There were two reasons to choose cotton paper. One was technical. The other one had to do with how a piece of paper feels in your hand fifty years from now.
The technical reason is simple. Cotton fibres are long. The paper made from them is denser, more dimensionally stable, and resistant to the things that destroy ordinary paper over time. Light. Humidity. The acids in pulp paper that yellow it from the inside out.
What changes after twenty years
Most paper today is made from wood pulp. It is cheap, abundant, and engineered for a specific moment in time. It is also chemically unstable. Acids that come from the wood and from the bleaching process slowly attack the fibres themselves. The page yellows. It cracks at the edges. Twenty or thirty years later it is brittle.
Cotton paper does not do this. The fibres remain stable. The whiteness stays. The bookmark you tuck into a novel today, in 2026, can still be sitting in that same novel in 2076, looking exactly the same.
Why Hahnemühle
There are several manufacturers of fine art cotton paper. Hahnemühle was the obvious choice for one reason: they have been doing this since 1584. Four centuries in the same valley in Lower Saxony, refining the same craft.
Their Photo Rag is one of the most widely used museum-grade fine art papers in the world. It is what the Tate, the Met, the V&A specify when they print a limited edition. It is what Andreas Gursky prints on. There was no reason to use anything else.