When pressing sublimation blanks, one of the most common issues is blurry results. Blurriness can manifest itself in two different ways: in the form of a duplicate image also called "ghosting" which looks a lot like seeing double or an image that has reduced detail.
"Ghosting" or often seen as the image has shifted Standard blurriness with dull color
During the pressing process, an image may shift position on the substrate causing the sublimation ink to continue imprinting but in a different spot. This most often occurs when the heat press machine is opened and the top platen picks up or accidentally moves the printed image on the sublimation paper while the sublimation process is still going on. This is avoided easily by taping down the design securely onto your substrate with heat transfer tape so that it doesn't shift at any point. For some items like polyester apparel, a spray adhesive may be a better solution as tape doesn't stick to it easily.
Remember that as long as the substrate is still hot, the sublimation ink from the paper will continue to activate. If you pre-press your sublimation blanks, ensure that they are cool to the touch before lining up your printed transfer for pressing.
Blurry, dull image
The second reason why your image might be coming out blurry, especially if there is a loss of detail and a change in color (looking yellow or dull), is over-pressing. Over-pressing can be caused either due to too much heat or too much time. A blurry, dull image is the most common sign of pressing your sublimation blanks for too long or with too much heat. Simply decreasing the time usually resolves the problem.