History
17th Century
While the exact origins of wallpaper are obscure, the first known decorative wallpaper dates back as far as the late 15th century, soon after the introduction of papermaking in Europe. Although it is generally believed that the Chinese invented wallpaper, there is no evidence of its general use in Asia any earlier than the time of its appearance in Europe. The earliest wallpapers were hand-painted or stencilled. Later, during the 17th century, decorative techniques such as block printing and flocking were adopted. At the end of the 17th century, Chinese papers, generally referred to as India papers, began to arrive in Europe. These highly prized papers were unique in design and Europeans quickly attempted to copy the designs using etched plates or woodblocks, with colour applied by hand or stencil.
18th Century
During the 18th century, wallpaper manufacturing became much more sophisticated and designers began to explore many more decorative possibilities. In France and England, chintz patterns, satin grounds and stripes became popular and technical advances began to make wallpaper more widely accessible. In 1785, Christophe-Philippe Oberkampf invented the first machine for printing wallpaper. Shortly thereafter, Louis Robert designed a process for manufacturing endless rolls.
While the French were famous for their fine designs, the English were known for advances in the production techniques, especially in the mid-19th century with advances in machine-printed wallpaper. In the 1840s to 1860s, the work of William Morris and the Arts and Crafts Movement created a revolution in wallpaper design, characterized by flat, stylized, naturalistic patterns and rich, subdued colours.
After WWII
Few important advances occurred during the next 100 years. The 1950s and '60s brought significant developments in wallpaper design and manufacture. New processes enabling designers to decorate wallpaper with photogravure and high-speed techniques were developed to replace the more traditional screen-printing and woodblock methods.
Finally, after World War II, the entire industry was revolutionized with the appearance of plastic resins - especially vinyl - which offered stain resistance, washability, durability and strength. In addition, manufacturers introduced pre-pasted, pre-trimmed and strippable wallcoverings to cater to an increasing do-it-yourself market.
Common Terms
The following terms are commonly used to describe important characteristics of wallcoverings:
- Washable means that a wallcovering can withstand occasional sponging with a prescribed detergent solution.
- Scrubbable means that a wallcovering can withstand scrubbing with a brush and a prescribed detergent solution. (No abrasive cleanser should be used.)
- Stain resistance is the ability to show no appreciable change following removal of different types of stains such as grease, butter, coffee, etc., after a set period of time.
- Abrasion resistance is the ability to withstand mechanical actions such as rubbing, scraping or scrubbing.
- Colourfastness is the ability to resist change or loss of colour caused by exposure to light over a measured period of time.
- Peelable means that the decorative surface and ground may be dry peeled leaving a continuous layer of the substrate on the wall which can be used as a liner for hanging new wallcovering. Peelable wallcoverings today are usually paper-backed vinyl products in which a paper substrate is coated with a vinyl plastisol.
- Strippable means that the wallcovering - complete with the substrate - may be dry peeled. Fabric-backed vinyl wallcoverings are usually strippable.
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Product Characteristics
Most wallcoverings have the following three layers, each of which performs an important function:
- The decorative layer, which is the top layer, is comprised of inks and a protective polymer coating applied to the top of the intermediate layer. Normally the thinnest layer, the decorative layer is usually the major reason a wallcovering is chosen. The design and/or texture is printed using various methods such as gravure, flexography, surface printing and screen-printing.
- The intermediate layer, or the ground, provides the surface upon which the decorative layer is printed. It also provides the background colour which, while often an off-white, can be any colour depending upon the design. This layer can range in thickness from less than one mil to as much as 30 mils in heavier-weight, "solid-vinyl" products. (Note: A mil is 1/1000 of an inch.)
- The substrate or backing is the portion of the wallcovering that goes against the wall. This backing can be of a wide variety of materials ranging from woven and nonwoven fabrics to lightweight paper products. Substrates are used in the manufacture of vinyl wallcoverings because vinyl itself is not peelable if placed directly on a wall.
The combinations or constructions of these various layers and materials provide the characteristics typical in wallcoverings such as degrees of strength or durability, scrubbability, washability, stain resistance, abrasion resistance, colourfastness, etc.
Heavy-duty vinyl wallcoverings are recommended wherever walls are subjected to severe abuse, such as high-traffic areas in healthcare, institutional, corporate, retail and hospitality interiors. Vinyl protects walls, wears longer than paint and is less expensive to maintain. In very demanding areas, rigid vinyl sheet provides the most durable protection without compromising aesthetic benefits. Even tough commercial product lines are available in appealing and varied designs, including warm colour palettes and floral patterns that combine beauty with heavy-duty performance. Vinyl wallguards, chair rails, corner guards and kick plates complete the protective wall system.
Types of Vinyl Wallcovering
There are several categories of vinyl wallcovering, each with specific performance characteristics:
Vinyl Coated Paper (VCP)
A paper substrate coated with acrylic. Although more resistant to grease and moisture than plain paper and suitable for residential kitchens and bathrooms, it does not resist excessive and prolonged exposure to grease, moisture or abuse. Thus, it is not suited for commercial applications.
Paper Backed Vinyl/Solid Sheet Vinyl (PBV)
A paper substrate coated with a vinyl plastisol. This sheet is thicker than the plastisol coating and provides greater durability. This type is classified as scrubbable and peelable, and can be used in most areas of a residence or business since it resists moisture, stains and grease. It will not withstand hard physical abuse, however.
Fabric Backed Vinyl (FBV)
A solid vinyl intermediate layer laminated to a woven or nonwoven fabric substrate. The vinyl layer can vary from two to 35 mils in thickness. The thickness of the woven fabric is about 10 mils and that of the nonwoven fabric is about six mils. Fabric-backed vinyls usually are strippable and unpasted, and provide a vapour barrier that will keep cold air in and warm air out. Three types are available to meet different situations:
- Type I: For less heavily travelled areas subject to minimal scuffing and abrasion, such as above chair rails in hotel guest rooms and office buildings.
- Type II: For general use in areas where traffic and scuffing are major issues, such as foyers, lounges, corridors and classrooms.
- Type III: Primarily used as wainscot or lower protection for areas exposed to heavy traffic by movable equipment or rough abrasion, such as hospital corridors, storage and utility rooms, food service areas and elevator foyers.
Rigid vinyl sheet
A solid sheet wallcovering developed for use in commercial areas where the potential for high-impact damage is of concern. This product does not usually have a backing and is installed with special contact adhesive.
Mould and Mildew Problems
Manufacturers of vinyl wallcoverings have taken steps to address mould and mildew problems. The primary cause of mildew is condensation caused by warm, humid air infiltrating the wall cavity. Because vinyl wallcoverings are fairly impermeable, they act as something of a vapour barrier trapping moisture inside the wall cavity, where it condenses against the relatively cool inside surface of the wall. This is called "concealed condensation." Prolonged exposure to these conditions will result in deterioration of the gypsum board, allowing the growth of mildew. A permeable membrane, such as Tyvec®, on the outside wall part of the wall cavity helps vent moisture.
It is important to eliminate the moisture at its source, with proper window installation, caulking and sealing, for example. Proper wall preparation is also important, as starch-based wallcovering adhesives can serve as a food source for microorganisms that may be present on damp surfaces. In areas of concern, wallcovering systems that include adhesives and primers formulated to inhibit the growth of mildew should be specified.
Even wallcoverings that are labelled "mildew resistant" can trap condensation. Some manufacturers have introduced "microvented" wallcoverings that allow moisture to escape. If water infiltration problems exist within the building, "breathable" wallcoverings should be selected to avoid mildew problems.
Technical Data
Residential wallcoverings vary in width and length and may be priced by the single roll, but are generally packaged in double or triple rolls.
Commercial wallcoverings are commonly sold by the lineal yard and come in varying widths.
Installation
One of the most critical parts of wallcovering installation is proper preparation of the wall surface to insure that the wallcovering will adhere properly. The surface must be clean, dry, structurally sound and free of grease, mildew or other stains. Gloss and semigloss paint must be sanded to dull the surface and a coat of adhesion-promoting primer applied prior to wallcovering installation. Any wall irregularities should be repaired, then the wall surface primed and sealed. Stains or mildew must be removed to prevent bleeding through the wallcovering.
Surface treatment will vary according to type. New drywall, new plaster and painted surfaces must be primed. Liner paper may be required on masonry and panelled walls. Walls from which old wallcovering has been removed must be sanded or cleaned with an adhesive remover to prevent the development of mould and mildew.
Another critical issue involves the choice of adhesives, which are formulated for specific applications and vary in level of wet-tack, strippability and ease of application. Heavyweight vinyl wallcoverings require specifically formulated adhesive. See the manufacturer's instructions to select the proper adhesive for the application.
Maintenance Requirements
Vinyl wallcoverings are more resistant to scratching and tearing than alternate coverings. Typically, vinyl wallcoverings last three to five times longer than other surface treatments, such as paint.
Low-cost maintenance consists of cleaning with mild detergent to remove accumulated dirt, grease and most stains without damage. Virtually invisible repairs can be made to severely damaged areas by using surplus material.
Always refer to the manufacturer's guidelines when cleaning wallcoverings. Stains should be removed as soon as possible to eliminate any possible reaction between the stain and the wallcovering. If soil remains on the wallcovering too long, permanent discoloration may result. Ordinary dirt spots can be removed with a mild soap and warm water. Rinse thoroughly with clean water. Blot wallcovering dry with a soft, lint-free towel. For more difficult stains that are only surface deep, a stronger detergent is recommended. Try an inconspicuous spot first before attempting the entire wall. One should always rinse after applying a detergent. Abrasive rubbing of spots should be avoided. Use of steel wool, powdered cleaners or active solvent-type preparations, such as nail polish remover, tar and bug removers, etc., may damage the wallcovering.
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Selection and Specification Guide
ASTM has defined standard classifications of wallcoverings by durability characteristics. There are six types described by this specification, defining minimum standards for such performance issues as colourfastness, washability, scrubbability, abrasion resistance, tensile strength, crocking resistance and tear resistance.
Several independent third-party testing labs have established labelling programs for wallcoverings that serve as a control program. These measure characteristics of the construction such as vinyl weight, fabric weight, adhesive application weight, coating adhesion and tensile strength of the product. In addition, independent laboratories have established file descriptions on the fire test performance of a product, which includes certain physical tests, a description of the vinyl formulation and the fabric backing, and an appropriate classification as to flame spread and smoke developed.
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Raw Materials
All vinyl products are made from a unique combination of vinyl resin and various additives that give these products their particular properties. For more information on the vinyl resin process, see general vinyl section. Every formulation is different, and most are proprietary. Some of the additives commonly used in vinyl wallcovering include:
- Plasticizers, which give the finished product such properties as flexibility at low temperatures, fire retardance, resistance to staining and abrasion and long-term aging. Since plasticizers tend to counteract each other, it's impossible to formulate a vinyl product with the ultimate in all properties. The balance is shifted within product lines to produce wallcoverings that emphasize certain characteristics.
- Stabilizers, which prevent the vinyl compound from degrading during high temperature processing and help protect the finished product from discolouring during its useful service life.
- Other additives, such as pigments, mildewcides, fungicides, flame retardants or smoke suppressors. Low levels of biocides are used in the vinyl compounds to inhibit the growth of various microorganisms on the product itself.
Processing / Fabricating
Once the additives have been combined with the resin, the resulting material is called a vinyl compound and can be in pellet or powder form. The nature of the vinyl compound allows versatility in the production process, enabling manufacturers to meet a host of performance requirements. The next stage of vinyl wallcovering manufacturing generally consists of the following steps, which take place at relatively high speeds under carefully controlled conditions.
Mixing
Resins, plasticizers, stabilizers, pigments, biocides, fire retardants and other ingredients are carefully weighed and blended. This batch of ingredients is mixed to create a uniform melt of the ingredients. Multiple batches are then blended and milled for uniform feed of the compound melt to the calender train. Prior to actual calendering, the batches are put through a strainer-tuber that removes any impurities from the finished product. The product then moves onto the calender, where large, temperature-controlled rolls form the compound into a thin film. Either prior to or after laminating, the vinyl sheet can be decorated using any of the previously described printing techniques.
Colouring and Printing
If the final product is to be a plain, solid colour material requiring no surface printing, ink-wiping or other finishing techniques, the material is "in-line-embossed" at this point, then packaged.
To create the illusion of dimension, the embossed, fabric-laminated sheet is passed through a series of inked rollers to add a colour to contrast with the base film colour in a process called "Spanishing" or "shadow printing." The process leaves most of the ink in the valleys of the embossed surface and removes most of it from the raised portions, creating a three-dimensional textured effect. In the printing process, a distinct pattern design is created by the use of inks applied by one or more etched print rollers. Finally, a top coat can be applied to the vinyl surface by etched rollers to add the desired sheen to certain patterns. Print inks may impart a gloss, a semigloss or a matte finish to the product. One of the decorative advantages of vinyl wallcovering is its ability to hold texture when it is embossed, whereas embossing is not permanent on a paper surface.
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