If you're having bad luck with Google, just go directly to Wikipedia instead. Briefly, you'll always follow what billnotgatez: said. to make something porous -- mix it thoroughly with something else, that dissolve/melt away/react away that something else, and you'll have a porous material. This is a common industrial procedure, for everything from porous metals, to porous ceramics to plastic filter material. You want the specifics, but so few people do this at home, you'll have to view corporate sites for any subtle hints they give you, on how its done. As a guess, if you mixed lead particles and organic particles, and applied gentle heat, you might sinter the lead together as you burned away the organic. But what proportions? You'll likely have to determine that experimentally, because its likely a trade secret.