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It’s common knowledge that the formula for properly applying a heat-applied graphic is temperature, time, and pressure. In most modern heat press machines, temperature and time have long had digital displays that make it relatively easy to set the dial to the correct number.
In recent years, newer heat presses have offered a digital gauge for pressure. If you have an older machine without a pressure gauge, determining the proper amount of pressure is done solely by feel or muscle memory. It is adjusted by how hard the operator presses down on the handle when the upper platen is brought down on top of the lower platen.
As you can imagine, the amount of force applied by someone 6' 2" tall and weighing 210 pounds is going to be different than a 5' 4" person weighing 125 pounds. Hence, the right amount of pressure can be a combination of experience gained from trial and error and perhaps even a little bit of luck.
Combine that variable with the fact that many times a heat press is used by a variety of operators in a shop, each with their idea of what proper pressure is. This creates a scenario where ensuring that the proper pressure is consistently applied throughout a production run or in a variety of jobs within the same day to be low.
So, when using the trinity formula, pressure is the trickiest of the three to conquer.
Higher-end presses with a pressure gauge will typically have a range of between one and nine. One through three is light pressure, four through six is medium pressure, and seven through nine is regarded as heavy pressure. The digits can sometimes be misleading. However, it does make the process repeatable.
The right amount of pressure directly affects the quality of the finished product you are adhering a decoration to. If you use too much pressure, it can drive the ink far into the garment or substrate, which will dull the vibrancy of the colors.
Too much pressure also wears out the operator. The longer the run, the more tired the worker will get, which, over time may cause them to apply less pressure than at the beginning of their shift or the run, creating inconsistency in the look of the finished products.
Thirdly, there’s no quicker way to shorten the lifespan of your heat press than to apply too much pressure repeatedly.
Too light of pressure has its negative consequences as well. If pressing a cotton shirt, for example, one of the objectives when heat pressing a shirt is to smooth out wrinkles and flatten down the fibers. Sometimes, when enough pressure is not applied, the fibers will stick up through the transfer giving the design a fuzzy or worn look.
You also run the risk of the heat-applied graphic not properly adhering to the garment, which can result in it coming off in the wash.
The right amount of pressure drives softened agents into the shirt. When the press is programmed for the appropriate amount of time, the inks cure and are securely linked. This bond will normally outlast the life of the garment.
A variable that affects the amount of pressure needed for application is the thickness of the garment. In general, the thicker the substrate, the more pressure is needed. Most presses have an adjustment to allow for thickness, and the pressure should be tested while the garment is on the machine.
When the garment is 100 percent polyester, the smoothness of the fabric requires less pressure than with other materials. You also need to be careful because polyester is more prone to “bruising” or showing heavy pressure lines than a cotton/polyester blend.
What’s more, there are two ways to load a shirt onto the heat press platen, which can also affect the amount of pressure required. On a traditional heat press, the entire shirt is typically laid down on the lower platen. If there are seams, grommets, a placket with buttons, etc., special care must be taken that these are not going to interfere when the upper platen is brought down.
In recent years, some manufacturers have started offering what is called a threadable press. It has an open throat, which means that only one layer of fabric is placed on the lower platen while the rest of the shirt hangs down beneath the lower platen. You will not need as much pressure when heat pressing a single layer as you will when you are doing the entire garment.
Another way to get around the challenge of having the entire garment on the heat press is to use a smaller platen or one that is specifically designed for that product. Most manufacturers offer a selection of platens that can be exchanged with the original that came with the press.
Sizes are available for children’s and youth garments, womenswear, pockets, labels, and more. This allows you to drape only the portion of the item you want to decorate on the press while the excess hangs off the edges.
Every job has its unique set of variables, however, always start out by following the manufacturer’s recommended settings for the heat transfer product. Some tweaking may be necessary based on the specific fabric or blends you are decorating as well as the calibration of your brand of press. If it’s a garment and a heat-applied product you are not familiar with, it’s always best to test.
As far as the press itself, if you are buying equipment, a model with an over-the-center pressure floatation adjustment ensures the greatest accuracy and evenness across the platen. Some models adjust from the back of the heat press, and this may cause inconsistent pressure. This type has a rigid top and bottom that open and close like an alligator’s mouth. When pressure is uneven, the decoration does not completely adhere, and unbonded areas will later come off.
One way to test if pressure is uneven, other than noticing it in the resulting print quality, is to put a business or credit card in each corner of the machine. Lock the top platen down and proceed to pull out the card in each corner. If it’s easy to pull out the cards in the front, but hard to pull out the cards in the back, you’ve got uneven pressure. There isn’t a tool or measuring device to test this, it’s all done by feel.
For the technical types who like to know how things work, the pressure on the average heat press is determined by a linkage system, unless you have a semi-automatic. The linkage system has a fixed back, and the distance in between the linkage is adjusted. Air equipment is run from a pneumatic cylinder that is set to a predetermined pounds per square inch (PSI).
On a press that gets average use, the linkage system lasts a long time. It is all based on the amount of usage and if it is subjected to too much pressure on a regular basis. But, in general, most presses can do 100,000 hits or more before displaying any issues. If it is wearing out, you will notice looseness at the pivot points where the pins are located. It will resemble a door that has sprung its hinges.
The good news is that if the owner is mechanical, it is very easy to change out this part. Someone can either be walked through it on the phone or watch a video. If the owner is uncomfortable with attempting the replacement, the machine can be shipped to a repair center.
It pays to be educated about your equipment and follow application instructions. Machines and products have changed. While “the heavier, the better” may have been good advice 20 years ago, it no longer applies in today’s world. Instead, consider the fabric, substrate, and mechanics of your equipment to ensure the best results.