Transfer printing

 

Transfer printing

Transfer printing is the term used to describe textile and related printing processes in which the design is first printed on to a flexible nontextile substrate and later transferred by a separate process to a textile.

Where does transfer printing it come from?

Transfer Printing was first developed to embellish ceramics, not clothing. The technique was born around the 1750’s in England and quickly spread to other parts of Europe where it caught on. Back then the process involved a copper or steel plate or roller that was engraved with a decorative element. The roller or plate would have its surface covered with ink and later would be pressed or rolled over the desired piece. It wasn’t an easy procedure (or fun) by any means, but it was still quicker than hand painting and the result was similar enough.

Thermal Transfer Printing, which is the kind of technique mostly used today, didn’t come until much later. It was invented by a corporation called SATO during the late 1940’s in the US (Is it just me? Or does it kind of sound like an evil corporation from a comic book?).

What’s all the fuss about?

As with everything in life, Transfer Printing has its advantages and its disadvantages.

On the good side: It’s fairly simple (you don’t really need a master’s degree), the equipment is relatively inexpensive, especially when compared to DTG printers, and it can reproduce high quality, complex images. It is also one of the best techniques to use for full-colour prints.

On the bad side: It is slower than other procedures (still faster than hand painting, though), it’s got limitations onto which types of fabrics it can be printed; those sensitive to high temperatures are a no-no, and there might be some restrictions on the reproduction of darker shades.

It may be asked why this devious route should be chosen instead of directly printing the fabric. The reasons are largely commercial but, on occasion, technical as well and are based on the following considerations.

1. Designs may be printed and stored on a relatively cheap and nonbulky substrate such as paper, and printed on to the more expensive textile with rapid response to sales demand.

2. The production of short-run repeat orders is much easier by transfer processes than it is by direct printing.

3. The design may be applied to the textile with relatively low skill input and low reject rates.

4. Stock volume and storage costs are lower when designs are held on paper rather than on printed textiles.

5. Certain designs and effects can be produced only by the use of transfers (particularly on garments or garment panels).

6. Many complex designs can be produced more easily and accurately on paper than on textiles.

7. Most transfer-printing processes enable textile printing to be carried out using simple, relatively inexpensive equipment with modest space requirements, without effluent production or any need for washing-off.

Against these advantages may be set the relative lack of flexibility inherent in transfer printing: no single transfer-printing method is universally applicable to a wide range of textile fibres. While a printer with a conventional rotary-screen printing set-up can proceed to print cotton, polyester, blends and so forth without doing a great deal beyond changing the printing ink used, the transfer printer hoping to have the same flexibility would need to have available a range of equipment suited to the variety of systems that have to be used for different dyes and substrates using transfer technology.

In addition factors such as stock costs, response time and so on do not always apply and unlike dyers, most printers are able to operate without steaming or washing by using pigment-printing methods. Thus a balance exists which not only permits but even requires the coexistence of direct and transfer printing. The relative importance of the two methods consequently varies with fluctuations of the market, fashion and fibre preference.

A great many methods of producing textile transfer prints have been described in the literature. Many of them exist only in patent specifications but several have been developed to production potential. They may be summarised most conveniently as below.

Sublimation Transfer

This method depends on the use of a volatile dye in the printed design. When the paper is heated the dye is preferentially adsorbed from the vapour phase by the textile material with which the heated paper is held in contact. This is commercially the most important of the transfer-printing methods.

Melt Transfer

This method has been used since the 19th century to transfer embroidery designs to fabric. The design is printed on paper using a waxy ink, and a hot iron applied to its reverse face presses the paper against the fabric. The ink melts on to the fabric in contact with it. This was the basis of the first commercially successful transfer process, known as Star printing, developed in Italy in the late 1940s. It is used in the so-called ‘hot-split’ transfer papers extensively used today in garment decoration.

Film Release

This method is similar to melt transfer with the difference that the design is held in an ink layer which is transferred completely to the textile from a release paper using heat and pressure. Adhesion forces are developed between the film and the textile which are stronger than those between the film and the paper. The method has been developed for the printing of both continuous web and garment panel units, but is used almost exclusively for the latter purpose. In commercial importance it is comparable with sublimation transfer printing.

Wet Transfer

Water-soluble dyes are incorporated into a printing ink which is used to produce a design on paper. The design is transferred to a moistened textile using carefully regulated contact pressure. The dye transfers by diffusion through the aqueous medium. The method is not used to any significant extent at the present time.

These different methods are considered separately in this chapter since they introduce different scientific and technical factors, and their use is best discussed in the context of the rather different commercial environments.

What’s next for transfer printing?

We’re never quite sure about the technology of these techniques, but after seeing this video, everything might be possible. Some savvy people in Barcelona discovered a way to transfer prints using water.

Transfer Printing: Properly Explained

So to wrap this up let’s simply explain how Transfer Printing works. Let’s take a look at the different stages of transfer printing: 

Image selection

You can choose virtually any image for transfer printing. It’s way of transferring allows for both complex (with many colours) and simple (with a few colours) images to be printed. Thanks to the fact that the design is printed onto paper first instead of the garment, it allows for more intricate details to show when compared to DTG that may have a more “blurry” finish. As with any other printing technique, it is advised that the original file be a high-quality one (300 dpi) to ensure the best possible result.

Heat transfer

Once the design has been selected, it is printed on a special heat transfer paper (I told you there was magic involved) which is then positioned on the garment. The (magical) paper is later squashed against the fabric using a heat press. It is left this way for the amount of time is necessary for the heat to do its job. After the required amount of time has passed, the press if lifted and the garment is left alone to cool down. If everything went well, then you should have a quality finish t-shirt.

How does transfer printing it work?

Most professional T-shirt printers nowadays use a more sophisticated version of the simple iron-on method, but the basics are still the same. What happens is that the heat transfer machine releases the right amount of pressure, holds the garment in place and has a consistent temperature which allows the colour pigments to be transferred from one surface to the other. Heat transfer literally melts the image onto the fabric.

Heat Transfer Paper

It’s advisable to use commercial heat transfer paper as this will give the image a much better quality finish, lasts longer and won’t fade, bleed or peel. Cheap paper is not suitable for professional looking print since it is likely to show a line around where it’s cut and have that awful shiny finish, making the garment look very ‘homemade’.

 Benefits

•   Inexpensive
•  Good for small quantities
• Can print complex images with many colours and intricate designs
• Prints on any garment regardless of colour
• Easy for amateurs
• Clean (screen printing can be very messy)

Disadvantages

•  Not practical for large quantities
•  Not as flexible when it comes to printing on different kinds of materials
• Each design must be cut one by one

Heat transfer printing for small businesses

Heat transfer machines are relatively cheap, easy to use, lightweight and don’t take up much space. This kind of printing can be done on demand, eliminating the need for holding stocks or large print runs. Just print when people place orders, as opposed to printing, keeping garments in stock and hoping you’ll receive hundreds of orders. This can be beneficial for start-ups offering small quantities of specially designed t-shirts as there are virtually no extra costs involved.