Are your t-shirts cotton?
Most of the basic t-shirts offered for sale by the artists on the Printerval marketplace are cotton. There are a few exceptions to this (like the tri-blend tees), but that can be clarified in the ‘Style Information’ tab when you toggle between styles.
It’s also important to note that all of the full-bleed garments (graphic t-shirt, sleeveless top, etc.) are constructed from a polyester blend, which allows for the embedded and flowy sublimation prints.