Digital Decorating: Heat Transfer

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In this ever-changing world, consistency is key when it comes to applying heat transfers to any substrate. Using a reliable, durable and calibrated heat press is your most important tool when producing custom quality images with heat transfers.

Use a quality calibrated heat press
There are many heat presses on the market that may look good as far as price, but when you buy it and use it a few times, you start seeing inconsistencies. It is best to research heat presses before purchasing. The three most important things to remember about a heat press are time, temperature and pressure. All three key factors are provided when you purchase heat transfers from any transfer manufacturer. It is important you follow these application instructions or at least start with the instructions and adjust if needed:

Time – Time is hard to make a mistake, as long as your press can count down, you will be okay.

Temperature – Temperature is a bit tougher to calibrate. There are three easy tools to use to check the temperature of the heating element on your press.
• A temperature gun is the first example but it won’t always be accurate. Temp guns can sometimes be off by 10 or 20 degrees! This may not seem a big problem, but often it can be the differentiator between success and failure.
• Thermo strips work well, but you have to discard them after one use.
• My preferred temperature measuring tool is a surface probe. This tool is the most precise and accurate in my opinion, due to the direct contact with the heating element. You can reuse the probe as many times as you need too.

Pressure – When it comes to pressure, the question is do you have a manual or an automatic/pneumatic heat press? A pneumatic press has an air pressure gauge, which you can measure and control the pressure. Most manual presses will not have this gauge. If you are working with a manual press that does not have something to measure the amount of pressure, you will have to rely on the “feel.” Or assistance from the manufacture of the heat press to provide you with their method for measuring pressure on manual equipment.

Know your material
The more you know about the substrate you are fusing onto, the better. In today’s market, consumers want a transfer that will work on any substrate/material. We have a long way to go until we get there. For now, customizing a transfer product for your substrate will get you the best result on your desired material. The first thing to consider is the fabric content.

Heat transfer manufacturers will provide you with heat transfer product recommendations for different materials when asked. Here are some fabric characteristics to consider:

Polyester – If applying to 100% polyester or a material that contains a large amount of polyester, consider using a product with the ability to block dye migration.

Stretch – Second, think about the way the fabric stretches. Make sure you have a stretchable transfer for a stretchable fabric. Otherwise, it is possible the transfer will crack when stretched or washed.

Durability – If the material does not have any stretch or is used for work or industrial applications, durability is always a good default to fall back on.

Heat Sensitivity – Always test the heat transfer you will be using on the fabric being used before starting production but first see how much heat and pressure the fabric can withstand before there is a change in the fabric’s appearance. Once you know your limits, results should be consistent as long as the protocols are followed.

Preheating – Preheating your garments before application can ensure you are going to get a strong bond between the fabric and the transfer. When preheating, you are driving moisture out of the garment. A high moisture content in the fabric can adversely affect the bond between the fabric and the transfer. Preheating the fabric for only for 3-4 seconds should suffice.

For example, when fusing a puff transfer, make sure you drive out as much moisture as possible. If there is moisture in the garment before you apply the puff transfer, you might end up with an image which does not have the appearance you are looking for. The image might have a rough texture, the embossment might be a bit uneven or you may experience poor adhesion. So, when in doubt, preheat your garment.

Screen printed heat transfer storage – avoid moisture at all cost
Storage – The storage of your heat transfers is very important. For most heat transfers, storing in a cool dry temperature- regulated area is the best way to insure consistent application performance of your heat transfers. Keep the transfers in a sealed air tight container/zip lock bag to block moisture from absorbing back into the transfers.

Moisture – Too much moisture in a heat transfer can result in poor adhesion and can also create craters/pock marks in the applied graphic. If you are running into this issue, try this easy step to evaporate the moisture from your transfers: drive the moisture out with heat. You don’t want to go too high in temperature, 150°F for about 10 to 15 minutes should be sufficient. It is best to do this technique in a sealed box or even a standard home oven.

If you have a screen-printing shop, a conveyer dryer is the fastest way of driving the moisture out of your transfers. For this tip, you want your temp a little higher and dwell time a lot faster (Temp: 250°F/121°C, Dwell: 25-30 seconds). Do not over extend the duration of these techniques. It may result in poor release from the carrier or poor durability.

Using a cover sheet when applying a heat transfer
Heat press application tools and hacks are your friends. However, be weary of some techniques you may find online. I’ve seen many “tips” online that were incorrect or grossly incorrect. The more accurate you can be the better you can provide a consistent quality product to your customers. You can even say that in some cases you are only as good as the tools you use.

Teflon sheets, parchment paper or any material you use to help fuse heat transfers to a garment are very useful tools. When using any of these above-mentioned materials as a cover sheet, keep in mind that you will want to raise the temperature and even the dwell time of your application settings slightly. The reason is because the cover sheet will cause the temperature to drop a little bit and it will take longer for your heat press to get up to temp during the application process.

Quick application tip – When applying transfers to heat sensitive fabrics like 100% polyester or polyester blends that will scorch from the heating element on your heat press, use a thin piece of polyester fabric or even a piece of cotton fabric as a cover sheet. This technique will protect the fabric more than a Teflon sheet or parchment paper.

Again, be sure to calibrate your temperature accordingly when adding the extra fabric as a cover sheet. This is where the surface probe can shine. First take your fabric and place one layer over the contact point on your surface probe. Then take the temperature reading and see how long the press takes to get up to temp. If it takes three seconds, extend you application dwell time an extra three seconds. If it takes five seconds, adjust accordingly. This tip also can help eliminate that dreadful carrier box.

Sean Savitch is a research and development specialist for Insta Graphic Systems. He has been associated with textile printing for more than 20 years, working with innovative applications and new technologies in large print shops throughout North America. To read more of Savitch’s work, visit the company’s blog at instagraphicsystems.wordpress.com. For further information, please contact Sean Savitch at seans@instagraph.com.