Screen printing information

 

What is Screen printing?

Screen printing is a printing technique that uses a woven mesh to support an ink-blocking stencil. The attached stencil forms open areas of mesh that transfer ink or other printable materials which can be pressed through the mesh as a sharp-edged image onto a substrate. A fill blade or squeegee is moved across the screen stencil, forcing or pumping ink into the mesh openings for transfer by capillary action during the squeegee stroke. Basically, it is the process of using a stencil to apply ink onto another material.

Screen printing is also a stencil method of print making in which a design is imposed on a screen of polyester or other fine mesh, with blank areas coated with an impermeable substance. Ink is forced into the mesh openings by the fill blade or squeegee and onto the printing surface during the squeegee stroke. It is also known as silkscreen, serigraphy, and serigraph printing. A number of screens can be used to produce a multicoloured image.

Various Terms used for Screen printing

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 prior to the invention of polyester mesh. Currently, 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.

Encyclopedia references, encyclopedias and trade publications also use an array of spellings for this process with the two most often encountered English spellings as, screenprinting spelled as a single undivided word, and the more popular two word title of screen printing without hyphenation.

History of Screenprinting

Screen printing is a form of stenciling that first appeared in a recognizable form in China during the Song Dynasty (960–1279 AD). It was then adapted by other Asian countries like Japan, and was furthered by creating newer methods.

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.

Early in the 1910s, several printers experimenting with photo-reactive chemicals used the well-known actinic light activated cross linking or hardening traits of potassium, sodium or ammonium Chromate and dichromate chemicals with glues and gelatin compounds. Roy Beck, Charles Peter and Edward Owens studied and experimented with chromic acid salt sensitized emulsions for photo-reactive stencils. This trio of developers would prove to revolutionize the commercial screen printing industry by introducing photo-imaged stencils to the industry, though the acceptance of this method would take many years. Commercial screen printing now uses sensitizers far safer and less toxic than bichromates. Currently there are large selections of pre-sensitized and “user mixed” sensitized emulsion chemicals for creating photo-reactive stencils.

The Printer’s National Environmental Assistance Center says “Screenprinting is arguably the most versatile of all printing processes.” Since rudimentary screenprinting materials are so affordable and readily available, it has been used frequently in underground settings and subcultures, and the non-professional look of such DIY culture screenprints have become a significant cultural aesthetic seen on movie posters, record album covers, flyers, shirts, commercial fonts in advertising, in artwork and elsewhere..

Modern Advancements in Screen printing

Credit is generally given to the artist Andy Warhol for popularising screen printing identified as serigraphy, in the United States. Warhol is particularly identified with his 1962 depiction of actress Marilyn Monroe screen printed in garish colours.

American entrepreneur, artist and inventor Michael Vasilantone would start to use, develop, and sell a rotary multicolour garment screen printing machine in 1960. Vasilantone would later file for patent on his invention in 1967 granted number 3,427,964 on February 18, 1969. The original rotary machine was manufactured to print logos and team information on bowling garments but soon directed to the new fad of printing on t-shirts. The Vasilantone patent was licensed by multiple manufacturers, the resulting production and boom in printed t-shirts made the rotary garment screen printing machine the most popular device for screen printing in the industry. Screen printing on garments currently accounts for over half of the screen printing activity in the United States.

In June 1986, Marc Tartaglia, Marc Tartaglia Jr. and Michael Tartaglia created a silk screening device which is defined in its US Patent Document as, “Multi-colored designs are applied on a plurality of textile fabric or sheet materials with a silk screen printer having seven platens arranged in two horizontal rows below a longitudinal heater which is movable across either row.” This invention received the patent number 4,671,174 on June 9, 1987, however the patent no longer exists.

Graphic screenprinting 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 CMYK (cyan, magenta, yellow and black (‘key’).

Screen printing lends itself well to printing on canvas. Andy Warhol, Rob Ryan, Blexbolex, Arthur Okamura, Robert Rauschenberg, Roy Lichtenstein, Harry Gottlieb, and many other artists have used screen printing as an expression of creativity and artistic vision.

How Screen printing Is Done

A screen is made of a piece of mesh stretched over a frame. A stencil is formed by blocking off parts of the screen in the negative image of the design to be printed; that is, the open spaces are where the ink will appear on the substrate.

Before printing occurs, the frame and screen must undergo the pre-press process, in which an emulsion is ‘scooped’ across the mesh and the ‘exposure unit’ burns away the unnecessary emulsion leaving behind a clean area in the mesh with the identical shape as the desired image. The surface (commonly referred to as a pallet) that the substrate will be printed against is coated with a wide ‘pallet tape’. This serves to protect the ‘pallet’ from any unwanted ink leaking through the substrate and potentially staining the ‘pallet’ or transferring unwanted ink onto the next substrate. Next, the screen and frame are lined with a tape. The type of tape used in for this purpose often depends upon the ink that is to be printed onto the substrate. These aggressive tapes are generally used for UV and water-based inks due to the inks’ lower viscosities. The last process in the ‘pre-press’ is blocking out any unwanted ‘pin-holes’ in the emulsion. If these holes are left in the emulsion, the ink will continue through and leave unwanted marks. To block out these holes, materials such as tapes, specialty emulsions and ‘block-out pens’ may be used effectively.

The screen is placed atop a substrate. Ink is placed on top of the screen, and a floodbar is used to push the ink through the holes in the mesh. The operator begins with the fill bar at the rear of the screen and behind a reservoir of ink. The operator lifts the screen to prevent contact with the substrate and then using a slight amount of downward force pulls the fill bar to the front of the screen. This effectively fills the mesh openings with ink and moves the ink reservoir to the front of the screen. 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, i.e. the wet ink deposit is proportional to the thickness of the mesh and or stencil. 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.

There are three common types of screenprinting presses. The ‘flat-bed’, ‘cylinder’, and the most widely used type, the ‘rotary’.

Textile items printed with multi-colour designs often use a wet on wet technique, or colors dried while on the press, while graphic items are allowed to dry between colours that are then printed with another screen and often in a different color after the product is re-aligned on the press.

Most screens are ready for recoating at this stage, but sometimes screens will have to undergo a further step in the reclaiming process called dehazing. This additional step removes haze or “ghost images” left behind in the screen once the emulsion has been removed. Ghost images tend to faintly outline the open areas of previous stencils, hence the name. They are the result of ink residue trapped in the mesh, often in the knuckles of the mesh (the points where threads cross).

While the public thinks of garments in conjunction with screenprinting, the technique is used on tens of thousands of items, including decals, clock and watch faces, balloons, and many other products. The technique has even been adapted for more advanced uses, such as laying down conductors and resistors in multi-layer circuits using thin ceramic layers as the substrate.

What can be Screen printed?

Screen printing is more versatile than traditional printing techniques. The surface does not have to be printed under pressure, unlike etching or lithography, and it does not have to be planar. Different inks can be used to work with a variety of materials, such as textiles, ceramics, wood, paper, glass, metal, and plastic. As a result, screen printing is used in many different industries, including:

Balloons
Clothing
Decals
Medical devices
Printed electronics, including circuit board printing
Product labels
Signs and displays
Snowboard graphics
Textile fabric
Thick film technology

What is a Heat Press?

A heat press is a machine engineered to imprint a design or graphic on a substrate, such as a t-shirt, with the application of heat and pressure for a preset period of time. While heat presses are often used to apply designs to fabrics, they can also be used to imprint designs on mugs, plates, jigsaw puzzles, and other products.

Both manual and automatic heat presses are widely available. A new style of press that is semi-automatic has entered the market as well, allowing for a manual closing process with an automatic opening. Digital technology in newer machines enables precise control of heat and pressure levels and timing. The most common types of heat press employ a flat platen to apply heat and pressure to the substrate. In the “clamshell” design, the upper heat element in the press opens like a clamshell, while in the “swing-away” design, the heat platen swings away from the lower platen. Another design type a “draw style press” allows for the bottom platen to be pulled out like a drawer away from the heat for preparation of the graphic. Vacuum presses utilise air pressure to provide the necessary force and can achieve high psi ratings.

Most heat presses currently on the market use an aluminum upper-heating element with a heat rod cast into the aluminum or a heating wire attached to the element. For high-volume operations involving the continuous imprinting of items, automatic shuttle transfer presses are used. The substrates to be imprinted are continuously loaded onto the lower platen and shuttled under the heat platen, which then applies the necessary heat and pressure.

The pattern is printed in sublimating ink on sublimating paper which allows the pattern to transfer. You can get some highly effective patterns and great effects using this technique.

some content from wikipedia