow me to explain. There are dehumidifiers that work well and others that do not, generally the less expensive models you buy from the local appliance store are terrible.

Built poorly, they use small fan motors that run very hot, that hot air passes over the coils, the coil sweat then condenses into the drip pan. That pan sits in your room for hours if not days and evaporates the water back into the atmosphere. It’s a death loop of humidity. Each time you empty that pan do you really think all that water came for the air? No way, that is water that was actually manufactured by the very device you purchased to remove water.

A proper professional dehumidifier has a pump to remove all water from the system and push it out of the building. Look at brands such as Oasis or Global, such as these professional disaster recovery dehumidifiers.

Built with larger more capable fan motors and internal pumps (not pans) that remove the water from the room immediately. These devices run cool and efficient. They are also capable of removing gallons of water per day which is generally only needed after a flood. Therefore, if your goal is drier air this is the proper unit for that.

Now that you have a proper dry environment your screen making will go so much better, be more predictable and you’ll produce superior screens that expose better, hold greater detail and last on press longer. Couple this with a proper screen drying cabinet and you have a well-developed screen making environment. After all we are screen printers, the screen is the most important part of the process and our careers. Treat your screens poorly and you’re treating your business poorly.

Are there ramifications to screens that are not fully dried (cured)? Yes, just as we are concerned with curing our inks on the shirt we also must be concerned with curing the emulsion on the screens. Not having a proper drying cabinet means your screens are subject to the atmosphere they are being dried in. Blowing air across an emulsioned screen in a homemade rack in a room that has too much humidity is counterproductive. Your screen will always have a degree of moisture to them when exposed. You want your screen emulsion to be bone dry. Any moisture in the emulsion will not only cause exposing and wash out issues, but it will also destroy your films.

Do I have your attention now? Yes, any moisture left in your emulsion will certainly reactivate the ink on the film when pressure and light/heat is added during the exposure process. When you pull your films off the screen more than likely the ink is tearing away as well. If you are altering your exposure process in any way to reduce this issue you are likely also hurting the process in another way.

Film Printing:

Screen printers use dye ink to print their best films, dye ink such as Freehand’s premium quality black Dmax™ dye ink for inkjet printers contains water. It’s the best ink for our needs, yet we also need to handle it properly to achieve the best results.

Just like our press inks and screen emulsion our film must be “cured” as well. Properly engineered dye ink will dry nearly on contact with a compatible emulsion coated polyester film. In cases that the ink needs a bit more time to air dry the water will evaporate leaving behind a residue of dye that fuses to the film coating. Giving your films enough time to “cure” will increase durability during the screen making process. Make note that even if a film is cured but your screen emulsion is damp that will reactivate the dye causing instability. Once again, water goes from being a friend to foe when improperly managed.

Screen Printing Supplies and Humidity Conclusion:

Take the time to fully understand the systems of your industry, the needs of your screen printing products and handle them properly to achieve repeatable success. By investing in the proper equipment rather than cutting corners you’ll not only be more profitable, but screen printing will be an enjoyable medium of expression.

Freehand and you, together we got this.