Mr Mahdavi says his technique could control the size and positioning of the bubbles in such foam, and so determine the material's strength and rigidity.

ECONOMIST: MONITOR

Talk of bubbles popping in economies the size of China makes investors nervous.

FORBES: No Meltdown As China Banks 'Healthy', IMF Says

Once over the top of a high dune, you come to a hot spring, the size of a large jacuzzi, where sulphurous water bubbles in a pool and runs off to irrigate a garden.

BBC: Siwa: An Egyptian oasis

So we opted for a sombre burial in the Greenhouse, under the shade of the tallest of the mangroves, though in truth it meant a slightly watery grave after all, stuff seeping up through the muck to swallow the foot, bubbles of mud detaching and floating among us during our tiny, foot-size ritual observances.

NEWYORKER: Lostronaut