See link to an interesting site discussing Archival and Longevity Qualities of Eco Materials in Art

For archival longevity in artwork, 100% cotton or cotton and linen rag paper are the preferred choices. These materials are known for being acid-free, lignin-free, and durable, ensuring the artwork resists yellowing, fading, and deterioration over time.Here’s why these fibers are so good for archival purposes:

Durable Fibers:

Cotton and linen have long, strong fibers, making them more resistant to degradation than wood pulp-based papers. 

pH Balanced:

Archival paper is typically pH balanced, further enhancing its longevity. 

Resistant to Yellowing and Fading:

These properties help to ensure the artwork retains its original vibrancy and appearance over time. 

Suitable for various art media:

These papers can be used for a wide range of art media, including oil painting, watercolors, and more. 

Acid-free materials:

When storing or framing artwork, use acid-free materials like mat boards and adhesives to avoid further damage. 

UV protection:

If displaying artwork, use UV-resistant glass to help prevent colors from fading