How to Prevent Heat Marks on Heat Sensitive Textiles

If you’ve been keeping up with the Siser® Blog you now Siser HTV can be applied to all kinds of materials and textiles. Including acrylic, triblends, fleece, and even cardstock! While we enjoy testing the limits of Siser products, we also encourage you to experiment with innovative uses for Siser HTV. Many of you have been trying out application on all kinds of substrates which we think is awesome! A common question we receive is how to apply on items that include “Do Not Iron” or “Cool Iron Only” on the tag. (These tips will also work for applying on heat sensitive fabrics like rayon, 100% polyester, silk, or any other material you’re unsure about.)

Cool iron tag on heat sensitive polyester scarf

My first piece of advice is…

Tip #1: Don’t Apply Unless You Have An Extra to Spare

If the tag specifically calls “No Iron” or “Cool Iron Only” it’s most likely because the material will discolor under high heat. Sometimes the discoloration is temporary. Other times it’s permanent. If you have a project you really want to do and you’re willing to run the risk of irreversibly ruining the item, it’s best to have at least one duplicate item as a back up. However, if you’re in a pinch, you can test press an inconspicuous area of the garment like inside on the back.

Polyester with carrier marks

Note the darker box shapes left behind from the carrier after pressing with high heat.

Tip #2: Use a Heat Press

Did you know most iron settings are actually a range of temperatures? When you hear the little tick from the iron you know you’ve reached the highest temperature in your setting and it will cycle back down to the lowest temperature in the setting. For most projects the variance in temperatures is not a problem, but when working with heat sensitive fabrics the regulated, accurate temperature on a heat press is your best bet. Additionally, achieving proper pressure with your home iron is not as accurate as a heat press. Proper pressure is important for every project, but especially when we’ll be reducing another part of the application process. Which brings me to tip #3!

Do not use a home iron on heat sensitive materials

Tip #3: Lower Your Temperature

The great thing about Siser materials is that most of them can be applied at the low temperature of 280°F! Many competitor materials require higher temperatures that restrict your application options. Our heat application settings, listed on the Siser website and App, are what we suggest for best application, but they can be adjusted to fit your project. There’s still a chance the material won’t react well to the heat, but that’s why having an extra to spare is tip #1!

Heat pressing StripFlock to heat sensitive polyester at 280°F

Tip #4: Increase Your Dwell Time

Since we’ve lowered the temperature we need to increase the amount of time the material receives heat. This will help fully set the heat transfer vinylStripFlock® typically takes 15-20 seconds so I pressed for 25-30 seconds. StripFlock requires you to wait until the carrier sheet is cool before peeling it. You’ll feel some resistance as you peel. That’s normal due to the fuzzy texture releasing from the pressure sensitive carrier.

Peel Stripflock's carrier mask when it's cool to the touch

Tip #5: Use A Cover Sheet

We always recommend using a heat transfer cover sheet for all your presses. However this heat barrier is especially important when pressing heat sensitive materials. Heat transfer cover sheets offer delicate textiles a layer of protection from the hot upper platen. If you’re working with an especially sensitive fabric, you may want to use parchment paper as your cover sheet since it releases heat the quickest. If you don’t have a non-stick cover sheet or parchment paper then you can use shiny side of multipurpose paper or a clean, cotton pressing cloth.

With these few tips in mind you can create awesome projects with Siser HTV- like this cute birds in flight scarf!

DIY bird scarf with StripFlock heat transfer vinyl

A heat sensitive fabric project with StripFlock HTV

If you have any questions about this post please leave them in the comments!

Want to watch these tips in action? See how the lower temperature application method works in the video below: