An introduction to “acid-free”, archival materials, and their use in Anthroptic.

You know how that old newspaper clipping you’ve saved since forever has turned brown and crumbly? This happens because newsprint is made of wood and wood contains an acidic substance called lignin. This naturally occurring substance attacks the contents of the paper and degrades it over time. That is one reasons why many artists, especially those who work with paper, often try to use materials that are pH neutral.

Manufacturers of higher quality papers sometimes remove the lignin in wood-based papers and/or “buffer” them with alkaline additives (such as calcium carbonate) to neutralize their acidity. This process also helps to protect them from future exposure to acids in the atmosphere. Cotton (rag) papers are 100% cellulose, meaning they’re a pH neutral product from the start. Cotton papers also have long, strong fibers. This is why US currency is printed on cotton paper and why your bills don’t fall apart when they accidentally go through the washing machine.

The term “archival” is somewhat misleading, as the root of the word means forever. While nothing lasts forever, the goal of many art collectors is to extend the longevity of their pieces for at least a few generations. The fight against time, light, and air is a daily concern for conservators and framers around the country. The easiest way to fight these naturally destructive forces is to use materials that are stable to begin with. But don’t let the materials stop you from buying a work you love; there are numerous ways to protect your piece. A conservator can even de-acidify paper!

For “Anthroptic” we wanted to create something that would stand the test of time. Let’s examine the materials we used and why:

The Box – Binder’s board is made in a single ply which gives it extra strength and durability. The board that we choose has been buffered to give it a neutral pH. However, most binders board still has some degree of instability due to it’s paper content. It is widely evidenced that this does not create a problem. This is because the board used in books is almost completely encased in glue and covered with other (neutral) materials. Therefore any harmful elements do not have access to air to assist in the natural process of breaking down.

The Glue – We used pH neutral PVA: polyvinyl acetate. It is extremely stable and pH neutral. Bookmakers also prize PVA for its transparency, its “stickyness”, and the fact that it remains very flexible even when dry. The other adhesive we used in this book was Daige Rollataq, an acrylic-based adhesive that is also transparent, non-yellowing, and acid-free.

The Paper – The box is lined with pH neutral paper and the folios are 100% cotton rag paper, creating a very stable base for the images and words. The photographs are printed on Epson Heavyweight Matte paper which combined with the pigmented inks we used have a print permanence rating of over 150 years.

Pigmented Inks – With the advent of the digital image, we have come to terms with what paper/printer combinations work well together for lasting durability. As many of us have found out, we can print our digital pictures beautifully on our inkjets, but after they have been on the fridge for even a year, the color has significantly shifted and faded. The inks in most inkjets are dye-based inks. These are the ones that fade rather quickly, even though they come out of the printer looking bright and beautiful. Additionally, commercial digital printers don’t often use high quality papers. You can sometimes extend the life of these images by using higher quality paper, but in general, dyes fade. Pigmented inks have made a big impact in the world of art printing as they are still reasonably affordable and have a much longer life. Wilhelm Research, which specializes in testing the life expectancy of different ink and paper combinations, found that while most dye-based inks have an expectancy of only about 15-25 years, pigmented inks have an expectancy of 75-200 years.



A selected glossary taken from Archival Methods: A resource for archival storage and presentation products

acid – In chemistry, a substance capable of forming hydrogen ions when dissolved in water. Acids can weaken cellulose in paper, board, and cloth, leading to embrittlement. Acids may be introduced in the manufacture of papers and may be lift in intentionally (as in certain sizings) or incidentally (insufficient bleaching). Acids may also be introduced by migration from other materials or from atmospheric pollution. See also pH and acid migration.

acid migration – The transfer of acid from an acidic material to a less acidic or pH neutral material. This may occur directly, when the two materials are in intimate contact. For instance, acid may migrate from boards, endpapers, and protective tissues, as well as the paper covers of books and pamphlets, to the less acidic paper of the text.

acid-free – In chemistry, materials that have a pH of 7.0 or higher. Sometimes used incorrectly as a synonym for alkaline or buffered. Such materials may be produced or buffered. Such materials may be produced from virtually any cellulose fiber source (cotton and wood, among others), if measures are taken during manufacture to eliminate active acid from bleaching, aluminum sulfate from sizing, or pollutants in the atmosphere may lead to the formation of acid unless the paper or board has been buffered with an alkaline substance.

archival; archivally sound – A non-technical term that suggests that a material or product is permanent, durable, or chemically stable, and that it can therefore safely be used for preservation purposes. the phrase is not quantifiable; no standards exist that describe how long an “archival” or “archivally sound” material will last.

binder’s board – A heavy grade of single-ply solid paperboard used for book covers. It is made from mixed paper stock and low grade rags. Davy Board is a brand name. Kappa binder’s board a bookmaking board with no glue between layers.

buffering – The addition of alkaline agents such as calcium or magnesium carbonate during the papermaking process in order to counteract the effect f acidic contamination; the degree of buffering (usually 2-3%) is measured by percentage of paper weight. See alkaline.

burnishing bone (or folding bone) – Smooth, flat, non-abrasive utensil used for smoothing and finishing of mat edges, especially at corners. Also used as a folding and scoring instrument in book binding and box making.

cotton board - Matboard whose pulp originates from cotton which is chemically and physically broken down to fibers and molded into paper stock or board. “Cotton” as a term is usually recognized as a board that is archival and composed of only cotton, as opposed to wood pulp which is, in general, perceived as non-archival when untreated. Also see Rag Board, Museum Board.

cotton fibers – Selected new cotton cuttings acquired from the textile industries. They are free of synthetic fibers and are a source of cotton fibers used in the manufacture of cotton content papers. Basic cotton and cotton linters are also used in the manufacture of pulp.

fiber content - A statement of the types and percentages of fibers used in the manufacture of a paper, board, or cloth. Important because the quality of the fiber significantly affects both the durability and chemical stability of the material.

lignin – An acid organic substance found in wood pulp. It is removed in the chemical pulping process, but is not removed in the manufacture of low grade papers made of ground wood pulp, such as newsprint.

lignin-free - In paper, this term indicates there are only trace amounts of lignin (usually less than 1%). This is desirable because lignin in paper tends to decompose into corrosive and acidic elements.

neutral pH – Exhibiting neither acid nor base (alkaline) qualities; 7.0 on the pH scale. Paper and board stock with a neutral pH are recommended as a storage material for photographic materials.

P.V.A – See polyvinyl acetate.

pH - In chemistry, pH is a measure of the concentration of hydrogen ions in a solution, which is a measure of acidity or alkalinity. The pH scale runs from 0 to 14, and each number indicates a ten- fold increase. Seven is pH neutral; numbers below 7 indicate increasing acidity, with I being most acid. Numbers above 7 indicate increasing alkalinity, with 14 being most alkaline. Paper with a pH below 5 is considered highly acidic. Buffered storage materials typically have a pH between 7 and 9. See also acid; alkaline.

polyvinyl acetate – A plastic usually abbreviated as PVA. A colorless transparent solid, it is usually used in adhesives, which are themselves also referred to as PVA or PVA adhesive. There are dozens of PVA adhesives, some are “internally plasticized” and are suitable for use in conservation, due to greater chemical stability among other qualities.

rag content – 1. Paper that is made chiefly from linen or cotton fibers rather than from wood pulp, which is highly acidic. High rag content usually indicates a neutral pH. 2. A term that indicates the presence of cotton fibers in a sheet of paper. The content can vary from 25% to 100%.

rag paper – Cotton fiber paper. It is made from cotton cuttings and linters.

wet-mount – The technique of gluing artwork to a support with water-based adhesives.

wood pulp - Prepared for papermaking from trees of various kinds. The process of manufacture includes two distinct classes: (1) mechanical wood pulp or ground wood from which newsprint is made; (2) chemical pulp, produced by various methods, which is a higher grade since more lignin and other impurities are removed.