There are several solutions you can use, including transfers with a low-temp application, dye-blocking transfers, cover sheets, and equipment with a heated lower platen.
Ever since athleisure became a trend, heat transfer manufacturers have come up with materials and adhesive systems that apply at a lower temperature. Just slightly more than 10 years ago, most transfers applied between 320-380 degrees F. If you’ve ever used transfers on heat-sensitive fabric at that temperature, you know the discoloring that can occur and the marks it can leave on your items.
Today, you can find transfers that apply as low as 235 degrees F. Most heat-sensitive fabrics start to show marks at about 280 degrees F. Talk with your manufacturer about the items you plan to press. Odds are, they will have a recommended material for the job.
In addition to the problem of heat press marks, performance fabrics also provide significant risk for dye migration. Dye migration happens when the press heats the item to the activation temperature of the dye in the garment. This activation causes the dye to migrate through the transfer and discolor it. Sometimes this discoloration happens immediately, and sometimes it takes weeks to migrate completely. Heat transfer manufacturers have helped to alleviate this issue with transfers and vinyl specifically designed to block dye migration. Look for transfers with charcoal backing or made from a silicone base. These not only apply at a lower temperature, but they have a layer built into the transfer to block dye migration.
A cover sheet works in tandem with a change in the application time and temperature of your transfers. The idea is that the cover sheet defers some of the pressure and heat from the garment. The cover sheet style that has the most success in minimizing heat press marks is gray silicone. It’s the same material that makes up the lower pad on your press.
A word of caution with trying this solution: You’ll need to increase your application time to make sure enough heat reaches the heat activated adhesive on the bottom of your transfer.
Lower heat platen
All the solutions we’ve covered so far have made a big difference in how decorators successfully press performance wear. Another solution for the list is heating the garment from the inside out.
This solution works exceptionally well with both low-heat transfers and dye-blocking transfers and eliminates the need for a thick cover sheet during your heat transfer applications.
To make this happen, you have to install a lower heat platen on your press. Typically, this lower heat platen requires a separate electrical plug but will fit on a heat press with interchangeable lower platens. Also, make sure the heat press is threadable. Threadability is very important because you are essentially putting the heat press marks on the inside of the shirt.