Restoration & Preservation
A short history of paper
The remote origins of paper may seem unrelated to clock restoration, but understanding how the production of paper evolved and changed over the centuries helps to clarify why some clock labels that are over 200 years old appear relatively in tact while many much newer labels are terribly deteriorated. This understanding is the first step in developing an effective means to restore and preserve clock labels.
When we think of paper at its earliest we usually think of Egypt. It was almost 5000 years ago when a marsh grass called Cyperous Papyrus was first harvested and carefully woven into a fine matt.
It was then allowed to dry in the sun and subsequently used as a writing surface.
The papyrus tablets found in tomb excavations, while similar to paper in usage, are actually closer to cloth fabric than to what we consider paper.
The first documented evidence of true paper making dates from around 105 A.D. in China. T'sai Lun, chief eunuch to Han dynasty emperor Ho-Ti, experimented with a wide variety of plant material and found a technique for soaking and agitating the fiber until each strand was separated.
The fibers were mixed with water then a silk-screen was carefully lifted up through the water/fiber mixture. The captured fibers were allowed to dry producing a very thin layer of interwoven fibers; the first true paper.
Papermaking remained a secret in China until around 700 A.D. when Arab nations, then at war with China, captured an entire town of papermakers. The captives were taken back to the middle-east and forced into papermaking.
It wasn’t until the time of the crusades (around 900 A.D.) that paper making techniques arrived in Western Europe. Until that time the preferred medium for the creation of documents was smooth parchment produced from animal skins. Unfortunately, parchment was extremely expensive. It has been estimated that a single hand-written bible of the time required the skins of more than 300 animals.
In 1456 Gutenberg perfected the movable-type printing press and produced his famous bible. His invention spawned an explosion in book making and the demand for paper.
Paper in Gutenberg’s time was made from discarded linen (flax) and canvas (hemp). The explosion in demand for paper would have easily outstripped available materials except for a cruel coincidence. The rise in demand for paper occurred, oddly enough, just at a time when the plague or black death was killing millions of Europeans. This yielded thousands of tons of clothing and rags that were subsequently used in paper making.
By the 1700’s the increase in literacy produced such a demand for printed books that it did outstrip the availability of rag material. The shortage was so acute that there were actually “rag-wars” in the mid-century. Nations passed laws forbidding rags to be taken out of the country and in England it was forbidden to bury a person in anything but wool.
Throughout much of the century there was an intense search for an alternative to rags for papermaking.
French scientist, Rene de Réaumur (1683~1757), wrote of his observations of wasp chewing wood then spitting out the resulting mush to build nests. Réaumur noted that the wasp appeared to be making paper from wood pulp. Unfortunately Réaumur never got around to actually trying to make paper from wood. He had however stumbled upon the secret to practical papermaking.
Invention of the cotton gin in 1794 provided higher production of cotton cloth and a new source for cloth and rags, but the demand for paper continued to outstrip availability.
As wood pulping technology improved, prices fell and the demand for paper grew quickly. Newspaper companies both small and large sprang up all across the country and consumed vast quantities of pulp paper. Clock makers, then at the height of their production volumes, added considerably to the consumption of low cost paper.
By the mid 1850's there
were almost 200 paper mills in the United States. Newspapers and
paper making are often considered key factors in the transformation of
the country from an agrarian to industrial
Why Labels Deteriorate
In the long history of paper, one technical item stands out; Paper which had been made of rags for over 1000 years began to be made from “cellulose” or wood fiber. This event brought a much needed cheap, renewable source for paper but it also brought some negative aspects which continue to plague document conservators (and clock restorers) even today.
Rag paper depends on a mechanical bond between the millions of cloth or rag threads. Close examination of early rag paper using a magnifying glass will reveal interlocked fibers which are often 1/2 inch long or longer. These long fibers mechanically lock the paper together into a sound, durable sheet.
It is not uncommon to come across clocks or documents from the late 1700’s or early 1800’s and notice that the paper appears to be is quite good condition for its age. Often, the yellowing or browning commonly seen on old paper is missing and the paper retains much of its original whiteness. The reasons for this are twofold. First, rag paper is very strong and durable due to the long fibers used in its manufacture. Second, rag paper was produced using little more than rags and water.
Consider the life cycle of a rag or cloth. The cotton ball is harvested, it is spun into thread, woven into cloth, cut and sewn into clothing. All along these stages the material is washed for one reason or another. During the life of the clothes the garment is subject to periodic washing. Finally, when the worn clothing is discarded for papermaking, it is once more washed prior to its disassembly and rebirth as paper. All of this washing of the fibers has the effect of removing most, if not all, of the natural resins and active chemicals in the fibers. As a result, the paper produced from rags tends to be pH neutral or non-acidic. The neutral pH combined with the long fibers cause the paper to remain stable over extremely long periods.
The pulp paper, introduced in the mid 1800’s, unlike rag paper, uses the cellulose of finely ground wood as its primary content. The pulping process creates very small (and short) cellulose fibers. The cellulose is too short to create strong mechanical bonds and uses, instead, a chemical bond at the molecular level.
Water molecules have one large oxygen atom linked with two smaller hydrogen atoms. Water molecules chain together on the surface where the hydrogen atoms are shared. This causes the effect called surface tension. This chaining process at the molecular level is the key to making cellulose paper.
The structure of cellulose is such that it readily chains with water molecules. When cellulose is suspended in water it is included in the water chain creating a molecular level bond between the water and cellulose. The water/cellulose mixture is then captured by the papermaker’s screen and allowed to dry. When the water is removed from the equation the remaining cellulose is chained together in a molecular bond. This molecular interaction of cellulose provides a strong bond even though the individual cellulose fibers are very short. This bond should provide a very strong and stable paper and it would except for one factor: the pH.
The process of grinding wood chips in water to produce cellulose does nothing to remove any of the saps and chemical compounds that are a natural part of the tree. They remain with the water/cellulose mixture that is used to create paper. Unfortunately, these chemicals tend to have a very low pH reading and thus are very acidic.
Pulp based paper is acidic at the time of its production. However, the acid level gradually becomes higher as impurities in paper such as lignin, hemicellulose, hydrolyzed cellulose oxidize. Decomposition of lignin produces a strong organic acid and also promotes the absorption of atmospheric acid.
Acids are oxidizers. That is they break down molecular bonds to release oxygen. That is exactly what occurs with pulp based paper. Over time, the acids in the paper erode and destroy the cellulose bonds and the paper literally disintegrates. An excellent explanation of the chemical interactions causing degradation of paper can be found at the Preservation and Care of Philatelic Materials web site http://www.stamps.org/care/pcpm.htm#TOC
Clocks produced from the mid 1800’s almost all had labels made from pulp-based paper. Clocks from the 1700’s and early 1800’s usually used rag-based paper for their labels. Therein lies the reason that many labels from early wooden-works clocks appear to be in much better condition than the labels in clocks produced 50 to 75 years later.
The foremost challenge in preserving clock labels for antique American clocks is finding a means to neutralize the acidic nature of the paper. Once the chemical degradation of the label is arrested steps can be taken to further preserve what remains. Chapter 8 of Extreme Restoration provides methods to measure the acidity of a label then effectively reduce the acidity to an acceptable level. Once the acidity has been addressed, there are a number of techniques that can be used to restore and stabilize the paper. Finally, the correct and incorrect materials to use for covering and protecting the label are discussed.
Clock labels are an important part of the clock that provide a wealth of information about the clock and its maker. Proper preservation and protection of labels is one of the most important things a restorer can accomplish.