From A Wiki of Ice and Fire
Wildfire is a volatile liquid that can burn for a long time. Once wildfire takes fire, the substance will burn until it is no more. It will seep into cloth, wood, leather, and even steel so that they take fire as well. Wildfire will burn even when floating on water, it is typically commissioned for use as a weapon of war, though Alchemists will sometimes use wildfire torches as a display of power. The red priest, Thoros of Myr, fights with a sword covered in a thin layer of wildfire.
Making wildfire is a lengthy and dangerous process, which is only known to the Alchemists' Guild who claim it involves magic. The alchemists place wildfire in small jars of pottery, the clay roughened and pebbled to improve grip. The jars are filed in a series of bare stone cells. Over each cell lies a room filled with sand and a "spell" on the floor so that should anything happen, the sand will fall on the fire and help extinguish it. Old wildfire is 'fickle', any flame, any spark can set them off. Too much heat - such as that caused by being exposed to sunlight for even a short time - could lead to a fire as well. Once the fire begins, the heat makes the wildfire explode violently which can lead to a vast chain reaction. The more volatile jars of wildfire are transported from place to place only by night, in carts filled with sand to lessen any jostling at all and then sealed in wax and placed in rooms pumped full of water.
Certain steps in making wildfire work better and more efficiently as of more recently. A pyromancer speculates that this could have something to do with the talk of dragons coming back into existence, as an old Wisdom Pollitor held to the idea that the spells for making wildfire were not as effectual as they once were because dragons had gone from the world.
|“||"The substance flows through my veins, and lives in the heart of every pyromancer. We respect its power." ||”|
|“||"Piss on wildfire, and your cock burns off." ||”|
|“||Fifty feet high, a swirling demon of green flame danced upon the river. It had a dozen hands, in each a whip, and whatever they touched bust into fire. ||”|