Standard Operating Procedures: Paperhanging in Historic Homes
Jumat, 13 Juli 2012
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Yet tools, materials, and wall surfaces have changed. The housing market of today may be overpopulated with “cardboard boxes,” but it’s a fact that many homes built after 1920 or so have drywall, and that some of them have been deemed “historic.” Premixed adhesives are now standard and acrylic primers have replaced glue size. The adoption of pasting machines and handheld lasers have quickened the pace.
I’ve written a bibliographic essay about historic paperhanging techniques. It gives context for how paperhanging styles have changed, and lists some texts for further study. Styles matter a great deal in paperhanging. An installation of a reproduction wallpaper in a historic home should reflect the styles and handiwork and trade conventions of the time in which it was originally hung, not our own.
The aim of this article is more practical. It seeks to strike a balance between the old and new, and to answer three questions which are not related to style:
1. Given that many rooms in historic homes are prepared and papered each year, how should this be done?
2. How does this differ from other professional paperhanging work?
3. How can managers and curators of historic homes understand and facilitate such work?
What follows is a guide to the standard operating procedures. Some papers, styles, conditions or wall spaces will pose challenges not answered here. Sometimes there is no authoritative answer, even after exhaustive research. The aim is simply to spell out some of the tested techniques and accepted approaches to this interesting and important work.
a. Hiring A Paperhanger
b. Stripping
c. Wall Prep
d. Lining Paper
e. Trimming
f. Pasting
g. Hanging
h. Other Concerns
a. Hiring A Paperhanger
It may be helpful to find a Painting and Decorating Contractors of America (PDCA) member, or one who belongs to the National Guild of Professional Paperhangers (NGPP). The PDCA is a trade organization to which companies belong, the NGPP is a professional organization. However, the standards for belonging to these groups don’t guarantee that members have advanced or specialized skills. Another drawback is that both groups are relatively small.
There are different tribes of paperhangers and they range from traveling motel and convention center crews to union members in large cities to high end decorating specialists to residential hangers in towns and rural outposts. Ask around. An emerging phenomenon is that more women have joined the ranks. Some years ago it was determined that the NGPP membership was about 30% female.
After a short list is compiled, take time to interview candidates, show them the proposed work, and ask for input. Topics should include the scope of work, how the work should be done, and with what materials. Collaborations can work, even at the pre-bidding level, because many paperhangers are problem solvers and respond well to challenges. From these discussions a realistic set of specifications can be hashed out and bids can follow.
Specifications developed in this way are likely to match the requirements of the job. At the other extreme is a reliance on specifications from authorities in the field or from manufacturer’s recommendations. These are interpreted and administered by some or all of the following: Architects/General Contractors/ Designers/Subcontractors/Sub-subcontractors, and Project Managers.
There are three problems with this approach: 1. there are very few authorities in the field; 2. boilerplate imposed from afar rarely fits the work at hand (this seems to be particularly true in historic houses); and 3. bidding packages based largely on price and minimum standards are usually won by contractors, not craftspeople.
Because of this last point, the completed project may fit the letter of the law of bidding documents and manufacturer recommendations, yet still fall short of a quality standard.
b. Stripping
To a large extent, stripping depends on how the previous wallcoverings were installed. Some papers are delightfully easy to strip and need only a tug at a corner. Most are more securely fastened.
If the paper can’t be dry-stripped easily, testing is in order. An efficient method needs to be worked out. Dry removal (mechanical) is preferable because the alternative (wet stripping) can cause fugitive evidence, like traces of waterbased paint and pencil marks, to be washed away. If excessive amounts of water are used during soaking, the runoff might get into cracks and affect lower floors.
Often, a wallpaper’s surface is porous. This can be checked by soaking a small area with a sponge. If the wallpaper changes color, it’s porous. If it’s not porous, it usually takes more than soaking to remove it. In some cases, the top layer is a vinyl laminate which will strip cleanly, leaving a layer which must be saturated. If the top resists moisture (if water beads up and there is no color change) it may be necessary to break the ink film with sandpaper, followed by soaking. A surfactant can be added to the water to help it penetrate. Many liquid concentrates are commercially available.
For soaking of all types the watchword is patience. For long soaks, a commercial surfactant mixed with methyl cellulose paste can be effective. Covering this mixture with plastic prevents it from drying out. In extreme situations, steam machines and handheld abrasive devices may be used — but with caution; wall damage may result. Removing paste residue and washing the walls is always a good idea.
Dry-stripping on plaster commences by slicing into the sidewall with a 4" razor tool against the substrate. Dry-stripping on drywall calls for more caution because the cardboard surface is prone to delaminate. If the plaster or drywall is primed, the danger of damage to the wall is lessened, because primers tend to hold out moisture and protect walls better than unprimed walls. While stripping primed walls, remember to watch out for clues to earlier work. Traces of previous wallpaper patterns or decorative paint schemes, old window and door placements, shadow lines where long-missing architectural elements once rested and even significant nail and screw holes — all of these have come to light after the stripping of a papered wall.
c. Wall Prep
If repairs are needed, it’s best to match like to like: plaster repairs for plaster, joint compound for sheetrock. It’s alarming how often joint compound and related soft fillers are confused with plaster and spackle — even in historic homes. Almost all fillers are white in the dry state, but the resemblance stops there.
The older fillers are often denser and stronger. Present-day soft fillers need to be sealed and primed so that they’re ready to receive wallpaper. This is because wallpapers contract as they dry, and may rupture fillers and paint films if the underlying bonds are not adequate. Before application of primer or size, the walls should be bladed smooth with broadknives, sandpapered where necessary, and all grit removed. #80 is a good all-around grit for this purpose.
Recently, masonry-type acrylics (consolidants) have been introduced to the paperhanging field and are effective for many types of paper consolidation; for example, when top layers of sheetrock have delaminated. With some caution, they can also be used to seal so-called builder’s flat (poorly bound paint). However, alkyd primers are still the standard for consolidating flaky, sandy or gritty walls, and for isolating them from successive layers of pasted liner and finish paper. Alkyd is superior to acrylic because the resulting isolating coat is thicker, sands easier, and is more resistant to moisture.
If an alkyd primer is used, a further step is required. This is largely due to VOC regulations, which have resulted in new alkyd formulations. It’s best to cover the alkyd primer with an acrylic wallcovering primer to ensure adhesion promotion for the liner to follow.
If the plaster is raw, it should be made ready for wallpaper. Raw plaster is porous and readily drinks up adhesive, which can sabotage the adhesive bond. Plaster needs to be conditioned so that an “adhesive sandwich” is created between wall and liner. Traditionally, this was done with glue size, which was mixed to the appropriate strength.
However, glue sizes have disappeared from hardware shelves. In their places sit a variety of acrylic wallcovering primers. These seal the wall to a greater or lesser degree and yet promote adhesion. They’re different than paint primers, so it’s important to read the labels.
Some are translucent, but many are white and attempt a universal solution. They seek to combine the virtues of opacity, wall-sealing, adhesion promotion, and strippability. Whether these claims can be met for any particular combination of wall surface, adhesive and wallcovering is a good question. It’s a question that is best answered after an evaluation by a professional paperhanger. In any case, if there are concerns about covering up valuable evidence, translucent wallcovering primers are preferable to white ones.
An alternate (if somewhat weird) method for sizing raw plaster is to locate a glue size, available at art supply stores. Artists still use this product to size canvas. Granulated rabbit skin or hide glue is put into a double-boiler in an approximately 1/25 ratio with water and heated. It is then applied with brushes to the wall. Advantages: historically accurate, hides no evidence, completely reversible. Disadvantage: weird.
Woodwork should be protected from dust and paint with low-tack tape and thin plastic sheeting as needed. The floors should be protected with heavy canvas dropcloths or similar. Ladders or scaffolding must not come into contact with woodwork.
All interfaces where woodwork joins walls (the gaps) are usually caulked. Caulking should not be so full as to call attention to itself, nor so lean as to cause unsightly cavities. While caulk cannot always be color matched, a variety of colors are available at most full-service retail outlets.
d. Lining Paper
Lining paper is not well understood. It’s true that a wallpaper can be hung directly on a wide variety of surfaces. However, paper clings to another paper better than it will to anything else. Lining paper serves similar functions as a liner for drapes, or the familiar underlayment (the pad) that goes under most carpets. Just as the underlayment gives the carpet a buffer so that the carpet wears better and looks nicer for a longer time, lining paper helps wallpaper by buffering the effects of humidity and moisture. These pass through walls, especially outside walls, to a greater or lesser degree.
It also helps in the other direction. Ambient humidity, sunlight, blowing air, and even air conditioning can have an effect on the surface of the wallpaper, which contracts and expands slightly because of seasonal or shorter term climate changes. Liner restricts this movement.
Liner also helps during installation because it gives the paperhanger more control over how seams are managed, how quickly they can be rolled, and how the strips dry out. It should be clear from this line of reasoning that a liner should be porous. Again, as in the case of a wall, the porosity needs to be tempered. This is usually done with a paste size, not an acrylic or alkyd primer. These would seal the liner, and rob it of all porosity.
There are two principal types of liner (blankstock and acidfree), but before describing them we should mention two other types: bridging liners and eastern-style papers. Bridging liners are commonly sold at hardware stores and home furnishing centers. Often composed of at least 50% nonwoven or polyester, they can be recognized by their spun fibers and pure white color. They’re not suitable under reproduction wallpaper for several reasons:
1. they resist moisture and don’t provide the necessary porosity for the wallpaper.
2. their spun texture is not smooth enough to allow for setting seams properly.
For these reasons, bridging liner is best reserved for major wall repairs, and for bridging cinderblock walls, thin paneling, and the like.
The objection to eastern-style papers is quite different. These thin papers are very strong and include such types as kozo, okawara, and so-called rice papers, most of which are made of dense plant fibers. These are often used by paper conservators and are excellent papers in general, and yet are not suitable as an underlayment for reproduction wallpaper, as long as both liner and paper go directly on the wall.
The reason is that they are much less porous than western-style liners, which are created on a web, have a grain, and are composed of pulp or cellulose fibers. This construction creates a considerable amount of bulk which helps the western-type liners drink up great amounts of paste. Much less of this capillary action takes place with eastern-style papers.
The same objection cannot be made to the “air space” type of installation where a stretched canvas or other fabric is secured to frames. There have been some interesting experiments carried out with eastern papers used as laminates, sometimes on the back of wallpaper, sometimes on the stretched fabric. The distinction is that these installations are properly part of the art conservation discipline, as opposed to the topics here, which are the standard operating procedures for paperhanging in historic homes.
When it comes to acidfree lining paper, the only distinction that elevates it over blankstock is its longevity. Both types absorb paste, help the paperhanger control the installation, and secure the wallpaper far into the future. Acidfree, compared to blankstock, is simply better paper. As long as it’s in the range of 7.5 – 8.5 pH, it is not subject to the acid deterioration which afflicts blankstock after some 15 or 20 years, causing browning, brittleness and decomposition. In this regard, blankstock is similar to newsprint, and indeed, both are made from mechanical wood pulp.
While 15 years is a long time for a regular decorating cycle, historic homes aim for a much longer time frame. This is because a change in decoration is unlikely, and because the cost of reproduction wallpaper usually justifies an upgrade to a better quality liner. The same is true any time a “legacy” type installation is considered, for example, a scenic paper that one might want to keep in the family for generations to come. This topic leads into a discussion about canvas, which allows for removal of such large decorations so they can be used elsewhere, but that discussion will not be broached here.
For both blankstock and acidfree lining papers, a weight of anywhere from 90 to 150 gsm is appropriate (most wallpaper ranges from 100 to 120 gsm).
e. Trimming
For most contemporary work, butt seams are thought to be ideal; the less visible the seam, the better it is judged to be. For work in historic houses, different standards come into play. For most of wallpaper history, an overlapped seam was perfectly acceptable. A butt seam did not become the norm in the U. S. until around 1930 or so. But, even this is a general statement; countries differ widely on what was considered “the norm”, and so did regions within countries.
Despite this history, it’s not quite true that the seams of reproduction wallpaper should stand out: after all, in the period, paperhangers were striving for a seam which was not noticeable at first glance. That explains why they used lining paper (sparingly), trimmed carefully, and hung away from the light. By overlapping away from the light, they ensured that the sun would not cast a shadow when it hit the overlap.
Two complications arise: rag and linen-based wallpapers of the distant past were more fabric-like than today's paper; and, recent research suggests that the weight of wallpaper lessened during the 19th century. Both of these help to explain why overlaps were standard for so long: they were simply not that noticeable. Thus, the question of overlapping is not easily settled. Some of the questions to be considered are: How bulky is the reproduction wallpaper? Will the overlaps call attention to themselves in a way that is not historically accurate? Or, will overlapped seams look “right” for the period?
Trimming and overlapping of the wallpapers should follow 18th,19th, or 20th century models; whatever is most appropriate for the house.
When trimming, the ideal is a slightly wavering edge that, while reasonably straight, shows the hand of the workman (or workwoman) as it overlaps the previous strip. The underlap is also important — these often show in a raking light. Early installations (say, before 1800 or so) show larger underlaps and deckle edges. Later ones show more refined (straighter) underlaps. Three-quarters of an inch is a common historic width for an underlap.
Trimming is done by sitting in a chair with the roll cradled at the feet. One hand begins to take up the roll as the other hand trims the selvedge off. This trimming is done to the pattern, or to a pre-determined point. The work is best done with shears, which are usually somewhat heavier and longer than scissors, with dissimilar finger-holes.
f. Pasting
For pasting, the essential traits are cleanliness and attention to how the paste is spread, especially at edges. Rollers or natural bristle brushes are commonly used. Most reproduction wallpapers are paper-based and therefore highly porous (these notes pertain to paper only). Pasting machines speed the work and may be used as long as they don’t compromise quality.
There are few rules for the strength of the adhesive, because it must be matched to the paper at hand. A common choice is a blend of 50% wheat and 50% cellulose. Both of these powders are high in moisture when mixed, something on the order of 90%. The cellulose contributes flow and helps the paste travel over the paper. The wheat contributes starch, which is tackier and stronger than the cellulose. Wallpapers often need to be pasted twice: the first coat sinks into the pores of the paper, somewhat unevenly, and starts the relaxation and expansion process. The second equalizes the paste film and can be calibrated to what the paper needs — no more, no less.
For water-sensitive inks such as distemper, the paste is not allowed to come into contact with the front of the paper. Distemper types are often pasted full length and brought to the wall with a minimum of folding (booking). For all types, careful folding, carrying, and unfolding at the wall are important. The placement of laser lines and the timing for the installation of each sheet are also important.
The powder types of adhesive already referred to are commercially available, though less so than so-called premix clears, which are the dominant type in most retail outlets. As in the case of “universal” primers, premix clears try to be all things for all types of paper. In this they largely succeed. Many of them are versatile and can hang a wide variety of paper, and can be easily adjusted (thinned) when they’re too heavy.
However, quite a few thin and delicate papers have been damaged through the use of a premix that was too strong or too heavily applied. When it comes to paper, premixes are often unnecessary. If a liner is used, powder adhesives alone can often do the job.
Nevertheless, premixes do have their place in historic houses. First, they can be used almost universally, as covered above. Second, they're very helpful for securing overlaps and borders. Third, many silkscreens have multiple colors, and need additional tack. If the paper has been covered with too much nonporous ink, it begins to behave more like a vinyl than a paper when pasted. Edge curl increases because of differential (the back, which remains paper, is expanding more than the inked front). Because of this, premix clear can be an excellent additive to the powder pastes. Premixes add tack and are good mixers.
Premix clears might even be the only acceptable paste. For example, a wallpaper may be sealed so completely that it cannot be hung with high-moisture, low-tack pastes, even with a liner. Many screenprints answer such a description. If even a premix clear falls short, a clay premix, which is ordinarily used for commercial vinyl, might be called for. In these tough cases, clays are sometimes used as a pre-treatment at seam areas (to increase tack) or, as the primary paste.
g. Hanging
Traditional wallpapers may be printed on soft papers with sensitive inks. If so, they should be installed by pressing the strips against the wall with soft sweeps. In some countries a felt roller is used. If a wallpaper is coated or otherwise more protected, plastic sweeps can be used more freely.
When overlapping strips, the use of guidelines (both horizontal and vertical) from laser levels is highly recommended. Strips which have a wavering, handtrimmed edge can be difficult to hang with chalk or pencil guidelines.
If the wallpaper is washable, seam areas can be sponged lightly after seam rolling, and moisture removed with terrycloth towels or micro-fiber towels. Some re-touching of seams may be necessary, depending on print methods or inks used. Colors used for retouching should be stable and resistant to UV and to color change over time.
A distinction needs to be made between the minor retouching of one or two mismatched items, for example, a twig or a small leaf, and wholesale “improvements” of large amounts of pattern. There are some scenic wallpapers printed from the original blocks in which mismatches abound. No doubt cupping of the blocks over the years has created some distortion, but on the other hand, it’s clear that many of these mismatches must have been apparent when the blocks were new. As such, these mismatches are part of the block printing process — a reminder that wallpaper is not fine art.
In any case, it’s certainly a mistake to improve the match beyond what would have been acceptable in the period. The case is slightly different with Chinese scenics. It seems likely that freehand brush work was more often resorted to (along with appliqué) as a solution. But even here, some mismatches are inevitable. They should not be judged as “flaws.” They, too, are part of the process, as long as the mismatch is not egregious. A reasonable distance from which side-to-side matching may be judged is about 5 to 8 feet.
For Embossed Types: If an embossed wallpaper like Anaglypta is being hung, care should be taken to avoid flattening the embossing, especially at seam areas. Lining paper decreases the amount of pressure needed to make a good join (another advantage of lining paper). Seam rolling, if any is needed, is done by using the edge of a seam roller in a very small path.
h. Other concerns
If historic photos or engravings exist, the paper should be hung according to the historic photos or engravings.
In extreme instances, some embossed papers or flocks will show white edges after dry-trimming. If these would show white on the wall, they should be pre-colored with an appropriate felt-tipped marker prior to hanging.
After installation is complete an installation report should be submitted to the client listing methods and materials used. An inventory should be taken of remaining wallcovering. This report should be filed with at least two departments of the institution, and a copy retained by the installer.
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Photo credit: WallpaperScholar.Com.
The front door area of Martin Van Buren's retirement home, Lindenwald (Kinderhook, New York), is shown in 1986 just prior to the installation of reproduction wallpapers. The date of construction (1797) is engraved on the door knocker. The house was built by Judge Peter Van Ness and became Van Buren's in 1839; it was much enlarged by Richard Upjohn in 1850. One day around 1800 a teenaged Martin used this door knocker while making his rounds as a law clerk for Francis Sylvester. Supposedly.
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