Conserving the Papers
The Dinwiddie documents consist of writing in iron-gall ink on handmade European papers. As the ink ages, acids and metals within the ink corrode the paper. The first visible sign of ink corrosion is "ink burn," characterized by ink burning through the front of a page and becoming visible on the back. Ink burn degrades the paper and causes mechanical damage, such as tearing and loss of paper.
The goal of this conservation project was to stabilize the documents by removing soluble corrosive metals and acids that destroy the paper. This was achieved by washing the paper in a series of alkaline baths and replacing the original protective gelatin sizing. After the paper was strengthened, tears were mended and fragments were reattached.
The steps of the conservation process are described below:
Step 1: Testing the inks
The ink is first tested with non-bleeding iron (II) indicator strips in order to identify the presence of corrosive iron (II) ions. A strong pink color on the strip indicates high iron (II) content in the ink. The majority of pages tested show a strong positive presence of these ions. The inks are then tested to determine their stability in the washing solutions.
Step 2: Removing surface dirt
Surface dirt is removed with grated vinyl eraser crumbs. Removing dirt will prevent the wash water from carrying particulate dirt permanently into the paper's fiber structure during the washing process. Grated erasers are used because they are gentler and clean more evenly compared to solid erasers. The vinyl eraser crumbs are then removed with a hake, a soft Japanese brush.
Step 3: Spraying the paper
Before immersing the paper in an alkaline bath, it is placed on non-woven polyester and humidified by slowly spraying with ethanol and water. Ethanol (grain alcohol) has a low surface tension and functions as a wetting agent, helping the water to penetrate evenly throughout the paper structure. The paper is then sprayed with deionized water immediately after spraying with ethanol.
Step 4: Washing the paper
The humidified document is placed in a bath of deionized water with calcium carbonate added as an alkali. Calcium neutralizes soluble acids and helps to protect and stabilize the iron-gall ink. Ethanol is also added to the bath to ensure even water absorption, to dilute the water, and to aid in even dispersion of soluble iron (II) ions. The discoloration removed from the paper is evident when the bath tray is tilted.
Step 5: Testing the inks again
After washing, the ink is tested again to determine if corrosive iron (II) ions remain. A white test strip indicates a low percentage of iron (II) ions.
Step 6: Sizing the paper
The papers were originally sized with gelatin during the paper-making process in order to create a hard surface. This sizing also helped to protect paper fibers and created a harder writing surface that prevented the ink from feathering. After washing, the dilute gelatin solution is sprayed onto the papers in order to replace sizing that has degraded or been lost during treatment. The gelatin also helps to stabilize the iron-gall ink.
Step 7: Piecing together the fragments
After sizing, the original locations of fragments are determined.
Step 8: Mending the paper
Fragments are attached, and tears are mended using a thin Japanese tissue and diluted wheat starch paste.
Step 9: Flattening the mended pages
After mending, the pages are humidified and flattened by placing them between blotters in the press. The paper is humidified in a controlled moisture chamber. Moisture is sent into the chamber through a tube connected to an ultrasonic humidifier. The temperature and humidity are monitored inside the chamber with a humidistat.