Screen Printing Coroplast Signs
All businesses have three imperative questions to answer:
- How to grow.
- How to increase profits and reduce overhead.
- How to increase the competitive advantage.
Could screen printing Coroplast signs be the answer?
Already have screen printing equipment? Printing Coroplast signs is possibly the easiest way to offer a new product to your clients.
At first, venturing into signs can seem daunting but is really very easy with the equipment you already have. If you already own a screen printing press then you will need to add a platen large enough to hold the standard 18×24 coroplast sign. This would mean getting a 20×26 platen. The most effective way to print signage on a manual press would be with a vacuum platen. The suction from the pallet holds the sign flat and in place for registration. You can use a wooden platen, as well. Just spray a little spray tack on the board to hold the sign in place. You will only need one of these platens. This is due to the nature of graphic inks which only allow you to print one color at a time. Graphic inks are ‘air dry inks’ and need time to dry between colors. We will discuss that later in the article.
Now that you have the platen you will need a screen. Again, we need to get one large enough to hold a design to go on an 18×20 sign blank. An Aluminum 23×31 screen will suffice for this application. You will want to use a 200 to 230 mesh screen when using solvent ‘graphic’ inks. This type of ink is fairly thin and needs a tighter mesh to print effectively so as not to run through the screen.
With the new screen you will need the correct scoop coater, squeegee, and emulsion. It is recommended to use a graphic emulsion when using solvent based inks. The dual cure DCM by Chemical consultants is a good one to start with. Emulsion choice is very important here. Graphic emulsions are solvent resistant, allowing you to use harsher chemicals required to clean the inks used in sign making. If you use a non-solvent resistant emulsion, such as DXP or SWR you run the risk of a chemical reaction between the solvents used and the emulsion. This will cause the emulsion to “lock” into the screen rendering it un-reclaimable. You want a scoop coater and squeegee large enough to cover the entire image area in one motion. This usually means 19” for both.
With the correct emulsion you coat the same way you would for doing other screen printing projects. Apply pressure and pull the scoop coater upwards starting with the print side and then turning to the squeegee side. Let the screen dry with print side down. Now you are ready to expose. Exposure times vary depending on your exposure unit, emulsion type, and thickness of emulsion layer. It is recommended to do a step wedge test to determine the proper exposure time for your conditions.
Now that you are exposed it is time to print. You will want to use the appropriate ink for doing signage. There are several graphic ink lines; each has a set of products it adheres best to. For coroplast signage it is suggested you use corrugated plastic ink. As mentioned earlier this is an air dry ink. It will dry in room temperature in as little as 30 minutes. You can speed up the drying process by putting a fan on the printed signs. One feature of air dry inks is that you can only print one color at a time. This means that if you have a multiple color design you will print out the entire first color, set to dry, register and print the second color, set to dry, and so on. It can be laborious if you have a lot of colors. It is very similar to the way signs are done with vinyl but much faster.
Make sure that you mix the ink thoroughly prior to adding it to your screen. This will ensure that the pigment is distributed throughout the entire container. If you feel the need to thin the ink, take the amount you plan on using and place it in a new container and thin the new container rather than the original can. It doesn’t take much thinner to over think an ink and make it unusable. It’s better safe than sorry and only thin what you will need at the time.
Solvent inks print very similar to printing with water base inks. As an air dry ink they can start to evaporate in your screen. You will want to make sure you flood the image area between prints to reduce losing detail as you go through the run. You can also add reducer to extend the life of the ink during the printing process. To print effectively, make sure you flood between prints and move at a steady pace.
When you are done printing you can card the ink back into the container and wipe out the screen and clean the squeegee using a solvent cleaner. The most common are RC-5 (slow evaporating) and lacquer thinner (fast evaporating). Always make sure to clean right away and not leave the screen for any extended period of time. If you need to stop in the middle of a run, make sure you clean the image area before leaving it. Graphic inks will seal up the mesh if left to dry in a screen and ruin the screen or squeegee they are left on. Once clean you can either store the screen for future use or reclaim for a new design.
The reclaim process is the same of graphic emulsion as it is for DXP or SWR. You will want use an emulsion remover such as ER80, a pressure washer, and degreaser such as Neutralize from Chemical Consultants.
The ink is drying too quickly in the screen.
You can combat this by adding thinner to the ink. Also, be aware of the temperature in the room when printing. If it is too warm in the area the ink will dry faster. Try printing earlier in the day when it is cooler.
Strings of ink stretch between the screen and sign blank when lifting the screen.
This can be an indication of either ink that is too thin or static electricity in the air. You will want to thicken the ink if it is too thin. For static electricity, you can use a dryer sheet to wipe the surface of the blank or add humidity to the room. This can be done by wetting down the print area or using a humidifier while printing.
Ink was left and dried in the screen/ on the squeegee.
You can try to save the screen or squeegee by wetting down a rag with either RC-5 or Lacquer thinner and lay it on the ink area for several minutes to soften up the ink. You have a better chance of this working if the ink has been dry for less than 24 hours.
In conclusion: Your clients are relying on you to fulfill their apparel needs right? So many ‘apparel jobs’ are connected to events (sporting, family reunions, etc.) So ASK! Ask if signage would help them to promote their event. Otherwise, you run the risk of surrendering profitable sign printing business to your competition.