Heat transfer printing uses high temperatures to print designs on promotional products made of fabric, like apparel, camping chairs, and bags.
If you’ve ever been a Girl Scout and/or a member of a biker gang, you’re familiar with iron-on patches. You know, the ones you press with an iron so the heat melts the adhesive on the back of the patch, making it stick to the fabric.
Heat transfer works a bit like that. Those types of patches are typically embroidered, whereas promotional products usually use various types of paper, film, or vinyl — but the principle is the same. You take whatever it is you want to customize, slap your design on, get it a) hot and b) heavy with a heat press, and if you’ve done it right, it’s stuck to the garment forever.
In case that’s not enough detail for you, here’s some more.
Meet the Heat Transfer Process
Oh, I didn’t think anyone would actually keep reading. Now I’m glad I finished this article and didn’t just copy and paste a chocolate chip cookie recipe or something.
The three main components of getting a heat transfer right are heat, pressure, and time. And as you’ll see, there are some other steps too. We’re so nerdy about this that we even made a video explaining it:
Here’s the step-by-step:
Step One: Print Design on Special Heat Transfer Paper
We say print, and we say paper, but it depends on which of the various types of heat transfer the print shop is using. It could be vinyl, which is cut out into the design, or special ink printed on also-special paper, or film. The point is to take a 2D design and put it on a 3D sheet suitable for heat transfer.
Step Two: Get the Press Hot to Go
The press needs to be hot enough for the particular type of transfer to, well, transfer. This depends on factors like the type of transfer, the fabric the design is being pressed into, and how many colors are in your design.
For example, if you’re printing with plastisol (a type of liquid plastic ink), designs in multiple colors require a higher heat than single color designs. You can see the different temperatures (and pressures, and times) for four of the most popular types of heat transfer at the end of this article.
You also have to keep in mind the fabric you’re printing on, since not all fabrics do well at high heats. As anyone who has ever melted a polyester shirt with an iron can confirm, polyester works better on a lower heat setting than natural fibers like cotton or blends with a high cotton content.
Step Three: Prepare Your Garment for Printing
With a pep talk! No, with its own pre-press pressing. The fabric getting embellished has to be flat, smooth, and dry, because any moisture, creases, and bumps can impact the transfer process. This is also why print shops avoiding printing designs on seams, zips, buttons, or across pockets – anything bumpy, basically.
Next it’s time to place the printed design onto the t-shirt, check it’s in the right position one last time, and start the transfer.
Step Four: Bring the Pressure
The press isn’t just resting on top of the t-shirt, it’s forcing the hot design into the fabric. How much force it uses varies based on the heat transfer material.
As with the heat settings, pressure is a delicate balance. Too low, and the design won’t adhere to the product, or it will peel off after a few washes. Too high, and it can create a press box, which is the outline of the press pressed into the fabric. This will probably wash out if the item is made of cotton or high cotton blends. But polyester, diva that it is, is less forgiving, and that “SAVE THE OWLS” t-shirt is going in the bin.
High pressure can also affect the transfer itself. It can smoosh the glue out from behind the design, so it will be visible on the fabric. Or it can liquify the ink to the point that it oozes into the negative spaces you were counting on for a clear design. Suddenly, the owl looks like a hill, “SAVE THE OWLS” looks like “SNEPFOVL5,” and everyone at your charity walk for the Oregon Owl Preservation Society is very confused.
Step Five: Wait Some Seconds
How many seconds does the press need to press for? You get 10 (meaningless and nonredeemable) points if you said, it depends on the heat transfer type! Some heat transfer types only require short bursts of heat to activate the adhesive, while others take longer.
Even different varieties of the same heat transfer type can require pressing for different lengths of time. For example, multi-colored plastisol designs need longer than one that only uses one color.
The length of time heat transfer vinyl (HTV) needs to be pressed also varies depending on the HTV type. My extremely objective formula is, the more fun the HTV, the longer it takes to press. Glitter HTV = longer than plain (20 seconds compared to 10 seconds), while glow-in-the-dark HTV = longest of all (25 seconds).
Step Six: Peel Reveal
The exciting bit! The transfer paper/film is peeled off to reveal the design. Some heat transfers are hot peels, meaning they need to be peeled off while they’re still hot, and some are cold peels, which means waiting until they’ve cooled down before peeling.
Some transfer types (direct to film (DTF), we’re talking about you) have a Step 6.5: a brief second pressing, with a layer of Teflon paper between the heat press and the garment.
And there you have it, a SAVE THE OWLS t-shirt any concerned owl fan would be proud to own. Just 199 left to go!
Settings for Different Heat Transfer Types
Here are the heat, pressure, and time settings for four of the most common types of heat transfer. Bear in mind that different print shops swear by different settings, and they all swear that they’re right. If they’ve been doing it their way for a while and it works, they probably are right.
Heat transfer printing is one of those things you get better at the more you do it, as you get to understand the process and your particular equipment. Like baking, or using a new phone, or (I assume) flying spaceships. So this chart gives a general idea, which printers finetune through experience.
| Type of Heat Transfer | How it works | Temperature in Fahrenheit (F) | Pressure in Pound-force per Square Inch (psi) | Time |
|---|---|---|---|---|
| Direct to Film (DTF) | The design is printed onto polyethylene terephthalate (PET) film. Powder is added to the ink (“gelled”), and turns into adhesive under pressure and heat. | 300F to 330F | Medium to firm (30 psi to 60 psi) | 10 to 15 seconds |
| Heat Transfer vinyl (HTV) | Aka iron-on vinyl. Comes as a sheet of vinyl: The design is cut out and melted onto the fabric. Usually made of polyurethane (PU) or polyvinyl chloride (PVC). | 305F to 345F | Medium to firm (30 psi to 60 psi) | 10 to 25 seconds |
| Plastisol Transfers | The design is printed in plastisol — an ink made of liquid plastic — onto a special transfer paper. | 325F to 375F | Firm (60 psi) | 4 to 12 seconds |
| Sublimation Printing | The design is printed in sublimation ink onto sublimation paper. Under heat and pressure, the ink transfers into the fibers of the product. Only works on polyester and only on light colors. | 375F to 410F | Medium (40 psi) | 35 to 55 seconds |
The Bottom Line
Wow, you read all the way down here? Nice one. Having read this entire article, we hope you feel like you could hot press a design onto a t-shirt – but it seems like a lot of effort so you’d rather have us do it.
Natasha Lavender
Natasha is an experienced writer and editor who has covered topics including technology, health and safety, business, and pop culture. Her work has been published by Good Housekeeping magazine, Forbes, Success, and more.
