Paper is an indispensable part of our daily lives. From newspapers to books to bills, we use paper extensively. Over time, paper may lose its brightness and turn yellow. Have you ever wondered why this happens? In this article, we will explore the science behind discoloration of paper.
The Structure of Paper
Paper is made up of plant fibers, mostly from wood pulp. These fibers are held together by a matrix of lignin and other compounds. Lignin is a complex organic polymer that provides rigidity and strength to the cell walls of plants. In paper, lignin acts as a natural glue that holds the fibers together. However, lignin is also responsible for the yellowing of paper.
The Chemistry behind Paper Yellowing
Paper is susceptible to discoloration due to various chemical reactions. The most common cause of paper yellowing is oxidation. Oxygen molecules in the air react with lignin and other organic compounds in the paper, causing them to degrade and turn yellow. This process is accelerated by light and heat, which break down the chemical bonds in the paper and accelerate the oxidation process.
Another cause of paper yellowing is exposure to acidic conditions. Acidic substances such as pollution, acids from framing materials, and even natural byproducts from the paper itself can cause paper to yellow over time. Paper produced before the mid-19th century was often subjected to acidic conditions, which is why many ancient documents and books have yellowed pages.
Preventing Paper Yellowing
If you want to preserve the brightness and color of paper, there are some steps you can take to prevent yellowing:
- Store paper in a cool, dry place away from direct sunlight and heat sources.
- Use acid-free paper and framing materials.
- Avoid touching paper with bare hands as oils and dirt from the skin can cause discoloration over time.
If you have paper that has already yellowed, deacidification may be an option. This process involves removing the acidic compounds from the paper and replacing them with an alkaline compound. You can find deacidification sprays and solutions at art supply stores, but it is best to seek professional help to avoid damaging the paper.
Yellowing of paper is a natural process that occurs over time due to various chemical reactions. By understanding the science behind discoloration, we can take steps to prevent it and preserve the color and brightness of our paper.
Q: How long does it take for paper to turn yellow?
A: The time it takes for paper to yellow depends on various factors such as the type of paper, exposure to light and heat, and humidity levels. It may take a few years or several decades for paper to turn yellow.
Q: Can I reverse paper yellowing?
A: It is possible to deacidify paper to reduce or reverse yellowing. However, the success of this process depends on the severity of discoloration and the type of paper. It is best to seek professional help for valuable or delicate items.
Q: Does all paper turn yellow?
A: No, not all paper turns yellow. Factors such as the quality of the paper, the environment it is kept in, and how it is handled determine if and how quickly paper will degrade and discolor.
Q: Can I use bleach to whiten yellowed paper?
A: No, using bleach or other harsh chemicals on paper can cause permanent damage and may even accelerate the discoloration process. It is best to consult a professional conservator for the proper treatment of damaged or discolored paper.