Traditionally, paper is made from wood, which contains a polymer called lignin. It’s biological function is believed to be to provide strength to a plant as it is positioned between the plants’ cellulose structures in the cell wall and its hydrophobic nature helps with the transport of water. Unfortunately, lignin, as a result of its acidic nature, has a tendency to discolour when exposed to air, thus causing paper to yellow with age.
Lignin can be removed from paper to avoid its degeneration, but a lot of papers used for giclée printing are manufactured from cotton rather than wood, as cotton does not contain lignin.
Another factor to be aware of in choosing the right papers to achieve optimum quality is the use of optical brighteners.
Optical brightening agents (OBAs) are additives used in the paper industry to enhance whitening effects of papers. These chemical compounds absorb light in the UV and Violet regions and re-emit lighten inn the blues region. This produces a fluorescent effect that masks the “yellowness” of the fiber and enhances the brightness of paper.
Although they may initially seem to provide a pleasant tint to the paper, sadly they degrades quite quickly. as with other acidic components, OBAs degrade via oxygenation and will therefore cause paper to yellow over time.
So, good and bad about paper:
Lignin and optical brighteners are harmful to paper. In order to preserve the archival nature of your print, either use cotton-based paper or wood-based paper with its lignin removed and without optical brighteners.