Chemical Factors – Chemicals used in Production and Preservation of Documents

Chemical factors are important in the production and preservation of documents, as they influence the materials' longevity, durability, and stability. Various chemicals are used in both the creation of documents (such as paper, ink, and adhesives) and their preservation (to prevent deterioration, decay, and degradation over time). Here are key chemicals involved in these processes:

1. Chemicals Used in Document Production

Paper Manufacturing:

Wood Pulp Chemicals: Wood pulp, the base for paper, is treated with chemicals like sodium hydroxide and sodium sulfide in the kraft process to break down lignin and separate fibers.

Bleaching Agents: Chlorine and hydrogen peroxide are used for bleaching wood pulp to produce white paper. Chlorine dioxide is a less harmful alternative in modern practices.

Sizing Agents: These chemicals, such as rosin and alum, are applied to paper to make it resistant to ink and water.

Fillers: Clay, calcium carbonate, and titanium dioxide are added to paper to improve brightness, smoothness, and opacity.

Ink and Dye Production:

Pigments: Organic and inorganic compounds like carbon black (for black ink) or chrome yellow are used for coloring inks.

Solvents: Water is often used in modern inks (water-based inks), but alcohols (e.g., isopropyl alcohol) and petroleum distillates are common in older or oil-based inks.

Binders: Gum arabic, acrylic resins, or synthetic polymers are used to help pigments adhere to paper.

Adhesives:

Starch-based adhesives: Used in bookbinding and some printing applications.

Polyvinyl acetate (PVA): Common in bookbinding and paper repair due to its strong bonding properties.

Animal-based glues: Often used in historical documents, such as hide glue or gelatin.

2. Chemicals in Document Preservation

The preservation of documents involves preventing chemical changes that cause degradation, such as acid hydrolysis, oxidation, and fungal or bacterial growth. Some chemicals used in preservation include:

Alkaline Buffers:

Calcium carbonate or magnesium carbonate is added to paper to buffer acidity, neutralizing acids that can cause degradation.

Alkaline reserve: A small amount of alkaline material is often added to modern papers to prolong their lifespan.

Conservation Solutions:

Sodium bicarbonate (baking soda): Sometimes used in paper cleaning to neutralize acids.

Hydrogen peroxide: Used for cleaning and deacidifying papers, especially in historical document preservation, as it breaks down yellowing caused by oxidation.

Calcium hydroxide (lime): Occasionally used in paper conservation for deacidification.

Mold and Fungus Control:

Ethanol and isopropyl alcohol are commonly used to kill mold or fungi on paper documents.

Copper sulfate and iodine can also be used as biocides to prevent microbial growth.

Stabilizing Agents:

Silica gel and activated charcoal are used in storage environments to control humidity and absorb moisture, reducing the risk of mold or mildew.

Desiccants and humidity control systems: Control moisture levels to prevent water damage or fungal growth.

Fixatives and Coatings:

Acrylic and polyurethane resins are used in conservation to apply protective coatings to fragile documents, stabilizing their surface.

Cellulose nitrate and cellulose acetate have historically been used to coat paper, though their use has decreased due to concerns about their own degradation over time.

3. Preservation Challenges

Acidic Paper: Over time, paper often becomes acidic, either due to the natural aging process or the presence of acids in the paper-making process. This can cause paper to become brittle and deteriorate.

Oxidation: Exposure to air (oxygen) can cause inks, paper, and other materials to oxidize and discolor or weaken.

Pollution: Airborne pollutants, such as sulfur dioxide and nitrogen oxides, can damage paper and inks by creating acidic conditions.

Environmental Factors: Humidity and temperature fluctuations can lead to mold growth, brittleness, and curling of documents.

4. Modern Chemical Treatments

Deacidification Sprays: Several commercial sprays are available that neutralize acids in paper and replace them with alkaline buffers.

Laminating: Involves coating documents with a plastic layer to protect them from physical damage, although this can cause long-term issues if the materials are incompatible.

In conclusion, the chemicals used in the production and preservation of documents play an essential role in ensuring the longevity and functionality of materials. As document preservation practices evolve, a focus on non-toxic, environmentally friendly chemicals is becoming increasingly important.