Anyone who owns a printer knows that printer ink is expensive. Water would be much cheaper.

Chinese scientists reporting in the journal Nature Communications say they have made a simple printer that uses water instead of ink. The printed characters last for a day on special paper, which can then be re-used.

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“Every time you print it's fresh,” Sean Zhang, professor of chemistry at Jilin University in Changchun, China told Discovery News in an interview. “We are using a commercially available inkjet printer. We just filled the cartridges with water and put it back. It’s like normal printing. The magic is in the paper.”

Zhang is a former researcher at Hewlett-Packard Labs in Menlo Park, Calif., and is now a professor at the State Key Laboratory of Supramolecular Structure and Materials at Jilin.

He said that printing typically involves large amounts of waste paper and expensive ink to prepare documents often read only once. This method allows the paper to be reused numerous times and could potentially have cheaper associated running costs.

Zhang and his colleagues developed a special coating on the paper that responds to the water. So far, they have been able to print various Chinese and English characters using blue, magenta, gold and purple colors, using water as a key that activates the dye molecule. The next step is to combine colors to get black, Zhang said.

The possibility of reusing paper instead of throwing it away is intriguing, according to Kira Barton, professor of mechanical engineering at the University of Michigan and an expert in high-performance printing technology.

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“Going toward more sustainable techniques of printing is helpful and beneficial,” Barton said. “It would be interesting to quantify the quality and regularity and repeatability you could get before you see degradation. For standard typing, I think it’s an interesting idea and something worth exploring.”

Zhang said that he foresees advances in printing technology that would allow consumers to have entire newspapers or magazines printed at home with paper that could be recycled over and over again. Based on 10 uses per sheet of water-jet paper, Zhang estimates the cost at one-seventeenth the current price of inkjet printing.

That may not be cheap enough, according to one expert, since regular single-use paper is so cheap.

"Technology for using hydrochromic dyes to make rewritable paper is exciting as a new approach for avoiding the problem of single-use paper," said Norman Marsolan, director of the Institute for Paper Science and Technology at the Georgia Institute of Technology, in an e-mail. "Because existing paper products are inexpensive, however, this new technology will have to be cost-competitive, even if it can be rewritten many times."