Silk Screening

Silk Screening is a form of screen printing. Screen printing is a printing technique that uses a woven mesh (such as silk, polyester, nylon, etc.) to support a stencil through which ink is forced to the surface (such as fabric, paper, etc.) below the screen. An ink-blocking stencil is attached to the woven mesh which allows a design to be printed in the non-blocked area of the screen. Ink is applied to the screen and a squeegee or roller is moved across the screen stencil, forcing ink through the threads of the woven mesh the are not blocked by the stencil to the surface below.

Screen printing is more versatile than traditional printing techniques. The surface does not have to be printed under pressure, and it does not have to be a flat surface. Screen printing inks can be used to work with a variety of materials, such as textiles, ceramics, wood paper, glass, metal, and plastic.

Traditionally, production garment decoration has relied on screen printing for printing designs on garments including t-shirts. Today, garments are printed using specially designed inkjet printers. Screen printing, however, has remained an attractive, cost-effective, and high production-rate method of printing designs onto garments.

There are various terms used for what is essentially the same technique. Traditionally the process was called screen printing or silkscreen printing because silk was used in the process. Today, synthetic threads are commonly used in the screen printing process. The most popular mesh in general use is made of polyester. There are special-use mesh materials of nylon and stainless steel available to the screen printer.

History

Screen printing first appeared in a recognizable form in China during the Song Dynasty (960–1279 AD). Other Asian countries adopted this method of printing and advanced the craft.

Screen printing was largely introduced to Western Europe from Asia sometime in the late 18th century, but did not gain large acceptance or use in Europe until silk mesh was more available for trade from the east and a profitable outlet for the medium discovered.

Screen printing was first patented in England by Samuel Simon in 1907. It was originally used as a popular method to print expensive wall paper, printed on linen, silk, and other fine fabrics.

Graphic screen printing is widely used today to create many mass or large batch produced graphics, such as posters or display stands. Full color prints can be created by printing in four colors - CMYK (cyan, magenta, yellow and black ('key')). Screen printing is often preferred over other processes such as dye sublimation or inkjet printing because of its low cost and ability to print on many types of media.

Printing Technique

A screen is made of a piece of porous, finely woven fabric called mesh stretched over a frame of aluminum or wood. Areas of the screen are blocked off with a non-permeable material to form a stencil, which is a negative of the image to be printed; that is, the open spaces are where the ink will appear.

The screen is placed atop a substrate such as paper or fabric. Ink is placed on top of the screen is used to fill the mesh openings with ink. The operator spreads the ink over the screen filling the mesh openings with ink. The operator then uses a squeegee (rubber blade) to move the mesh down to the substrate and pushes the squeegee to the rear of the screen. The ink that is in the mesh opening is pumped or squeezed by capillary action to the substrate in a controlled and prescribed amount. As the squeegee moves toward the rear of the screen the tension of the mesh pulls the mesh up away from the substrate (called snap-off) leaving the ink upon the substrate surface.

Stencil Techniques

There are several ways to create a stencil for screen printing An early method was to create it by hand in the desired shape, either by cutting the design from a non-porous material and attaching it to the bottom of the screen, or by painting a negative image directly on the screen with a filler material which became impermeable when it dried. For a more painterly technique, the artist would choose to paint the image with drawing fluid, wait for the image to dry, and then coat the entire screen with screen filler. After the filler had dried, water was used to spray out the screen, and only the areas that were painted by the drawing fluid would wash away, leaving a stencil around it. This process enabled the artist to incorporate their hand into the process, to stay true to their drawing.

A method that has increased in popularity over the past 70 years is the photo emulsion technique:

1. The original image is created on a transparent overlay such as acetate or tracing paper. The image may be drawn or painted directly on the overlay, photocopied, or printed with an inkjet or laser printer, as long as the areas to be inked are opaque. A black-and-white positive may also be used (projected on to the screen). However, unlike traditional platemaking, these screens are normally exposed by using film positives.
2. A screen is then be selected. The screen is coated with emulsion and let to dry in the dark. Once dry, the screen is ready to be burned/exposed.
3. The overlay is placed over the emulsion-coated screen, and then exposed with a light source containing ultraviolet light. The UV light passes through the clear areas and create a polymerization (hardening) of the emulsion.
4. The screen is washed off thoroughly. The areas of emulsion that were not exposed to light dissolve and wash away, leaving a negative stencil of the image on the mesh.

Types of Inks

Discharge inks are used to print lighter colors onto dark background fabrics, they work by removing the dye in the garment – this means they leave a much softer texture. They are less graphic in nature than plastisol inks, and exact colors are difficult to control, but especially good for distressed prints and underbasing on dark garments that are to be printed with additional layers of plastisol.

Glitter/Shimmer metallic flakes are suspended in the ink base to create this sparkle effect. Usually available in gold or silver but can be mixed to make most colors

Gloss is a clear base laid over previously printed inks to create a shiny finish.

Metallic is similar to glitter, but smaller particles suspended in the ink. A glue is printed onto the fabric, then nanoscale fibers applied on it.

Plastisol is the most common ink used in commercial garment decoration. Good color opacity onto dark garments and clear graphic detail with, as the name suggests, a more plasticized texture. This print can be made softer with special additives or heavier by adding extra layers of ink. Plastisol inks require heat (approximately 150°C (300°F) for many inks) to cure the print.

PVC and Phthalate Free are relatively new breed of ink and printing with the benefits of plastisol but without the two main toxic components - soft feeling print.

Water-Based inks penetrate the fabric more than the plastisol inks and create a much softer feel. Ideal for printing darker inks onto lighter colored garments. Also useful for larger area prints where texture is important. Some inks require heat or an added catalyst to make the print permanent.

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