What Are Press Marks and Why Do They Happen?
Press marks, also called pressure marks or halo marks, are visible lines or indentations left on fabric after heat pressing. They appear where the edges of the heat press platen meet the garment, creating a distinct outline that has nothing to do with your printed design. On light-coloured polyester, they can be subtle but still noticeable. On darker or more textured fabrics, they stand out even more.
The cause is straightforward: the edge of the platen applies concentrated pressure in a narrow line across the fabric. The fibres in that line get compressed and slightly flattened compared to the surrounding material, which catches light differently and creates a visible mark. Anything that sits between the platen and the lower pad, like seams, zippers, buttons, or even fabric folds, creates uneven pressure points that make the problem worse.
The good news is that press marks are almost entirely preventable with the right preparation and technique. Here is how to avoid them.
Pre-Press the Garment
Before you even position your sublimation transfer, pre-press the garment for 3 to 5 seconds at your normal sublimation temperature. This step does two important things. First, it drives off any residual moisture in the fabric. Polyester can hold onto moisture from storage or shipping, and that moisture turns to steam during a full-length press, which can cause both press marks and colour issues. Second, pre-pressing flattens the fabric and relaxes the fibres, giving you a smoother, more uniform surface to work with.
Open the press, smooth the garment flat, and close it briefly. When you lift the platen, you should see steam rising from the fabric. That is the moisture leaving. Let the garment cool for a moment, reposition it if needed, then proceed with your transfer.
Use a Silicone Pad Inside the Press
A silicone pressure pad (sometimes called a silicone equalising pad) sits on the lower platen of your heat press, underneath the garment. It is typically 3 to 5mm thick and made from heat-resistant silicone foam. Its purpose is to distribute pressure more evenly across the entire pressing area, eliminating the hard pressure line that the platen edge creates.
Without a silicone pad, you have a rigid metal platen pressing down onto a relatively thin garment, and the pressure is most concentrated at the edges. With a pad, the silicone compresses slightly under load, cushioning the transition between pressed and unpressed areas so there is no sharp line. If you regularly sublimate onto sublimation garments, a silicone pad is one of the most useful accessories you can own.
Position the Garment to Avoid Obstructions
Seams, zippers, buttons, collars, and hems all create raised areas on a garment. When the heat press closes, these raised areas receive more pressure than the surrounding flat fabric, resulting in visible marks and uneven transfers. The solution is to position the garment so that these obstructions are not under the platen.
For t-shirts, this usually means pulling the garment over the lower platen so that only the front panel (or back panel) sits on the pressing surface, with the side seams hanging off the edges. For garments with zippers, position the zip area completely outside the platen footprint. Buttons on polo shirts should be placed off to the side or over the edge of the lower pad.
Take a moment to feel across the pressing area with your hand before closing the press. If you can feel any lumps, ridges, or thickness changes, reposition the garment until the area under the platen is as flat and uniform as possible.
Use Protective Paper Above and Below
Place a sheet of protective paper (also called butcher paper or silicone-coated parchment) both above and below the garment during pressing. The sheet above protects the fabric from direct contact with the upper platen and catches any ink that might bleed beyond the edges of your design. The sheet below protects the lower pad from ink transfer and provides an additional cushioning layer.
Protective paper also helps with press marks specifically because it adds a thin buffer between the platen edge and the fabric surface. This slight extra layer softens the pressure transition at the platen edges. Replace the protective paper regularly, as ink residue can build up and transfer onto future projects.
Do Not Over-Tighten the Press Pressure
More pressure does not mean a better transfer. Sublimation relies primarily on heat and time, not pressure. The press needs to hold the transfer paper in firm contact with the fabric, but cranking the pressure up beyond that point only increases the likelihood of press marks and can actually damage the fabric fibres.
Aim for a medium pressure setting. A good test is the paper pull test: close the press on a sheet of plain paper. You should be able to pull the paper out with moderate resistance. If the paper tears or will not move at all, your pressure is too high. If it slides out with no resistance, it is too low.
Dealing with All-Over Prints
All-over prints, where the design covers the entire garment panel, present extra challenges because the transfer paper extends to the very edges of the platen. If your platen is not large enough to cover the full garment panel in one press, you will need to reposition and press again, which risks creating a visible overlap line.
For all-over work, use the largest press you have available. If you must do multiple presses, overlap the second press slightly onto the already-pressed area, using lower pressure for the overlap zone to minimise the visible line. Some printers use a swing-away press rather than a clamshell style for all-over prints, as the vertical closing action of a swing-away distributes pressure more evenly than the angled closure of a clamshell.
Press marks can be frustrating, but once you build these steps into your routine, they stop being an issue. Pre-press, use a silicone pad, position garments carefully, protect with paper, and keep your pressure moderate. These five habits will give you clean, mark-free results on every garment you press.