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Heat Transfer Technology in Review

Josh Ellsworth

Josh is the VP of sales, dealer channel for Stahls'. He deals in the sales and implementation of heat-applied, apparel-decorating systems with a focus on customization. He holds skills in the production, sale, and marketing of customized apparel. He presents seminars at trade shows and contributes articles to trade publications, like Printwear magazine.

The term “transfer paper” is placed in a search engine more than 100,000 times globally per month. Heat press is searched for 60,500 times. The interest in being able to digitally print images onto paper and transfer them onto a textile or other surface is strong—trends of search volumes suggest, stronger than ever. When categorizing the output options for print media you end at inkjet and laser. Each basic technology has subsets—for instance, inkjet printing technology can utilize a number of inks such as aqueous, solvent, eco-solvent, sublimation or, more recently, latex or sepiax. When evaluating print devices, the ink or toner type and even brand is paramount to durability. Likewise, so is the paper technology. With the number of choices and manufacturers, results are all over the board when it comes to print vibrancy, color retention and durability in laundering.

Papers for light colors have recently made strides and are available in “scissor free” versions. With this technology, only the areas of the paper printed with toner transfer to the garment. This process represents a huge breakthrough in technology. (All images courtesy the author)

The simple, fast check list when evaluating any digital print paper or media is as follows:

1. It needs to print without jamming.

2. It needs to transfer adequately.

3. It needs to wash as expected for its intended use.

Diving further into the third item on the checklist, washing as expected for its intended use suggests that an understanding of possible uses is important. A family reunion shirt, a teddy bear T, a sports uniform and a corporate promo product all have different durability expectations. Therefore, it’s important to understand how each technology matches up. Likewise, it’s important to understand where demand is in order to invest and produce according to the best possible fit.

Aqueous inkjet papers

Aqueous inkjet transfer papers are perhaps the most popular. This is in large part due to the availability and inexpensive costs of inkjet print devices utilizing this type of ink. A basic printer can be purchased for under $100. Inkjet transfer papers for these printers come in two basic varieties—those for lights and those for dark color fabrics. The light color papers are simply paper backing and a polymer top coat with adhesive. In contrast, the dark color papers actually consist of two, usually separable layers, of paper backing and a white thin film coated with adhesive. These two layers are required for opacity. 

Inkjet transfer papers for dark-color fabrics consist of two, usually separable, layers of paper backing and a white thin film coated with adhesive. These two layers are required for opacity.

When printing and heat applying with either of these styles, a large square box the size of the sheet also transfers onto the garment. In order to avoid this, box trimming around the paper with scissors is necessary. This step can be automated for dark color papers by putting to use an optical eye vinyl cutter. These units are now available at price points in the $700 range. Keep in mind that designs/art for cutting need to be in vector format. 

How it works, basically, is users print an image with special registration points, load the printed paper into the cutter and then send the cut vector file from the same page from which that image was printed. The cutter does the work. These steps are necessary for each sheet. After trimming, excess white film is removed and the print is pulled off of the paper backing for heat application. 

For single-piece designs such as a square cut or a circle, you can usually lift the image and position it by hand. For intricate designs or those with free floating areas, a transfer mask is recommended to keep all elements in perfect registration. This can be a time-intensive process, but for personalized shirts, it works. Unfortunately, for light-color papers, the layers usually aren’t separable, meaning they can’t be trimmed on a cutter, leaving only hand-trimming as an option.

Laser papers

Just as with inkjet papers, laser papers come in varieties for light-color fabrics and those for darks. The dark papers are just like the inkjet papers and require trimming by hand or with an optic eye vinyl cutter. The development that catapults laser technology over inkjet is that papers for light colors have recently made strides and are available in “scissor free” versions. With this technology, only the areas of the paper printed with toner transfer to the garment. This process represents a huge breakthrough in technology. 

With solvent printing, the single biggest selling point is the durability. When matched with the proper media, this ink type can produce prints that outlast the garment. Most major manufacturers offering personalization on promotional products, bags, athleticwear and so on employ solvent print technology, and some are successfully experimenting with compatibility of latex print devices with these same media types.

In order to utilize this breakthrough, it’s important to purchase a printer that is compatible with this type of paper. Many low-end, inexpensive laser printers do not offer the same durability in washing or the same conveniences of being able to feed this style of paper without jamming. These same papers offer unique opportunities for transferring foil onto light or dark colored garments since, when combined the paper, the foil provides opacity.

Solvent printing

Large-format digital printing is more popular than ever. Sign companies that have invested in wide-format devices for signs are sitting on a gold mine for fabric applications. Most of them don’t even know it. There is a wide array of solvent or eco-solvent print/cut materials compatible with these printers for heat transfer. Once again, there are products for light colors and those for dark colors. 

With solvent printing, the single biggest selling point is the durability. This ink type, when matched with the proper media, produces prints that outlast the garment whereas the previous two print technologies produce prints that begin fading after a couple dozen wash cycles. 

Solvent printers are fed by the roll instead of the sheet and, often times, with a print/cut device, the machine can be programmed to automatically cut around each image. This results in a huge savings in labor for higher-volume customization. 

Most major manufacturers offering personalization on promotional product items, bags, athletic wear and so on employ solvent print technology. Some are now experimenting with compatibility of latex print devices with these same media types with success.

Sublimation

Sublimation printing has been around for some time and continues to excel on polyester-based applications. The process involves loading a compatible inkjet printer, laser printer or wide format printer with sublimation inks, then printing on a sublimation photo paper and transferring to a garment. When it comes to fabric color compatibility, this process is only good for lights, as the ink actually dyes the fabric. It simply doesn’t show up on darks. On lights, however, it offers a great, durable solution. Note that for sublimation the fabric needs a high percentage of polyester for the dye process to be successful. 

Digital print technology is growing. Regardless of the item, heat presses are applying the solution. When planning to offer digitally printed designs, be sure to invest in a print technique that meets the customer’s requirements.