Pykrete is a super-ice, strengthened tremendously by mixing in wood pulp as it freezes. By freezing a slurry of 14 percent wood pulp, the mechanical strength of ice rockets up to a fairly consistent 70 kg/sq cm. A 7.69 mm rifle bullet, when fired into pure ice, will penetrate to a depth of about 36 cm. Fired into pykrete, it will penetrate less than half as far — about the same distance as a bullet fired into brickwork. Yet you can mold pykrete into blocks from the simplest materials and then plane it, just like wood. And it has tremendous crush resistance: a one-inch column of the stuff will support an automobile. Moreover, it takes much longer to melt than pure ice. But as strong and eco-friendly as it is, pykrete remains forgotten today save among glaciologists, who express bafflement over why no one has made use of it. "I don't really know why it has languished in obscurity," admits Professor Erland Schulson, director of the Ice Research Laboratory at Dartmouth College.2

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2 — Martin Perutz, "Description of the Iceberg Aircraft Carrier and the Bearing of the Mechanical Properties of Frozen Wood Pulp Upon Some Problems of Glacier Flow," in Journal of Glaciology, March 1948, pp. 95-104. There's an entertaining modern experiment involving shooting pykrete at The Schulson quote is from my 7 March 2001 email interview with him.

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