Before pressing, it is important to look up the brand and type of HTV that you are using, so you can find the best temperature to set your heating tool to. HTV can need temperatures anywhere between 270 - 320 degrees Fahrenheit (135-160 degrees Celsius), so it really helps to know what temperature that specific HTV needs to adhere best. When looking up the temperature, companies usually also recommend how long to press it for. This is also helpful information to have.
To press your HTV design onto your shirt, position your design, lay your pressing cloth over the HTV and clear plastic sheet, and allow your iron to heat up to the desired temperature. Once it is fully heated, set your press over the design and let it sit for the recommended time (usually anywhere between 10-20 seconds). Then pick up the press and allow the HTV to cool slightly. If your iron or press is not big enough to cover the whole design, simply repeat to move the press around, so you can press each area of the HTV.
HTV usually needs to be pressed 2-5 times to adhere to the T-shirt. Allow the HTV to cool slightly, and lift one corner of the plastic sheet to see if the vinyl is separating from it. If not, repeat to press the design for a few seconds, allow it to cool, and check if it’s separating again. Repeat these steps until the vinyl is stays on the shirt and does not come up with the plastic layer.
If your clear plastic layer begins to warp, shrink or discolor, stop ironing as your HTV is probably adhered to the shirt, but is just stubbornly also stuck to the plastic sheet. In this case use a small tool to hold the vinyl against the shirt as you pull up a corner of the plastic sheet to see if you can get them to separate (It should not be hard to separate. If it is hard, the HTV needs more pressing time, and you are probably pressing for too long at a time which is causing the plastic sheet to warp). If this works, you can move to the next step. If it doesn’t, keep pressing and cooling, but in shorter bursts.