When an ink is called “archival”, it means that the ink has been designed specifically to be resistant to weathering and fading so that it will last for a long time. It is often used to create “museum-quality” prints, usually fine art prints and photographs, but is also occasionally used for printing documents. Ideally, archival ink should be used in conjunction with archival paper, which is also made to resist weathering and fading.
With the passage of time, normal inks will begin to fade, especially with repeated exposure to UV rays. Many black inks will initially turn brown before completely disappearing from the page. Exposure to moisture can also wash out regular ink, leaving it blurry, smeared or completely erased. While chemical components slightly differ from ink to ink, archival inks all contain bigger molecules and elevated alkaline levels.
Dyes and Pigments
These days you are able to find dye inks and pigment inks that call themselves “archival”, and often times it’s a matter of opinion as to what is “archival” and what is not.
Most inks can best be described as dyes. Because the dye is composed of single molecules it lays flatter on the paper surface and reflects light more evenly and appears more vivid. However, the smaller molecular structure of dye-based ink also allows it to be damaged by UV light more rapidly that pigmented inks.
Pigment is a far more reliable component of archival ink. Pigment is insoluble. It consists of much larger molecules than that of dye, therefore the reflection of light received from a pigmented print does not appear as vibrant due to the scattering of the reflected light. The larger molecules allow a pigmented ink to last substantially longer than a dye-based ink. This makes pigments popular for use in archival pens, inks and printer cartridges.
Archival dye inks tend to be cheaper, because their base materials are less expensive. Some of these dyes are quite strong and suitable for the needs of most people; they may last, for example, for several generations. Pigment-based versions will be substantially more expensive, but they also confer a greater sense of permanence. Official government documents, for instance, are often produced with pigmented inks to ensure that they are still readable by future generations.
One note, before you begin using archival ink – archival inks don’t usually work well with glossy paper surfaces. The gloss coating often keeps the dye or pigment from properly adhering to the paper fibers. When using archival ink, it’s best to use archival (acid-free), matte paper.