Conservation work on the Peter H. Raven Library’s copy of The Orchidaceae of Mexico and Guatemala has begun! Follow along as we document this painstaking restoration of one of the largest and grandest volumes in the Garden’s rare book collection.

The Pages of Books Can Tear and Chip

Paper is generally a very stable substrate for printing and writing, but several factors can make paper more likely to become brittle, leading to rips and losses.

• Papers can be made of poor materials. The best papers are made of plant materials that have a high percentage of cellulose, a stable carbon-based compound whose chemistry makes the formation of a sheet of paper possible. In Europe and America, the best plant materials available have been cotton and linen in the form of rags. In Asia, excellent paper-making plants have included the paper mulberry (Broussonetia papyrifera) and gampi (Wikstroemia canescens). In the nineteenth century, papermakers began using wood pulp, which does not make good paper as it contains a lot of non-cellulosic material, such as lignin and hemicellulose. When these impurities are present in paper, it becomes yellow and brittle.

• Papers can be made with harmful additives. The most common additive is sizing, a protective material added to paper to make it less absorbent. Sizing makes it possible for us to write and paint on paper. The traditional size for European and American papers has been gelatin made of the bones and skins of animals. It was cooked into a liquid solution and brushed on paper where it dried and formed a tough, strong surface. When Europeans and Americans started making paper on machines (early 19^th century) the sizing changed from gelatin to rosin mixed with alum, an aluminum salt. Alum is harmful to paper, causing it to become brittle and discolored.
• Papers can be stored in bad conditions. Cellulose is a generally stable compound, which is why papers that are almost 100% cellulose can last for hundreds of years, but even good papers can degrade if stored in bad conditions—high temperatures and humidity (sounds like Saint Louis in the summer!). Even worse are situations in which both temperature and humidity fluctuate wildly up and down. These conditions push chemical change and can cause embrittlement and yellowing.

Bateman Has Paper Problems

The Library’s copy of Bateman’s Orchidaceae of Mexico and Guatemala contains a lot of ripped paper, especially towards the front of the book. On some leaves, sections have fallen out, leaving holes, especially along edges.

We don’t yet know why some of the paper in Bateman is in poor condition. Since the paper is probably not made of wood pulp (1830s/40s is too early for wood pulp paper), the problem could be the sizing and/or historical storage conditions.

No Matter What Caused the Problem, We Still Have to Fix It

Book and paper conservators routinely mend paper, so the materials and processes that we use are well-established and tested.

We use Asian-style papers made of the paper mulberry or gampi to patch rips. These papers have a record of strength and chemical stability that goes back for thousands of years. They are also less heavily processed than Western style papers, which leaves them with longer fibers, which in turn makes possible the creation of thin, strong papers.

Paper conservators can put this paper right on top of text, and it becomes practically invisible.

We cut or tear out strips of this paper and then adhere it over the rip.

The adhesive we use is a purified wheat starch.

Starch, especially wheat starch, is a good adhesive for paper conservation. It is strong (which you know if you have ever made paper mache), it is chemically stable, and it can be removed with a little moisture. In other words, it is reversible.

Reversibility

Conservators try to make all treatments reversible; in fact, reversibility is written into our ethical guidelines.

Why is reversibility so important? There are several reasons.

• Best practices can change as new materials and techniques become available.
• Scholars may need to see the artifact in its original condition, without repairs.
• The repairs may, over time, prove harmful in some way to the artifact, despite the best efforts of the conservator.

Mending the paper in Bateman’s Orchidaceae (like cleaning the paper) will take several months.

NEXT UP: Testing the paper to learn about is chemistry

Learn more about the restoration of the Bateman book:
Part 1 | Part 2 | Part 3 |Part 4 |Part 5 | Part 6 | Part 7