There are two main types of inks that are used for screen printing, each with their own advantages and disadvantages.
Water-based inks utilize either dyes or pigments in a suspension with water as the solvent. The evaporation of the water is necessary to set or cure the ink.
Plastisol is a thermoplastic ink. It is composed of PVC (polyvinyl chloride) particles suspended in a plasticizer. High temperatures are required to cause the molecules of PVC resin and plasticizer to cross-link and fully cure.
Advantages of Water-based Inks
Water-based inks tend to be a little more environmentally friendly and give printed fabrics a soft “hand”. A soft hand means that your hand cannot easily feel the ink when it passes across the surface of the fabric. Water based inks printed on fabric can also be ironed (Plastisol will melt and smear if heated up to it’s curing temperature). For paper screen printing applications water-based inks are ideal as they will air dry as the water content in the ink evaporates. Clean up is easy and can be done without much impact to the environment.
Disadvantages of Water-based Inks
Water-based ink is much more difficult to cure than plastisol for fabric applications. With water-based ink, the curing temperature must be reached and then held until all of the solvent (water) is removed. If you don’t fully cure the ink (for example on a T-shirt), the ink will fade with repeated washings. If water-based ink is left in open mesh for even a short period of time, it can clog the mesh and ruin the screen. You don’t really have to worry with regards to paper applications however. The other thing is that water-based inks will break down regular emulsion very quickly and even break down water resistant emulsions over time leading to screen breakdown for longer print runs.
Advantages of Plastisol
Plastisol inks are not water-soluble and the ink will not dry if left in the screen for extended periods of time. It can be left in the screen for extended periods of time without worrying about clogging the mesh. Platisol will not break down the screen emulsion like water-based inks. They also happen to be very opaque and great for applications on colored fabric.
Disadvantages of Plastisol
Plastisol inks will not air dry and need to be cured (heated) as a result. Curing the inks can be done with a flash dryer, or more inexpensively, any home oven. Be careful not to burn your house down! Most plastisols need to reach a temperature of about 350 Fahrenheit before being fully cured.
Plastisol tends to sit on top of the threads instead of soaking into them, which typically results in a raised, plasticized texture. There are, however, plastisol additives that can give the ink a softer “hand”. If the ink is under-cured, the print will crack and peel over time.
Plastisol inks are generally considered harsher on the environment. Fortunately, there are a number of plastisol inks on the market that contain less toxins, and there are also eco-friendly solvents that are available for clean up.