"A new type of rewritable paper that uses water as ink could slash the amount of paper that's wasted daily, researchers say. The paper contains hydrochromic dyes — chemicals that change color when wet — and a single page can be reused dozens of times, the scientists report in Nature Communications. Other types of rewritable papers have been developed, but they are all more expensive and energy-intensive to produce, and some versions use inks that pose environmental and safety hazards. The new system costs less than 1 percent of standard inkjet printing, the researchers estimate, primarily because ink cartridges are expensive. The researchers found they could refill standard ink cartridges with water and use them, along with the rewritable paper, in typical desktop printers. Print on the rewritable paper is only visible for about 22 hours, or as long as it takes the paper to dry completely. The scientists note that, while 90 percent of business information is retained on paper, most printed documents are read only once before being discarded."

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"A side-by-side comparison of documents printed on the rewritable paper with water ink (a) and on conventional paper with standard ink (b). (Image credit: Sheng, et al., Nature Communications)"

http://e360.yale.edu/digest/rewritable_paper_and_water_ink_could_cut_paper_waste_scientists_report/4083/