Many genealogists scan old photographs, touch them up in a photo editing program, and then print them on high quality ink-jet printers. There is but one problem: those printed pictures may disappear within a few years.
In testing, pictures printed on Epson's Stylus Photo 870 and 1270 dye-based printers were expected to last ten years. When the products went to market, users found that the colors in prints were changing drastically in as little as two months.
The Hewlett-Packard Photosmart 475, a dye printer that produces snapshot-size photos, will produce photographs that are estimated to last 82 years. No ink-jet printer will create "permanent" pictures.
You can read more about this in an article in the New York Times at http://www.nytimes.com/2007/06/05/technology/circuits/05print.html?_r=1&ref=circuits&oref=slogin.
NOTE: The New York Times frequently leaves articles online only for a few days and then removes them. This article was online when these words were written but may disappear at any time.
A much more technical report is available on the Wilhelm Imaging Research web site at http://wilhelm-research.com.