Plastisol vs. Water-based Ink for Textile Printing
There are two main types of ink that are used for textile printing. Water-based ink utilizes 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. This curing can take place either at room temperature or using a forced-air dryer depending upon the specific water-based ink used and the speed or volume of production.
Plastisol ink is a PVC (Some inks are Phalide Free) based system that essentially contains no solvent at all. Along with UV ink used in graphic screen printing, it is referred to as a 100% solid ink system. Plastisol is a thermoplastic ink in that it is necessary to heat the printed ink film to a temperature high enough to cause the molecules of PVC resin and
plasticizer to cross-link and thereby solidify, or cure. The temperature at which most plastisol for textile printing cures at is in the range of 300 °F to 330°F
Both types of ink are very popular. However, for the most part, they are used in very different applications. Plastisol is the ink of choice for printing of finished goods such as T-shirts, sweatshirts, jackets, and tote bags. Water-based ink is the ink of choice for the printing of yard goods; either in piece form or on the roll. Both inks have technical advantages and disadvantages for use in specific applications. They also each have their own environmental impacts and these should be considered for the particular application and shop setup.
Advantages of Plastisol
What this statement means, is that it is very beneficial, and cost effective, to keep plastisol colors from being contaminated by dirt, lint, or even other colors of ink. By maintaining clean shop practices, there will be a great reduction in ink waste. Clean ink can be returned to the original ink container for reuse. There is no degradation in the quality of plastisol as long as it is not mixed with other colors or contaminated with foreign materials.
Plastisol that has been contaminated with other colors is can still be retained in a separate container for blending with other waste ink. Often times this waste ink can be used to create new colors or, it can be over pigmented with fresh pigment to create a dark color, such as black, for use on less critical jobs.
With good plastisol ink management, waste can be reduced to a very small percentage. Plastisol product that is unusable is not considered hazardous waste in most municipalities as long as it is solidified (cured). The best way to achieve this cure is to heat the waste container itself to 160 °C (320 °F) for a period long enough to cure the ink all the way through. In practice, a one gallon container of plastisol will cure all the way through in approximately one hour.
If the plastisol needs to be disposed of in an uncured state, then hazardous chemical regulations usually apply. For either cured or uncured disposal, it is recommended that you always check with local regulatory agencies.
The biggest environmental hazard in the use of plastisol comes in the screen and equipment cleaning steps. In order to emulsify the ink for easy removal from screens, squeegees, flood bars, spatulas, and work surfaces, it is necessary to use some type of solvent. The waste ink and the solvent must be disposed of properly in order to minimize environmental impact.
The screen printing industry has been very proactive in the creation of products that can minimize the impact of these cleaning processes. Environmentally-friendly solvents, and solvents that are more environmentally sensitive than traditional petroleum-based solvents are readily availble. In addition, there are many types of filtration and cleaning systems available to capture inks and solvent residues to minimize the solids that are discharged into the sewer system.
Water-based Ink Systems
Water-based inks are defined as those that utilize water as the main solvent. That does not mean, however that water is the only solvent. It is significant to note that many water base inks contain co-solvents which may even be petroleum based solvents. The reason these co-solvents are used varies, but one of the key reasons is to decrease the time and heat necessary to cure the ink film on the fabric.
Advantages of Water-based Inks
Disadvantages of Water-based Ink
Water-based Ink Cleanup
There is a common misconception that because water can be used for cleaning screens, squeegees and tools, that the waste water can just be discharged in the sewer. However, the water-based ink is not just water. There are pigments, binders, thickeners, and sometimes, even co-solvents in the ink residue.
Screen cleaning systems that can at least capture the solids are still recommended. In addition, water-based that has not been catalyzed can be returned to its container for reuse. If the ink has been catalyzed, it should be considered hazardous waste unless it can be dried out (all water and solvent removed) before discarding. If it cannot be dried, it should be disposed of as hazardous waste.
Whether printing with plastisol or a water-based ink system, you are still printing a chemical compound. Therefore, it is essential that proper handling and disposal methods be practiced. As stated above, there are advantages and disadvantages to each ink system. The key is to use the proper ink for the application, minimizing waste product, and always dispose of waste properly.
Usage Recommendations Plastisol Water-base
T-Shirts/light colors Excellent Excellent
T-Shirts/dark colored Good Poor
Nylon Jackets Good Poor
Towels Poor Excellent
Yard goods Poor Excellent
Sporting Goods Excellent Poor