Decoration Direction: Tips for Tackling Water-Based Inks

As the entire industry adopts more 'green' practices, here's some advice on how to approach running a water-based ink job for the first time.
June 11, 2008

As a promotional consultant selling eco-friendly products, you’ve probably had customers asking about eco-friendly processes so that they can tout an all-green product. One screen-printing option is water-based inks; however, the proper use of these inks is not without its challenges.

If you’re a screen printer, this article provides handy tips for producing good results from water-based inks. If you’re not a printer, you’ll learn the ins and outs of water-based inks so that when you request an eco-friendly process from your contract printer, you’ll have a thorough understanding of what’s involved. — Ed.

Screen Making Considerations. To print water-based inks, you may have to change emulsions from what you normally use for plastisol printing. Manufacturers of water-based inks make special emulsions for use with these inks and also sometimes a hardener that is meant to help prevent the emulsion from breaking down.

Materials. There are a few simple, but different, tools you need close by as you print with water-based inks. These are a few items that often get overlooked when a plastisol printer prints a water-based job for the first time. Have clean five-gallon buckets of water, with sponges, close at hand at all times. Keep rags or paper towels handy to clean the bottom of the screens when necessary or to dry the bottoms of screens after cleaning them with the sponge. Also, if you are not using waterproof blockout and tape, these items are a "must" to include in your metamorphosis.

Screen Mesh Decisions. Plastisol printers who have long used meshes as fine as 305 monofilament polyester will find they are limited to meshes of 195 and lower when printing water-based inks. Because of the size of the binder particles in water-based inks, meshes finer than 195 will act as a filter and prevent binder particles from passing through the screen to the garment. Also remember, the finer the mesh, the faster the ink can dry in the mesh and cause clogging.

Shop Conditions. Good air flow is required to cure water-based inks, but that same air-flow is an enemy when it comes to the printing process. Fans in the shop are a great help when water-based ink prints are drying and curing, but they will accelerate ink drying in the screens during printing. Fans should be turned off during printing or kept well away from the press.

Printing Considerations. It's necessary to have air flow in your drying chamber to effectively cure the water-based prints, as the ink cures when all the water has evaporated from it. This generally occurs when water-based ink is subjected to oven times and temperatures of 320 F at 90-second dwell times.

Catalysts are available for water-based inks that will allow prints to dry sufficiently enough to stack after they exit the dryer. These prints will continue to cure for approximately 48 hours. The tradeoff for using a catalyst to facilitate drying is you will shorten the shelf life of the ink to approximately four to 12 hours. Without a catalyst, water-based inks have a normal shelf life of up to one year when stored in cool, dry conditions with the ink container closed tightly to stop evaporation.

Flashing. If you're accustomed to flashing once or twice for a plastisol design, your current flash-cure unit may not work for water-based inks. Most flash-cure units designed for plastisol printing may take from 10 to 20 seconds to surface cure a water-based ink. This does nothing more than heat up the platen to the point that it starts to dry ink in the screen.

In terms of presses, most shops can use their current press to print with water-based inks. Manual printers need to remember to flood coat the screen after each print stroke in order to keep the mesh wet, which helps prevents ink drying and clogs. Automatic printers likewise will need to set their machines to do a print/flood stroke where the flood stroke is last.

Cleaning Up Your Screens. Screens made with emulsions for water-based inks clean up easily with water. No solvents are needed, but that doesn't mean the runoff can be sent down the drain. Consult your ink manufacturer and/or municipal officials about proper disposal of waste from water-based inks.

Curing. It's necessary to have air flow in your drying chamber to effectively cure water-based ink. Water-based inks cure in two stages — removing the water from the ink and then cross-linking the resins with the same heat needed for plastisol.

As a water-based print goes through the dryer, it will heat up to a point where the water will start to evaporate, and actually cool the ink surface. The ink hovers at about 180 F, where it will stay until all the water is evaporated from the print. Once all the water has evaporated from the ink, you are free to heat the print up to 300 F and 320 F, at which point it cross-links and bonds with the shirt, just like plastisol.

Source: “Tackling Water-Based Inks for the First Time” by Jeff Proctor, Impressions, October 2007

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