Wallpaper: A Paper Primer

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Wallpaper: A Paper Primer

Why the installation of paper must be different from vinyl -- a book excerpt

This article is adapted from a chapter in The Showroom Handbook for Wallpaper Installations by Certified Paperhanger Bob Kelly. As he writes in the preface, "The simple truth is that there are dramatic differences between most wallcoverings sold at retail and those wallpapers found in showrooms." However, with enough information and planning, Kelly writes, every showroom-quality wallpaper installation can be brought to a successful conclusion.

Defining wallpaper: The world of wallcoverings is a world of variety. There are probably as many as 100 different types, printed on dozens of different substrates. This handbook discusses only showroom-quality blockprints, domestic handprints, and imported machine prints. For the purposes of this book, these three will be defined as "wallpaper" to differentiate them from all other types.

Many wallcoverings sold at retail could also be classified as wallpaper, because their substrates are paper-based. And there are many wallcoverings sold in showrooms that could be classified as vinyls; screen printed paperbacked vinyls, for example. However, this article seeks to draw a basic distinction between the paper types (which are most often found in showrooms) and the vinyl types (which are most often found at retail).

Most traditional papers have certain qualities that set them apart from vinyls and vinyl-coated papers. Traditional papers:

1. Are usually highly porous on the back side
2. Are usually breathable on the front side
3. Often undergo a color change when pasted
4. Are often delicate, compared to vinyl types
5. Are usually unpasted

Definition: The term "wallpapers" describes the finer-quality unpasted papers which are porous on the back side and relatively breathable on the front side.

Paper vs. vinyl: Many of today's installers, trained on vinyls or vinyl-coated paper, are unfamiliar with the requirements of traditional wallpaper. This is true whether the product is a traditional European paper or a top-of-the-market domestic handprint. Vinyl types are made to be durable; they are washable, and may even be scrubable. Most of the paper types, on the other hand, are delicate -- they need a soft touch during installation.

Of the three types discussed in this book, domestic handprints are the least "paperish," because they are usually printed on a strippable substrate. This type of substrate is composed of paper, which has been strengthened by the addition of resin binder. The inks used also make them less breathable than the other two types.

The more a paper is coated with ink, the less it "breathes" (allows moisture and air to escape through the surface of the wallpaper). A very heavily coated paper tends to behave like a vinyl. Wallpapers will eventually wet out (become fully expanded), while vinyl types generally have no need to relax as fully.

Wallpapers accept a lot of moisture during the pasting process. They expand, always across the grain (width), and contract somewhat as they dry. Because they breathe, they allow moisture and air to escape; whereas vinyl types are likely to trap both moisture and air.

Wallpapers, at the microscopic level, are made up of bundles of fibers that have enough integrity to stay together, but enough "looseness" to become flexible when pasted. During the pasting, hanging, and contraction process a great deal of stress is put on the paper, which in turn puts a great deal of stress on the wall. Papers readily accept a thin, starchy paste and are easily adhered to the wall.

All of these traditional paper types are, to a greater or lesser degree, water-sensitive. This means that although they need to be hung with a high-moisture paste, they need only a certain amount. They can be damaged by excessive amounts of paste, the wrong type of paste, or incorrect hanging techniques.

The installation cycle: Paper types: Let's look at what happens when a wallpaper is pasted. First, a high-moisture paste is applied to the back of the paper. Almost immediately the paper begins to buckle, as the fibers of the paper expand at different rates. After five minutes, most papers are fully expanded, and the width of the sheet begins to equalize. If the paper stock is thick and porous, double-pasting may be necessary to fully coat the back of the paper. The paper may tear easily, and booking the sheet must be done carefully.

Meanwhile, changes occur to the front of the paper. A darkening "blush" may appear, as the moisture begins to affect the inks. Depending on the amount of penetration, this may spread into a full-blown color change throughout the sheet. The paper when fully expanded is limp, relaxed, and cool to the touch.

During installation, the paper is flexible -- it can be pushed or pulled as necessary to make a butt seam to a neighboring strip. Once the strip is swept down against the wall with a soft bristle brush, the paper immediately begins to lose moisture. Not only does moisture from the paste begin to sink into the wall, but it also begins to evaporate through the face of the paper into the air. The sheet begins to look blotchy, as the colors dry and lighten.

Ideally, within 10 or 15 minutes, the sheet is ready for seam rolling with a wooden seam roller. This will set the seam and the installation is complete. There is usually a slight contraction of the seam during drying.

So how does this differ from the vinyl types?

Vinyl types: First, a minimal amount of a high-tack, low-moisture, pre-mixed vinyl adhesive is rolled onto the back of the sheet. Ordinarily, neither buckling nor color changes take place, although some slight expansion may occur. The sheet can be brought to the wall quickly, or it can often be dry-hung (the wall is pasted and the vinyl installed directly on the wall.) The product does not tear easily, and booking is done quickly.

Solid vinyls are most often pressed into place with a short synthetic bristle brush, or a solid vinyl sweep (rigid plastic). No air is allowed to remain between the wallcovering and the wall after installation, because it might remain as a blister under the vinyl film.

The vinyl can be moved slightly during installation, but it may not stay in place because it has a "memory" -- it returns to its former shape. The vinyl is not limp, relaxed, or cool to the touch. Only by using a heat gun can vinyl be made as flexible as paper. (The extreme heat imitates the manner in which it was formed into a sheet.)

Vinyl types are ordinarily rolled vigorously with rigid seam rollers; hard plastic and steel are the norms. The sheets will not dry out, even under the best of conditions, for about 12 hours. This explains the necessity for a high-tack, low-moisture paste that will hold the vinyl in place with wet tack. There is only very slight contraction during drying.

Conclusions: What conclusions can we draw from the differing installation cycles of paper types and vinyl types?  The above descriptions should make clear that paper does not act like vinyl, before, during, or after installation. Let's look at three areas: pasting, installation, and expansion and contraction.

Pasting: Wallpaper needs water in order to relax. Suppleness is necessary not only to make a good seam, but also to follow the contours of the wall. But while paper needs water, it needs only a certain amount. Many showroom wallpapers are colored with sensitive inks that can be damaged by over-soaking the sheet or over-working the seams.

The paper should be evenly but lightly pasted, just enough to relax it thoroughly. The type, amount, and thickness of paste may need to be adjusted for the paper at hand.

Installation: Because it is much more porous and breathable, paper types do not require the same degree of pressure during installation as vinyl types. If the paste is the correct consistency, and if the face of the paper is still breathable, excess paste will dry out naturally and small expansion bubbles will tighten to the wall. They do not have to be forced out.

While vinyl types can remain moist for extended periods of time without damage, the same cannot be said for paper types. The drying cycle for paper should be as short as possible. The installer's goal is to use correct wall prep, so that the paper dries out quickly and uneventfully.

Expansion and contraction: Wallpaper expands when wet and fully relaxed, typically 1 percent. This means that a 20.5-inch paper will expand to 20 and seven-eighths inches, and that a 27-inch paper will expand to 27.5 inches. This is perfectly normal, as is the slight contraction that takes place as it dries. Vinyl types do not expand to this extent, nor do they contract as much as the paper types.

The challenge of installing wallpaper is to anticipate the amount of contraction that will take place, and plan for it with correct wall prep and technique. The use of blankstock liner provides an optimum hanging surface. An ideal surface is one that absorbs moisture quickly enough to allow the seams to be set before they have a chance to contract. If left unchecked, the contraction can result in a split seam.

In many "problem" installations, the wallpaper has arrived on the job with missing, outdated, or contradictory guidelines. In the absence of guidelines, the paperhanger may resort to hanging a paper type with vinyl-type techniques, as outlined above. When confronted with a problem installation in progress, the first question should be whether the installation techniques are properly matched to the type of wallcovering at hand.

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