Clients are often surprised to learn how dynamic and changeable paper can be. Like many of the porous materials conservation framers work with (rag board, wood, etc.) paper is hygroscopic, meaning that it expands and contracts with changes in humidity. How exactly paper reacts to moisture depends on numerous factors: it is produced by a number of different methods from a wide range of materials, processed and stored in many different ways, and affected by the processing and materials that the artist brings to bear on it, as well. Many papers are highly sensitive and reactive to moisture, expanding greatly in response to it.
In conservation framing there is no attempt to control or prevent the natural tendency of paper (or any other material) to move, expand, or otherwise change. Such an attempt would inevitably fail and the problems would be made worse, resulting in direct harm to the paper. Conservation hinging and framing make allowances for the personalities of materials like paper, rather than trying to exercise control over them.
Conservation HingingHinging is the heart of conservation framing, because hinges are the only part of the frame that are attached directly to the work of art.
Conservation hinges don't come in a package and don't come with pre-applied adhesive. It doesn't matter who makes the packaged hinging material or what the package says — packaged hinging is not conservation hinging. And even though manufacturers of such hinges may claim they are acid-free, they may well contain acid, or develop it over time.
True conservation hinges are handmade from materials that are carefully purchased from a reliable supplier and custom-designed for each work of art. The hinger starts by assessing the qualities of the artwork, such as weight, translucency and reactivity to moisture and color. Based on this assessment the hinger chooses from a wide range of papers (generally Japanese mulberry papers). The hinger custom tears each hinge to size, carefully feathering the edges.
The adhesive is also custom- and hand-made. The hinger starts with raw materials from a reliable supplier, to ensure they contain nothing other than vegetable starch. The adhesive, which is made in small batches so that it can be used almost immediately, is applied first to the hinge. It is allowed to dry to a certain point before the hinge is applied to the artwork. Immediately after this application the hinger uses a process of desiccation to draw moisture out through the back of the hinge, thus exercising as much control as possible over the amount of moisture going into the artwork. This meticulous process is designed to minimize the occurrence and severity of puckering at the site of each hinge, and to maximize reversibility in every way.
In positioning hinges, the hinger doesn't seek to control the behavior of the paper. In other words, hinges won't be used to help the artwork look flatter in the frame. The reasons for this are first that it won't work and, second, that it is dangerous. Hinging can't control paper and over-hinging, stretching paper on hinges and placing hinges at the bottom of a work all have potential negative consequences that far outweigh even the imagined advantages--advantages they don't actually deliver.
For example, the most common mishap a framed artwork faces is for it to fall, landing on the bottom edge of the frame. Conservation hinges, placed at the top, are designed to roll away from the work's backing in this situation. This is a purposefully-engineered shock absorbing function that can actually prevent the force of the blow from being directed at the artwork, itself, resulting in creases or tears. In such a situation, bottom hinges are disastrous. They not only interfere with the ability of the top hinges to let go, but keep the artwork attached at the bottom while the weight of the paper pulls around and against them — resulting in further tears or creases.
But even without this kind of accident, over-hinging and bottom-hinging result in mechanical problems that ultimately make the artwork look bad and possibly harm it. This is because both the artwork and the museum board to which it is hinged are continually expanding and contracting with changes in humidity. When an artwork that is hinged at the bottom shrinks, the paper gets stretched, producing unsightly furrows or even tearing. When the artwork expands, it pushes against the hinges, bellying out toward the glazing, and can easily crease or tear.
For all these reasons, the ideal condition for a work on paper in a picture frame is to be hanging like a drape, attached only at the top. Nonetheless, there are good and appropriate exceptions to these principles. For example, sometimes side tabs are called for. They are governed by strict rules of placement and are generally attached more loosely than the top hinges. Most exceptions to the principles of conservation hinging are relatively rare, to be addressed on a case-by-case basis.