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Conservation Procedures
7.4 How to Do Your Own Matting and Hinging

When matting paper artifacts, using the right materials is essential. Paperboards for mounting must be chemically stable with good aging properties. These are the so-called archival-quality, or acid-free, boards sold by conservation suppliers. They are free of lignin and are pH neutral or, more often, slightly alkaline. It is also important to choose the methods and materials for attaching the artifact to the mount are also important. The traditional method is to hinge the object with Japanese paper and a starch paste. More recently, corner supports or edge strips have come into favor since these can be used without applying adhesives to the object.

Window Mats

A window mat is the customary mount for a work of art or valuable artifact on paper. A mat is composed of a top sheet with a window and a backboard (see Figure 1). The two boards are held together with a strip of cloth tape along one edge, usually the top. The window permits the object to be seen while the mat protects it from handling and isolates it from surrounding materials.

In the past, museum-quality mats for works of art were expected to be made of rag fibers, that is, cotton or linen. Today ragboard is still favored by museums, but some lignin-free, wood-derived boards are now accepted by the preservation community. Mat boards of either type are usually buffered with an alkaline material to neutralize any acids they may absorb as they age. It is important to confirm the quality of the board with the supplier and by reading descriptive material provided by the manufacturer.

Four-ply board is the thickness most often used for matting. Larger works of art or those with undulations or raised elements such as seals may require a thicker board for the window portion of the mat. Boards heavier than four-ply are available from conservation suppliers, or they can be made by laminating two or more four-ply boards. Sink mats may also be used (see Figure 3). These are constructed by adhering strips of conservation board to the backboard to make a recess, or "sink," in which the object is mounted. The sink construction is hidden by the window portion of the mat.

Mats can be ordered from any framer, but making them yourself can save money. The tricky part is learning to make a neatly cut window opening, which is usually beveled (cut on a slant). This is best learned by practicing with an experienced technician.  With practice, a skilled person can make a beveled window with a simple utility knife, but a mat cutting device greatly simplifies the procedure. There are a number of mat cutters on the market. The best of these are the easiest for an inexperienced person to use. Such mat cutters are expensive but will pay for themselves if cutting mats is to be an ongoing activity.

Hinging

Hinging is the customary way to mount an object in a window mat. The artwork is hinged, usually with Japanese paper and starch paste, to the backboard of the mat, never to the reverse of the window.  This keeps an object stationery when a mat is opened and avoids potential damage from encountering an object attached where it is not normally expected to be.  As shown in Figures 1 and 2, part of the hinge is attached to the object and part to the backboard. Hinges allow the artwork to be removed easily from the board if that becomes necessary. Under no circumstances should the object be adhered directly to the mount. Alternatives to hinging are suggested toward the end of this leaflet.

Papers for Hinging

High-quality Japanese papers, sometimes referred to as mulberry papers, make effective hinges because they are strong without being bulky and do not discolor or weaken with age. Traditionally these papers were made by hand, but now Japan exports machine-made papers of suitable quality. They are available in different weights and under a variety of names. The names are not specific and do not guarantee the fiber content of the paper. Some Japanese papers contain wood pulp and are not appropriate for conservation purposes. To be safe, use sheets made of 100 percent kozo fibers and buy them from conservation suppliers, not general art or paper suppliers.

Hinges should have torn edges. Tracing an incised line in the paper with a wet artist’s brush allows you to pull the paper apart to create an evenly fibrous edge. A torn edge creates a less obvious hinge attachment, especially on thin or transparent papers.

Types of Hinges

Figures 1 and 2 show two common types of hinges. Folded hinges (Figure 1) are tucked out of sight under the object. They must be used when the object is “floated,” i.e., when the edges of the artwork are visible within the window. Pendant hinges (Figure 2) use two pieces of paper that form a T. The bottom of the T is adhered to the reverse of the object. The top is attached to the backboard, often with a cross piece for added security.

 

Placement, Size, and Number of Hinges

Hinges are usually placed at the top edge of the work of art. If the object is small, a hinge at each upper corner provides adequate support. Larger objects or those on heavy paper require additional hinges evenly spaced along the top edge. If the object is to be floated, additional hinges at the bottom corners or along the edges are desirable. Large sheets that tend to curl may require several small hinges on each edge if they are floated.

The number and size of the hinges as well as the weight of the hinge paper depend on the weight and size of the object being mounted. If the mat covers the edges of the object, thereby helping to hold it in place, fewer hinges are needed. Hinges should be small, less than three inches across. The part of the hinge that is adhered to the object should extend less than 1/2 inch into the sheet. Use several small hinges rather then a few large ones. Large hinges or a strip across the top edge may restrict the natural movement of the paper in response to environmental fluctuations and encourage rippling.

Adhesives for Hinging

Adhesives for hinging must have three qualities that remain constant over time:

  • Sufficient strength: The adhesive must hold for an indefinite period.
  • No tendency to discolor: It should not yellow or darken.
  • Reversibility: It must remain readily water soluble so that the hinge can be
    removed with a minimal amount of moisture, even after several years.

Few, if any, commercially available adhesives meet all these criteria. Staining from self-adhering tapes and from adhesives such as rubber cement and animal glue is frequently seen by conservators. There are commercial adhesives that do not stain, but these usually are not permanent or easily reversible. The “archival” self-adhesive tapes sold by conservation suppliers are probably more stable than other commercial products. However, because their aging properties are not yet known and conservators usually have to resort to organic solvents to detach them, they are not recommended at this time for objects of value.

Conservators recommend starch paste or methyl cellulose.  The paste is homemade from pure starch extracted from flour, usually wheat or rice flour. This starch is available from conservation supplier vendors. A recipe for starch paste follows, as well as directions for making paste in a microwave oven.

Starch Paste

  1. All utensils used for paste making must be spotlessly clean. They should not be used for other purposes, least of all food preparation. They should not be cleaned with soap, however, which may contaminate the paste.Place one part wheat or rice starch and four parts of distilled water in a saucepan or the top of a double boiler. The cooking vessel should be enamel-coated, stainless steel, or Teflon-lined, not aluminum.
  2. Mix well and allow the mixture to stand for 20 minutes before cooking.
  3. Cook on medium-high heat, stirring constantly with a clean nonmetallic utensil.
  4. When the paste begins to thicken (this may not happen right away), reduce heat and continue stirring. As it thickens, the paste will become stiffer and more difficult to stir.
  5. Stir until the paste is thick and translucent. It usually takes about half an hour to reach this stage.
  6. Remove from the heat and continue stirring for the first few minutes of cooling.  Transfer the paste to a clean, covered container and allow it to cool. Paste must be cooled to room temperature before it can be strained and used.
  7. Straining and thinning is necessary because the paste becomes hard and rubbery when cool. Strain as much as you will need just before using. A strainer with tiny holes or a Japanese paste strainer (available from conservation suppliers) can be used.
  8. Brush the strained paste against the bottom of a container while mixing in distilled water a little at a time until the paste reaches the consistency of mayonnaise.  It is important to add the water gradually so that the paste does not separate out into clumps.

Because refrigeration may cause the paste to lose its tack, keep it at room temperature. It is best to make small batches, since the paste does not usually keep for more than a week. A preservative can be added, but these chemicals are toxic and not recommended.

Microwave Wheat Starch Paste

University Products, a supplier of conservation materials, publishes a quick, easy paste recipe in its catalog. This is ideal if paste is used only occasionally and in small quantities.  Strain and dilute the paste beofre use, as above.

Place 1 tablespoon of wheat starch in a clean, microwave-safe container, add 5 tablespoons of distilled water, stir, and place the mixture in a microwave oven. Microwave on a high setting 20 to 30 seconds, remove the paste, and stir. Place it back in the unit and microwave it another 20 to 30 seconds. Remove it and stir again. Repeat this process several times until the paste is stiff and translucent. If larger quantities are made in the microwave oven, increase the cooking time between stirrings. Paste should be cooled to room temperature before it is strained and diluted for use.

Another Simple Paste: Methyl Cellulose

Methyl cellulose, the main ingredient in most commercial wallpaper pastes, is acceptable for conservation purposes if used in its pure form. It is available from conservation suppliers as a white powder and does not need to be cooked. Add 1 rounded tablespoon of methyl cellulose powder to 1/2 cup distilled water, stir, and let stand for several hours. Thin to the consistency of mayonnaise with distilled water. Methyl cellulose absorbs water slowly so dilution takes a few minutes.  Methyl cellulose is not as strong as starch paste but should give adequate support for objects of moderate size. It keeps for several weeks and does not require refrigeration.

The Hinging Procedure

Before hinging, assemble the following:

  • The finished window mat
  • Hinging paper (Japanese kozo) torn or cut in appropriate sizes
  • Starch paste in a small dish, thinned to the consistency of mayonnaise
  • A flat artist’s brush, ideally 3/8 to 1/2 inch wide
  • Pieces of clean, white blotter, about 2 by 3 inches
  • A larger blotter to serve as a substrate for pasting
  • Small pieces of spun polyester (Hollytex or Reemay), the same size as the blotter pieces.  Spun polyester is available from conservation suppliers.
  • Several weights, at least one pound each (two pounds is better). Lead weights with a flat surface can be covered with cloth. Fishing weights or bags of lead shot can also be used on top of small pieces of glass or rigid acrylic.
  • Archival tape for securing the top of the hinge to the backboard (for example, Lineco Framing/Hinging Gummed Paper Tape)
  • Tweezers or other implement for handling pasted wet hinges

Attaching the Hinges

  1. Make the mat first. Attach the window portion of the mat to the backboard with a strip of cloth tape so that the window and backboard are aligned.
  2. Place the object to be matted face down on a clean surface.
  3. If pendant hinges are used, brush starch paste on one edge of the tab (the part that will adhere to the reverse of the object) on a piece of blotting paper to absorb excess moisture. Apply the hinge to the reverse of the object and, once in place, tamp it lightly with blotting paper or other absorbent material to further remove excess moisture. Place a piece of nonwoven polyester (Hollytex or Reemay) to prevent sticking and then a small blotter and weight over the hinge and leave until the hinge, is completely dry. Changing the blotter after the first few minutes will speed the process as will drying the blotters for a few seconds in a microwave oven before using them.  This also reduces the risk of cockling or staining the paper because of moisture. Allow at least one hour under weight for hinges to dry completely.
  4. Repeat the application of hinges wherever needed, always at the upper corners at least.
  5. Place the object face up on the mat backboard and check that it is centered in the window. Weight the object so it does not move. Be sure to protect the face of the object with a piece of blotter under the weight.
  6. Open the mat and attach the top of each hinge to the backboard as shown in Figure 2.   In the case of folded-under hinges, small pieces of polyester or Melinex should be placed inside the hinge to keep it from adhering to itself during drying.  Weight the hinges as before for a good hour until they are completely dry.  Remove the inserted polyester or Melinex pieces.

It may take time before hinging comes easily, but practice pays off.

Mounting without Hinges

In recent years some institutions have been reluctant to apply adhesives to artifacts, especially if they are valuable. Mounting without adhesives can be done with corner supports or edge strips.

Small corners of chemically stable plastic (polyester film) or archival paper are commercially available for mounting photographs. Although photo corners work well for many photographs and for small works on paper, they are too small to support larger objects. Larger envelope corners (made from folded paper) or strips across the corners give better support, but they cannot be hidden under the mat unless the object has wide margins.

Hugh Phibbs, coordinator of matting and framing services at the National Gallery of Art in Washington, D.C., has developed innovative ways of mounting without adhesives.  Generally speaking, these methods involve supporting the object on the mat with strips of archival-quality paper that are folded over the edges of the object to hold it in place.  The strips are adhered to the backboard at their extremities. Phibbs gives workshops periodically, and his ideas appear in a monthly column in Picture Framing Magazine. Some of these articles are cited below.

Suggested Further Reading

Munro, Susan Nash. "Window Mats for Paper Objects." Washington: National Park Service Conserve O Gram 13,1:(1993).

Phibbs, Hugh. "Preservation Matting for Works of Art on Paper." A Supplement to Picture Framing Magazine (Feb. 1997).

__. "Reinforcements for Support Strips." Picture Framing Magazine (Jan. 1998). 

___. "Stable Support for Overmatted Artwork." Picture Framing Magazine (Dec. 1997).

Smith, Merrily A.  Matting and Hinging of Works of Art on Paper. Washington, D.C.:Library of Congress, 1981.

 

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