Not all polyester fabric and garments are created equally. Just because the tag says it is 100 percent polyester does not mean that a garment is going to sublimate well. Some garments might have too low of a thread count, surface treatments that will affect the transfer or low white points. You should test all garments before committing to use that type of performance fabric with a customer. You should also be wary of accepting customer-supplied garments without being able to test them first.
—2 Regular Guys, MontCo Consulting