(Excerpts from ART HARDWARE: The Definitive Guide to Artists’ Materials, by Steven Saitzyk © 1987)
An archive is a place to keep records. Archival refers to something used in storing and preserving such as archival boards, which are used for storing and keeping artwork and records. The qualities that make a board safe for storing artwork and valuable documents have been evolving since the mid 1970s. The most desirable board is one that does not age, remains at a pH of 7, is totally inert, is iron- and copper-free, is inedible to insects, remains free of mold and mildew, does not condense moisture, yet is absorbent. The development of such a board is unlikely for many years. A more reasonable expectation for an archival board would be that it is composed of either 100 percent purified cellulose from wood or 100 percent rag (or cotton) fiber and that it is at least 50 pt. thick. It should also be free of iron and be buffered to remain free of acid for seventyfive to one hundred years under normal framing and storage conditions.
The logic for this is that a board made from cotton, rag, or purified wood cellulose is relatively inert, does not readily condense moisture, and is practical in that it can easily be cut to size. The thickness is important because it provides both a mechanical and a chemical barrier. Thicknesses of less than 50 pt. may not be sufficient to keep a moderate-size piece of art (26″ X 36″ or larger) away from the glass facing when it is framed. This is important because there is a natural tendency for artwork that is hinged to a mat, rather than glued to a backing, to curve toward the glass. Boards of less than 50 pt. are more easily subject, with changes in humidity and temperature, to developing buckles that can be transferred to the artwork that is being stored or framed. The same thickness is also needed to provide a chemical barrier from the acids present in polluted air and from such other storage materials as the backings used in framing or the wooden file drawers used for storage. Buffering of the board is mandatory, with the exception of boards made for the storage of albumin, dye transfer, and Cibachrome prints so that any acids from the storage environment and air pollution can be neutralized. Care must be taken by the manufacturer to be certain that there is no residual iron in the board that may accumulate in the washing of the fibers during processing.
Any board that can meet these requirements and show no detectable deterioration for seventy-five to one hundred years should be considered safe and probably would remain safe for several more generations. The type of museum board currently in use has not been around for one hundred. years, and all claims to permanency are based on theory and accelerated aging tests. In other words, everyone is attempting to make the best decisions possible with whatever information is currently available. It can be expected that new definitions and minimum requirements will continue to evolve.
“Museum board” is the common name for 100 percent rag or cotton-fiber boards that meet the current minimum standards for archival use. Museums were among the first major users of this type of board for storing and framing artwork, hence the name. At one time, this board was also called rag board. Because there are several types of boards that contain rag or cotton that do not meet the minimum standards for archival use, the name has slowly been replaced. Despite the introduction of conservation boards composed of purified wood cellulose, museum boards are still overwhelmingly the board of choice for archival purposes, because rag or cotton fibers are longer than those of purified wood cellulose and are, therefore, stronger and more durable. Any picture framer knows that it is much harder to cut a mat from a museum board than a conservation board, and that cutting blades wear twice as fast when cutting a museum board.
Several manufacturers produce a limited selection of colored museum boards. The Strathmore Paper Company, for example, manufactures two grays, five colors, black, white, natural, and cream, all .tested for bleed resistance, scuffing, rubbing, and abrasion to meet standards established by the United States Library of Congress. The thickness of its four-ply boards was originally between 50 and 55 pt.; however, Strathmore has increased it to 60 pt. to compete with the thicker boards now on the market. Museum board of a one-ply thickness between 12.5 and 15 pt. and usually available only in white-is used primarily for temporary storage and as a separation sheet when stacking artwork. It is also occasionally used as a drawing paper. Museum board that is two-ply can often be found in the same range of size and color as that of four-ply, and is used for temporary storage for up to twenty-five years. It is too thin to be used in picture framing as either a mat or a backing. Both one-ply and two-ply are available in only 32″X40″.
Museum board that is four-ply is most commonly used for long-term storage and museum-style framing. It is available in various shades of white and gray, as well as a limited range of colors, in 32″ x40″, and is also made in 40″ x60″. A new, still larger size, 48″ x84″, has begun to be distributed in some major cities. New and not readily available, six-ply and eight-ply are, in most cases, chosen more for aesthetic reasons in picture framing than for additional protection.
Rag Mat Boards
Rag Mat is a 100 percent rag board with a buffered, fade-resistant, colored, sulfite-pulp paper facing. It is produced by the Crescent Cardboard Company. It is currently manufactured in twenty-eight colors, and new colors are soon to be introduced. The boards are available only in 32″x40″.
The early versions of this board had a thickness of approximately 45 pt., which was considered by many people to be too thin to keep most medium-size paper artwork away from the glass in picture framing. These boards are, however, being replaced with ones that are 50 pt. Rag Mat “100” is similar to the Strathmore museum boards, which are now produced in a thickness of 60 pt. in four-ply.
These boards are made neither from rags nor from cotton, but are composed of purified cellulose pulp from wood where the lignin has been removed and to which an alkaline buffer has been added. Conservation boards are made to meet the same requirements as those for museum boards, and are accepted by most institutions for use in archives. Some conservative conservators still question this type of board for long-term use because of the extensive chemical processing that the fibers undergo. They believe that the fibers are significantly weakened, affecting durability and possibly even permanency. Nonetheless, as rag and cotton fibers become increasingly rare and expensive, conservation will become more common.
A large percentage of conservation boards available at this time are produced by three companies-the Rising Paper Company produces Conservamat, Andrews Nelson & Whitehead offers pHase 7, and the Process Materials Corporation offers Archivart Conservation Board. With the exception of the white and cream produced by the Process Materials Corporation, these boards are all between 50 and 60 pt. in thickness and 32″X49′ in dimensions. Larger and thicker sizes are not generally available.
The color selection of conservation boards is much the same as the limited selection of museum boards, although black is not available. At one time, the gray pHase 7 boards used for framing changed significantly after a year or two, becoming lighter and developing a red tint. Today, primarily due to intense competition, most manufacturers apply stringent tests to avoid such problems as fading. These tests, however, are accelerated aging tests, which only simulate certain aspects of the aging process and therefore cannot be a substitute for actual conditions.
The leading conservation mat board, Alphamat, made by the Bainbridge Company, is the conservation board equivalent to Crescent Cardboard’s Rag Mat. Alphamat is available with paper facings in sixty colors, which are pigmented to prevent fading. The board itself is a bright white. The bright white bevel, although eye-catching on white and off-white mats, is found by many people to be distracting on the darker and more strongly colored shades of mats. This board is designed for use in picture framing where the artwork is not touching the paper facing. Although several pastelists have used this board surface to draw on, it is not clear whether it is generally safe for fine artwork. The surface is a very thin paper adhered to an archival board and this combination would appear to be less hazardous than using a colored wood-pulp paper alone because, over the years, as the paper facing loses its strength, it has the board for support. In addition to the sixty colors available in 32″x40″, nine are produced in 40″ x 60″, but are not readily available. The boards are 55 pt. thick.
Archival Nonbuffered Boards
Albumen photographs, which were made through an early method of producing black-and-white prints with animal protein, and dye transfer prints, produced by a more modern and lightfast method of producing color prints, are both adversely affected by an alkaline pH, or a pH of more than 7.5. Dyed natural fibers, like silk and wool, are also sensitive to alkalinity because the dyes used in their production are usually acid dyes. It is therefore best to avoid buffered museum and conservation boards when framing albumen photographs, dye transfer prints, and work made of natural fibers.
Nonbuffered archival boards are very specialized, and are not readily available. The Light Impressions Corporation, however-a mail order house that sells a large variety of archival supplies to the public as well as to the trade-offers a 50 pt., four-ply, 100 percent rag board that is not buffered, in sizes from 8″ x 10″ to 32″ x 40″. The company’s address is: 439 Monroe Avenue, Rochester, New York 14607.
Archival Corrugated Cardboard
The Process Materials Corporation produces a buffered corrugated board that appears identical to ordinary corrugated board, except that it is blue-gray or bright white rather than brown. It is called Archivart Multi-Use Board, and is available in both single weight (single wall), and double weight (double wall), in sizes of 32″X48″, 40″X60″, and 48″X96″.
Archival corrugated cardboard is used as a backing board in museum-style framing and storage, as well as an artists’ material. Although the purity of the wood pulp used to make this board is questionable, as is the quality of the adhesive used to hold the various layers together, the manufacturer claims it meets archival requirements. For additional security when using the board as an art material, I have had good results in creating rigid, and safe, painting surfaces by mounting 100 percent rag to this board.
(Excerpts from ART HARDWARE: The Definitive Guide to Artists’ Materials, by Steven Saitzyk © 1987)