On these pages we present a knowledge base essential for every professional applicator. You will also find application tips and technical data for the materials here.
Printing techniques
Flex – this is the most durable method of application on textiles. A thin polyurethane film available in many colors. Graphics are cut with a cutting plotter according to a design prepared as curves (vector graphics). After weeding (removing) the unwanted parts, only the actual graphic remains on the backing, i.e. the carrier film. Placed on the garment and subjected to the pressure and temperature of a heat press, the adhesive contained in the film is activated and the graphic bonds to the substrate. Such an application is resistant to detergents. If the print is not mechanically damaged, the application is practically indestructible. It is one of the easiest and least expensive marking methods to use. Many film colors, various effects and a wide range of decorative finishes are available >> flex film <<
Flock – a thick, velvety film. Flock printing is performed in the same way as with flex film. Flock creates a pleasant-to-the-touch application that is very durable and resistant to washing. Many colors and effects are available, such as glitter, camouflage and fluorescent colors... Combining two heat transfer techniques >> flex and flock << produces very interesting effects.
Sublimation – a technique for transferring graphics printed on sheets using special sublimation inks. These inks are very similar to water-based inks (their chemical composition differs only slightly). The print, made as a mirror image, is transferred from sublimation paper onto a polyester substrate using a heat press. Graphic applications can only be made directly on polyester; for other substrates such as cotton or cotton/polyester blends, suitable primers are required (coatings that absorb sublimation inks). Sublimation is a very durable and inexpensive technique. All that is needed to make a print is a suitably modified inkjet printer and sublimation inks.
DTG – digital direct-to-garment printing (Direct To Garment). A relatively durable technology, though not easy to use. Special inks are transferred directly onto the fabric. Ideal for printing on cotton, even dark cotton – this is made possible by printing with white ink. The only limitation is the price of a plotter using this technology. DTG requires considerable experience because the printing process consists of several stages (preparing the knitwear, printing, drying and heat setting), but it produces satisfying results, especially when printing tonal gradients. DTG is becoming an alternative to flex films printed with solvent or latex inks.
Screen printing – a proven technique for printing on any substrate. The durability of the graphic depends on the quality of the inks used. However, it is economical only for larger production runs, because the most labor-intensive stage is preparing the screen/film artwork used to create the pattern. The finished pattern is then reproduced – any number of colors can be applied using this technique. Graphic precision is limited, however, by the mesh density of the screen.
What we need to get started
Press (heat transfer press, transfer press) – a device for thermally transferring graphics onto textile substrates. It consists of a table and a heating plate that is lowered onto the material. Fully manual presses are available on the market – closing and opening are done by hand, and such a press has only a timer and temperature sensor; semi-automatic presses – closed manually but opening automatically after the specified time; and fully automatic presses – where the entire process is controlled electronically.
A very important element of a heat transfer press is the heating plate – it is the heart of the device. The plate must remain perfectly flat and heat evenly across its entire surface. If it deforms or develops burned-out areas, it can cause heat transfer film to peel off, sublimation graphics to transfer out of focus, or delicate materials to scorch.
Plotter – the basic device for cutting film, both flex and flock for heat transfers and ordinary self-adhesive plotter films. Many types of such devices can be found on the market - from inexpensive Chinese plotters to branded units that are considerably more expensive but offer the reliability of equipment from reputable manufacturers. Precision is the key to success here – even micron-scale uncut areas cause problems during subsequent material processing. Branded devices can operate for years without the slightest fault, while cheaper ones sometimes cannot operate correctly for 12 months.
Accessories – the most important is a sharp plotter blade. Professional companies should have a set of plotter blades (37-45° for flex film and 60° for flock film)
Press pillows – these pillows make application easier in difficult areas (collars, buttons on polo shirts, zippers on sweatshirts). A pillow placed under the material absorbs unevenness and makes the upper layer smooth and flat.
Weeding tools – a simple tool that makes weeding film easier. After cutting with a plotter, the pieces of film that are not wanted in the graphic must be removed. A properly shaped tip makes it easy to catch even the smallest elements.
Teflon sheets – protect the heating plate. To prevent adhesive or ink residue from reaching the plate and staining subsequent T-shirts, we recommend always using such protective sheets.
Squeegee – a very simple yet indispensable tool. If application tape is to be placed over a layer of film, the air between the two layers must be removed. This is where a squeegee is useful: thanks to its perfectly smooth edges, it allows this to be done quickly and easily.
Which textiles can heat transfer applications be applied to?
Essentially all commonly used textiles. From the most popular cotton and cotton blends, through knits and fabrics containing significant proportions of synthetic fibers (cotton with elastane, viscose, nylon), all the way to completely synthetic nylon knits and fabrics - from rigid polyesters to very elastic Lycra. Successful application depends on choosing the correct material: most flex and flock films are suitable for cotton, while specially dedicated flex films should be used for synthetic materials.
How should textiles be prepared for heat transfer?
For flex and flock heat transfer techniques, there are no special rules for preparing substrates. It is essential to remember to pre-press the material to remove finishing agents applied during production - mixtures of chemicals that prevent garments from being damaged during transport but can also significantly hinder proper film application. Insufficient pre-pressing of, for example, T-shirts before applying flex film often results in the film coming off, even before the first wash.
Sublimation techniques require different preparation. Sublimation is intended only for polyester substrates, so T-shirts should be made entirely of polyester. A number of processes can be used to enable this type of printing (for example, using film for sublimation printing - e.g. Subliflock, or using special cotton primers that enable direct printing)
What do the terms HOT PEEL and COLD PEEL mean?
This is important information for operators producing larger quantities of applications. After heat-applying the film under precisely specified conditions, which differ for each type of film, we remove the carrier layer (the layer that allowed us to position the flex film on the T-shirt). Hot peel means that the carrier layer can be removed almost immediately after opening the press (usually after approx. 3 seconds it can already be safely grasped). Cold peel means removing the carrier layer after it has cooled. It is worth noting that manufacturers do not follow one universal standard; films with carriers removed warm are often described as Hot peel. Stahls follows the rule that hot peel films are only those whose carrier can actually be peeled while hot - e.g. Premium Plus, while carriers peeled warm, e.g. Sports Film, are described as cold peel.
How to save a failed print - using a Cobra-type remover.
We often receive questions from customers about the availability of liquid for removing flex film. We wrote about the reasons for discontinuing distribution of this product on our Facebook page:
Despite many restrictions, responsible users can still use this liquid. The former Cobra is simply dichloromethane (methylene chloride), which can be purchased at low prices from specialist chemical supply centers. Using liquid to remove flex film is relatively hazardous, so we recommend taking particular care. The way the liquid works can be seen in the Stahls instructional video below: