Ink type can make a huge difference in how your project looks and feels. With the design in mind, how do you picture it? Do you want something subtle and soft like water based or discharge? Do you want something bright and vibrant like plastisol?
Something to keep in mind is what your audience will appreciate. If they're a sports fan, consider plastisol as it feels and looks like what you commonly see on sports jerseys. That kind of buyer may associate thickness, and being able to feel the ink with quality.
If your audience is more fashion or comfort-minded, look at water based and discharge which are super soft and comfortable. Those inks also lend themselves well to designs where you want a vintage look and customers that prefer less hand feel in the print. Water based and discharge printing can often not be felt at all after the garment is washed for the first time.
Learn about the most commonly used ink for the creation of custom shirts; Plastisol.
The perfect ink for the softest prints when combined with poly-blend fabrics.
Discharge ink is a special ink that can offer you bright prints while maintaining the ultimate softness of your shirts.
If you're still undecided, something that can help you choose is starting with your shirt fabric. If you have your shirt type in mind, you've already narrowed down your choices. Here's an ink decision tree to show you what type of ink works best on each shirt type.