There are two terms that are commonly mentioned when it comes to t-shirt screen printing inks: “Water-based” ink and “Plastisol” ink. Which one is better for your design?
That really depends on a lot of factors. Both are great choices and have unique qualities.
Water-based is pretty much as it sounds, it’s made with water. Plastisol is derived from plastics. Below we will take a look at some of the advantages and disadvantages of each ink to help you decide which is the best for you: 

Water Based Inks
Waterbase is a two part system that requires base and pigments. Pigments are added to base to create colors. Waterbase lends itself very well to white and light fabrics.

Waterbase ink is a great alternative to plastisol ink. With waterbase you are able to achieve a vintage – soft hand. Ink seeps into the fabric and creates minimal hand. Since waterbase inks are free of plastics and PVC, it is also eco-friendly.

When printed on dark colors the results are muted and Pantone colors are difficult to achieve. Waterbase can only go thru open mesh counts. Halftones and gradients are difficult to achieve.

 Plastisol Inks
Plastisol comes in two forms, its comes as RFU (ready for use) and as a system to mix, mixing base + pigments. The beauty with plastisol is the color consistency and accuracy. Pantones are set in a system and formulas create PMC colors. Plastisol contains resins and plasticizers and require a temp minimum of 350 degrees to cure. If this temperature is not met, the ink will under cure and crock/wash away. 
Plastisol is the most common ink used in t-shirt printing. Unlike waterbase, this ink will not dry out and stay fluid in the screen. Plastisol can be used through all ranges of screen mesh counts. Works very well on lights and darks and key to using in designs that have halftones and gradients. Plastisol ink has a wide variety of specialty products and waterbase has a limited amount of specialty applications.
Plastisol is composed of resins and PVC. The hand feel is felt on the garment. Waterbase has virtually no hand. Because of the nature of the ink it is not suitable for vintage feel or hand. There are techniques that are used to lower the viscosity to make it reduced, this will help with hand but will not appear as soft as waterbase.

water VS plastisol