26/06/2007 by conrad.

The Background of Wallpaper

Wallpaper is a nonwoven (paper) or woven (fabric) backing, decoratively printed for application to walls of a residence or business. Wallpaper is not considered essential to the decoration of a structure; however, it has become a primary method by which to impart style, atmosphere, or color into a room.

The wallpaper industry divides the manufacture of wallpaper into those used in residences and those hung in businesses or other public buildings. The two categories of paper differ in weight, serviceability, and quality standards. Residential wallpapers are made from various materials and can be purchased prepasted or unpasted. There are no mandated serviceability tests for residential papers. Commercial wallpapers are divided into categories based on weight and the backing composition. Commercial wallpapers must have a vinyl surface and pass rigorous physical and visual tests as mandated by the Chemical Fabrics and Film Association.

There are five major methods used to print wallpapers, and designers choose the printing technique based on cost as well as aesthetics.

History of Wallpaper

The earliest wallpapers used in Europe as early as the thirteenth century were painted with images of popular religious icons. Within the next few centuries, wallpapers were hand block-printed, but only remained popular with the poorer classes.

In the sixteenth century, more expensive wallcoverings, depicting tapestries hung in homes of nobility, became popular with the middle classes. Small sheets either carried a repeating image, or several blocks produced a pattern spread across many sheets. Fashionable eighteenth century Americans puchased wallpapers from France and England.

Two problems plagued wallpaper stainers until the 1850’s. One was the problem of producing long sheets of paper for printing and the other was printing attractive wallpaper inexpensively. Until the 1750’s, rag-based paper was individually printed in sheets, then applied to walls. Then, wallpaper manufacturers were pasting the pieces together, ground coating them, then printing. In the late nineteenth century, the paper industry developed “endless” paper, or paper made in very long strips. By 1870, wood pulp had supplanted rag stock, resulting in a very cheap backing for wallcovering.

In the nineteenth century, printing costs were greatly reduced by abandoning labor-intensive block printing in favor of cylinder printing. Wood-block printers applied each color by hand using a separate block for each color in the pattern. Thus, each block had to be inked with the right color, pressed down on the paper, tapped to ensure a quality imprint, lifted up, and reinked as the printer moved down the paper roll—an expensive process. Wood blocks were supplanted by copper cylinders, which carried the design below the surface of the roll, each roll printing a single color. The cylinders were mounted within one machine and

the paper was mechanically fed between cylinders until the paper was completely printed—no hand printing involved. Thus, by about 1885 wood pulp paper printed with cylinders so greatly reduced wallpaper costs that it was cheaper to wallpaper a house in the United States than to paint it.More recent advances include development of additional printing methods, new inks and solvents, and use of latex and vinyl as coatings or laminates.

Raw Materials

Wallpaper consists of a backing, ground coat, applied ink, and sometimes paste on the backing used to adhere the wallpaper to the wall. Non-woven backings can be of ground wood, wood pulp, or wood pulp with synthetic material. Woven backings are those made of sturdy woven textiles such as drill (heavy woven cotton much like jean material). The woven backing is then coated and printed.

The ground coat is the background color laid on the surface, which receives the printed pattern. Coatings or laminates are made of latex or vinyl (polyvinyl chloride) and render the paper durable and strippable. Ground coats also include additives that enhance the ease of handling, opacity, and drapability of the paper.

The paper is printed with inks composed of pigment and a vehicle which ties the ink to the backing. Solvents can be acetone or water, for example. Printers choose inks carefully as the solvents they include affect the drying time and production time between color applications of the paper.

Pastes may or may not be applied to wallpapers. If they are, they are usually made up of cornstarch or wheat starch and are applied wet to the backing. Prepasted wallpapers must be rewetted for adhesion to the wall.

Design

New wallpaper designs are generally derived from sketches purchased from a staff designer or freelance wallpaper designer. The artist lays out the design on tracing paper and completes at least a partial pencil sketch. The marketing and design staff will then decide if the paper is the right “fit” for a specific look or line. If the design is accepted, the artist produces a full-scale color sketch in various colors and palettes.

After the printing process is chosen, the sketch is fine tuned to fit the requirements of the printing process and the pattern is sent to the engraver or screen-maker. Once the cylinder or screens are in place and a few pattern repeats are printed, a “strike off’ (sample wallpaper) is printed to test the color and pattern. When okayed, the paper is commercially printed in large runs.

Making the wallpaper

• 1 Ground wood sheets of paper are produced by using an entire tree, removing the bark, and pressing the tree against a revolving tread, which grinds the wood into slurry. The slurry is used to make a ground wood sheet—a relatively inexpensive wall-paper backing.

  Wood pulp sheets are made by debarking a tree and chipping the tree into a slurry. The mixture is run through a pulp mill where chlorine dioxide and oxygen are added to separate the lignin (which cements the woody cell walls together) from the rest of the wood pulp and bleaches the pulp. Wood pulp sheets with fibers can have synthetic fibers added to give the paper additional texture.

  A roll of paper from the paper mill is 65 in (1.65 m) wide, possibly as long as 22,000 ft (6,706 m), and weighs approximately one ton. Once sold to a printer, each paper roll is cut into six sub-rolls which are 21 in (53 cm) wide by 10,000 ft (3,048 m) long.

Wallpaper Coating

• 2 Before the pattern is printed, the backing must be coated with a ground color. Ground wood sheets are coated with colored vinyl (PVC), which varies in thickness depending on the durability and strippability of paper under production. Vinyl may also be laminated to backings for exceptional serviceability.

  Wood pulp sheets are coated with one or all of the following: kaolin clay for drapability, titanium dioxide for opacity, and latex for ease in handling and color.

Wallpaper Printing

There are five possible types of printing techniques.

• Surface printing. Metal rollers impregnated with a raised rubber pattern are mounted on a single machine. Ink is applied to the surface roller, and the ink lays in the hills or rubber pattern sitting above the surface of the roller. The ink is then pressed onto the paper.
• Gravure printing. Each color of the pattern is printed with a single roller. Copper cylinders are laser-etched then chrome-plated for durability. Large gravure-printing machines hold a maximum of 12 cylinders that together create the whole pattern. The paper roll moves to one cylinder, a back roller picks up color and pushes it against an engraved roller. A steel doctor blade pushes against the engraved cylinder, forcing ink into the etched detail. A rubber roller then presses paper against the cylinder, enabling it to pick up the ink in the valleys of the engraving. Finally, rollers carry the paper away from the cylinder into a dryer, where the ink is set. Once the ink is dry, the process begins again with the next cylinder.
• Silk screen printing. Stencils for each color present in the pattern are created from silk mesh screen, using a photographic
  

  Patterns can be printed onto wall-paper by one of several printing methods, including gravure printing, rotary printing, and silk-screen printing.

  process. First, a photographic negative is made of the pattern. Then, a silk screen approximately 36 in (91 cm) long is stretched taut over a magnesium or wood frame. The screen is coated with a light sensitive emulsion, and the negative is placed on top of the screen. Once hit with bright light, the emulsion hardens in the areas not covered by the negative, forming a stencil.Paper is set upon a long table, a screen stencil is placed on top, and ink is applied by a scraper or squeegee. Color is deposited on the paper where the screen permits the ink to pass through to the paper. The stencil is picked up, moved down the paper, and inked again along the entire length of the paper roll.

  Before the next color is applied, the ink is thoroughly dried. Each screen is carefully put down with blocks, guides, etc. so that the pattern is aligned and repeats without breaks. Hand printing produces patterns with thick, evenly applied color. Theoretically, the number of colors used in the screening process is limitless; however, the high cost of hand printing necessarily limits the number of colors companies can include in the pattern.

• Rotary printing. This type of printing process combines the mechanics of gravure printing with the precision of photographically produced stencils. Mesh stencils are wrapped around hollow tubes mounted within a machine. Ink continuously flows through the film-wrapped tubes and onto paper, imparting a tremendous amount of color (a maximum of 12 colors). This technique resembles the more expensive silk-screening, but it can print much more quickly—approximately 80 yd (73.12 m) of wallpaper per minute.
• Digital printing. This type of printing is the newest form of printing and probably the slowest. Intended for small runs, the advantage digital printing has over conventional printing is there are no expensive costs for separations or printing rollers.  Company Director of Concept Coverings and planbseparations Ltd believes that the future is in digital printing and engraved gravure rollers will be a thing of the past, hence wht he came out of the engraving trade to set up his companies doing digital separations and digital printing.
• http://www.conceptcoverings.co.uk/

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26/06/2007 by conrad.

Applications

Screen printing is arguably the most versatile of all printing processes. It can be used to print on a wide variety of substrates, including wallpaper, paperboard, plastics, glass, metals, fabrics, and many other materials. including wallpaper, plastics, glass, metals, nylon and cotton. Some common products from the screen printing industry include posters, labels, decals, signage, and all types of textiles and electronic circuit boards. The advantage of screenprinting over other print processes is that the press can print on substrates of any shape, thickness and size.

A significant characteristic of screen printing is that a greater thickness of the ink can be applied to the substrate than is possible with other printing techniques. This allows for some very interesting effects that are not possible using other printing methods. Because of the simplicity of the application process, a wider range of inks and dyes are available for use in screen printing than for use in any other printing process.

Utilization of screenprinting presses has begun to increase because production rates have improved. This has been a result of the development of the automated and rotary screenprinting press, improved dryers, and U.V. curable ink. The major chemicals used include screen emulsions, inks, and solvents, surfactants, caustics and oxidizers used in screen reclamation. The inks used vary dramatically in their formulations (GATF 1992b).

Screen Printing Process Overview

Screen printing consists of three elements: the screen which is the image carrier; the squeegee; and ink. The screen printing process uses a porous mesh stretched tightly over a frame made of wood or metal. Proper tension is essential to accurate color registration. The mesh is made of porous fabric or stainless steel mesh. A stencil is produced on the screen either manually or photochemically. The stencil defines the image to be printed in other printing technologies this would be referred to as the image plate.

Screen printing ink is applied to the wallpaper substrate by placing the screen over the material. Ink with a paint-like consistency is placed onto the top of the screen. Ink is then forced through the fine mesh openings using a squeegee that is drawn across the scree, applying pressure thereby forcing the ink through the open areas of the screen. Ink will pass through only in areas where no stencil is applied, thus forming an image on the printing wallpaper substrate. The diameter of the threads and the thread count of the mesh will determine how much ink is deposited onto the substrates.

Many factors such as composition, size and form, angle, pressure, and speed of the blade (squeegee) determine the quality of the impression made by the squeegee. At one time most blades were made from rubber which, however, is prone to wear and edge nicks and has a tendency to warp and distort. While blades continue to be made from rubbers such as neoprene, most are now made from polyurethane which can produce as many as 25,000 impressions without significant degradation of the image.

If the item was printed on a manual or automatic screen press the printed product will be placed on a conveyor belt which carries the item into the drying oven or through the UV curing system. Rotary screen presses feed the material through the drying or curing system automatically. Air drying of certain inks, though rare in the industry, is still sometimes utilized.

The rate of screen printing production was once dictated by the drying rate of the screen print inks. Do to improvements and innovations the production rate has greatly increased. Some specific innovations which affected the production rate and has also increased screen press popularity include:.

1. Development of automatic presses versus hand operated presses which have comparatively slow production times.
2. Improved drying systems which significantly improves production rate.
3. Development and improvement of U.V. curable ink technologies
4. Development of the rotary screen press which allows continuous operation of the press. This is one of the more recent technology developments.

Screen Preparation

Screen (or image transfer) preparation includes a number of steps. First the customer provides the screen printer with objects, photographs, text, ideas, or concepts of what they wish to have printed. The printer must then transfer a “picture” of the artwork (also called “copy”) to be printed into an “image” (a picture on film) which can then be processed and eventually used to prepare the screen stencil.

Once the artwork is transferred to a positive image that will be chemically processed onto the screen fabric (applying the emulsion or stencil) and eventually mounted onto a screen frame that is then attached to the printing press and production begins.

Screen Printing Presses

There are three types of screen printing presses. The flat-bed (probably the most widely used), cylinder, and rotary.

Until relatively recently all screen printing presses were manually operated. Now, however, most commercial and industrial screen printing is done on single and multicolor automated presses.

Screen Reclamation (post-press)

Why reclaim screens?

Polyester fabric costs $10-40 per square yard.

Failure to reclaim screens and ruined screens cost on average $5,000-$10,000 per year. The average monthly fabric cost $360. One study showed chemical reclamation cost between 2 and 10 dollars per average screen, while screen disposal cost just shy of 50 dollars.

The process of reclaiming screens generates solvent waste and waste water. Solvent waste generated from screen cleaning and waste water is generated through the process of emulsion removal. The waste water will contain particulates comprised of ink pigment, emulsion and emulsion remover (periodate).

Screen Printing Inks

Screen printing inks are moderately viscous inks which exhibit different properties when compared to other printing inks such as offset, gravure and flexographic inks though they have similar basic compositions (pigments, solvent carrier, toners, and emulsifiers). There are five different types of screen ink to include solvent, water, and solvent plastisol, water plastisol, and UV curable.

For Rotary Screen Engraver visit Meshtex UK

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26/06/2007 by conrad.

A big thank you goes out to all the separation artists who have worked with us over the last 12 months.

This is not only our digitally printed wallpaper  artists but our spot colour separation artists for wallpaper too.
Coming in the next week……………..

How separations are done and what is the difference between separations for digital printing and separations for wallpaper and textiles

We uncover the myth of wallpaper separations and show an in depth demonstartion from start to finish.

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26/06/2007 by conrad.

We have today entered into a competition at www.the100lists.com/seoblog/ for website of the month competition.  Once the wallpaper featured listing has been received, hopefully, we may be able to win the competition.

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23/06/2007 by conrad.

Wallpaper has been around for hundreds of years, and yet people claim that there has been very little advancement in wallpaper. At the surface it might seem like a remark that seems true, but the truth is far from it, wallpaper has evolved from the really old looking red and white stripe paper, to a work of art that can adorn your home, or your work place. There are more or less no limits to the colours, variations and styles you can choose from, the best part is, contrary to popular belief wallpaper has evolved and changed as time has gone by, and they are no longer just another thing you put on your walls.

Just like art and fashion has evolved, so have the various styles of wallpaper, earlier wallpaper was made to resemble the various tapestry styles, as fashion style and taste of people evolved, the wall papers became more and more diverse. Just like clothing, technology and so many other things today, wallpaper has now come to reflect the taste and moods of a home owner. With the numerous advances in technology, the method of printing wallpaper too has advanced, earlier massive offset printers, or block printers were used to manufacture wallpaper, where as today more and more people are turning to digitally printed wallpaper for their homes.

Today wallpaper is classified based on the commercial application, and is divided into two categories commercial and home use wallpaper

Commercial Wallpaper

Commercial wallpaper is usually printed on thicker, and more resistant paper. Since commercial wallpaper (as the name suggests) is used in retail outlets, hotels, discos etc. The wallpaper has certain health and safety specifications that it must meet like being fire resistant etc. Apart from the health and safety requirements, there are additional requirements like being easy to clean, dust and dirt resistant etc. What has made commercial wallpaper making an entirely different section, is that more often than not commercial wallpaper involves customization like having a company logo printed or having custom designs, this is where having a digitally printed wallpaper comes in handy, as the imagery that is produced using digitally printed wallpaper is far superior when compared to wallpaper printed using traditional methods.

Wallpaper for home use

The earliest and oldest application of wallpaper is for home use, wallpaper for home use is by no way inferior to commercial wallpaper, as it too has to meet strict quality control guidelines, however the added advantage that wallpaper for home use has is that, it is easier to apply when compared to commercial wallpaper, and in addition you can have multiple wallpaper in the same home (compare this to commercial establishments where the wallpaper is uniform throughout). Just like commercial wallpaper, digitally printed wallpaper is available for home users also, the biggest benefactors of digitally printed wall paper have been home owners, who can now either get custom wallpaper with a particular design built, or can choose to adorn their home walls with some of the greatest works of art ever made. The choices that wallpaper today has bought to home owners is just mind boggling, and all it takes to get customized wallpaper made is a photograph or image of your design.

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19/06/2007 by conrad.

Wallpaper sets the mood with the color and design. A bright, cheerful wallpaper lightens up the room, while a dark and dramatic wallpaper immediately sets a formal, more elegant feeling to the room. Wallpaper can also change the look and feel of a room’s size / dimension, making it feel bigger, smaller, taller, or more cozy. With wallpaper, you can create anything you want, the only limitation being your imaginataion. Because wall papers are available in so many colors, textures, patterns and styles and are so easy to install, they have a place in every room in the house. Go ahead, buy a new wallpaper today and change the feel of your home.

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08/06/2007 by conrad.

We have just printed 6 rolls of bespoke wallpaper for The Gaurdian Newspaper.  The wallpaper will feature at Glastonbury festival at the entrance to The Gaurdian tent.

The order was placed 6/6/07 and all 6 rolls of wallpaper were shipped to the client 8/6/07.

Due to copyright reasons we are not showing the wallpaper.  Maybe after the event, Russel Turk from The Gaurdian will send us some pictures.

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02/06/2007 by conrad.

Our new studio has been completed in the last couple of weeks.  It comprises of a state of the art technical wallpaper studio, where wallpaper is separated and printed, all in house.

We believe our newly furbished studio is the best in the area at what it does.  Over the years I have worked and managed many wallpaper stuios, Crown Wallcoverings was one of them, but this studio is the best I have ever worked in.

The atmosphere is relaxed and easy and the days go  very quickly, especially when you are doing something you love, colour separating and printing wallpaper.

If anyone wants pictures please post comments and I will upload some.

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