You won’t always need to wash clothing before you prepare it for heat transfer vinyl, however, it is recommended that you pre-shrink the fabric as much as possible.  This means your t-shirts and other garments will be ready for an even pressing with craft vinyl/t-shirt vinyl for the best results.  100% cotton products, particularly, respond well to pre-shrinking.

However, make sure that you DO NOT use fabric softeners on garments before you use heat transfer vinyl.  Heat press vinyl may not be effective on clothing or material that has been exposed to such detergents. This means a straightforward wash – perhaps even just with warm water in a basin or in a washing machine – will be enough in terms of preparation required.