Printing a heat transfer film with a latex inks in many cases is as easy as printing a pressure sensitive vinyl. Before you go into production, you will need to do some testing. As I like to tell people, Test, Don’t Guess.
The type of film that you will need is a heat transfer film designed for digital printing. The film should have a polyester or co-polyester release liner. This is important. The reason is that these types of release liners are much more stable when exposed to heat than a paper liner.
When I first tested the printability of the polyurethane film shown below, we were using the HP Designjet L25500 latex inkjet printer. The profile we used was a generic ‘heat transfer media’ profile. Printing a low resolution image from the internet our results with this stock profile were phenomenal.
Make sure that you print on the polyurethane film and not on the clear polyester carrier. This has happen to even experienced printers many times. Both the film and the release liner are very similar in appearance. The polyurethane side of the film typically has a matte finish. The carrier, on the other hand, has a smoother finish. If you are still confused which side is which, scrape a corner of the film with an Xacto® blade. The white polyurethane film is very thin and stretchable. The thicker polyester carrier is clear and will not stretch at all. Also when you are printing on the film, print “right reading”.
Test, Don’t Guess
The results that you achieve will depend on the material that you are printing on and the environment in your shop. Another major difference is the printer itself. Temperature settings used in printing a heat transfer material can vary from one printer to another. For example, the temperature settings for the HP Latex 360 printer can be significantly higher than the settings for the HP L25500 or the L26500 printers.
The reason that the HP 360 can print heat sensitive films at higher temperatures is that the curing system utilizes forced hot air to dry the media. Inside the curing module hot air is circulated and blown through hundreds of tiny nozzles onto the print media. The micro-jets of hot air are hot enough to cure the ink but not so hot as to deform or damage the substrate. The bottom line is that the curing temperature is higher, but the exposure to heat is lower.
The type of printable heat transfer film selected for a job is major factor regarding curing and drying temperatures and drying times. Settings when printing vinyls, polyurethanes and polyurethane blends can vary greatly.
Drying times for different films can also vary. Some heat transfer materials may take longer to dry completely. While a print may feel dry to the touch, an ink can take an additional ten minutes to a half hour to fully dry. If the ink has not dried completely, the masking used to transfer the applique may not stick sufficiently.
Prior to production, my advice is to evaluate the printability of the heat transfer material in the conditions within your shop. If you don’t achieve acceptable results, you will need to adjust your settings.
In modifying the settings when printing heat transfer vinyl films, my recommendations are the same as when printing many vinyl films.
Curing Temperatures of Latex Inkjet Printers
A standard setting for curing temperature when printing vinyl with an HP latex printer is 100°C to 110°C. In many cases that may be too hot for the heat transfer film that you are printing. In these cases, many printers will lower the heat setting to 88°C.
The lower temperature setting eliminates any problem with the film buckling or tunneling. When printing at the lower temperatures, the ink may not be completely dry. To compensate for this you need to make additional adjustments.
In changing the printer settings, increase the pass rate to 12 pass or 16 pass. You may also need to change from bidirectional printing to unidirectional. These adjustments will allow the print more time to cure at the lower temperature setting. You may also need to increase air flow to improve drying.
- Print Mode: 12 pass or 16 pass unidirectional
- Curing Temperature: 88°C
- Drying Temperature: 50°C
- Heating Air Flow: 45%
Unidirectional or Bidirectional
When you are printing unidirectional, you are only printing when the printhead is moving in one direction. In bidirectional printing, the printhead is printing as it moves back and forth. Obviously, bidirectional printing is much faster.
Bidirectional printing is, in most cases, acceptable for typical applications. Most customers will not discern a difference in print quality. If you want to be really picky, there is in fact a difference, slight though it may be. In bidirectional printing the printhead will print CMYK in one direction, but when travelling in the other direction it is printing KYMC. In some cases, this results in a slight color shift.
When printing with a latex printer, hopefully you will have the same success that we achieve printing with a stock “out-of-the-box” profile. Using a printable polyurethane film, we didn’t need to adjust the standard settings at all. We just loaded the media and printed.
Other printable heat transfer media may require tweaking of the profile. In some cases you will need to print at lower curing temperatures, such as 88°C. If the print does not dry properly, I suggest printing at a higher pass rate and using a unidirectional setting. Using these settings, printing will be slower, which allows the ink more time to dry. With a print that is completely dry, you can generally mask the printed applique after 30 minutes.
Using the suggested settings, you will sacrifice some printing speed. What you will gain, however, is a higher quality print that you can mask and heat press shortly after printing.
If you have a latex inkjet printer, you can decorate t-shirts, jackets and jerseys with colorful graphics and corporate logos using SEF Tatoo printable polyurethane heat transfer films. Selling printed appliques to your existing customer base is a great way to increase your shop’s sales at high profit margins without a lot of effort. The manufacturing process is not very complicated, so there is not much to learn. What you will need is a heat press machine.