Sell By ...
Just about every food and beverage product you buy has an expiration date. The sell by date is the point of no return, where the perceived quality and safety of the product can not be guaranteed. Often times when this date has passed, the physical and sensory properties of the food change. An odor is present, mold is detected or the food/beverage changes color. As food and beverage consumers, we watch these dates closely and we expect and prepare to replace items as needed. These dates make our lives easier.
The luxury of an expiration date is not available however in printing. When your looking through a paper swatch book, you won't see an expiration date. You will however see key terms that give you an idea of the durability and lifespan that you can expect from the paper. Have you ever noticed when a paper is identified as acid-free or archival? This is the paper's way of providing you with an expiration date.
Acid-free paper eliminates the lignin and active acid pulp (aluminum sulfates) during the processing. Lignin is found in wood and when exposed to light and oxygen, it will cause the paper to turn yellow and deteriorate. The components of paper naturally contain cellulose fibers that produce acid so it is impossible to create an ageless paper. Acid decay can completely breakdown paper over time by deteriorating fibers. However paper made acid-free, will at least slow down the eventual deterioration process.
When an alkaline reserve is added in the paper production process, it will further strengthen the papers ability to fight off naturally occurring acid that forms from the cellulose fibers. This alkaline reserve acts as another protective agent or buffer in the fight against acids. When a paper is alkaline, you can expect an average life expectancy of a few hundred years. Depending on the grade of the paper this can vary from 100-1000 years.
Archival paper is also used to identify paper based on a strict set of standards from ANSI. It means that not only is the paper acid-free with large amounts of alkaline reserves, it is also durable enough to be used for printed items with potential significant historical value to them. Archival paper is considered such because it isn't made from wood-based pulp that contains lignin.
So when you're searching through paper books for your next potential print project and you see that a paper is acid-free and archival, expect it to at least withstand the remainder of your lifetime.