Latex foam in mattresses is generally a blend of the latex of the hevea brasiliensis tree and synthetic latex, which is derived from petrochemicals and other substances and fillers. There are, however, natural latex mattresses that leave out polyurethane-based chemicals. Latex foam is produced using either the talalay or the dunlop process.each provides a different feel. Dunlop is generally a firmer foam, talalay is softer. While the dunlop process produces a denser foam, the talalay process produces a lighter one that has more air in it. If you were to weigh each as latex cores, the dunlop foam would be heavier because it has more latex in it.[citation needed] talalay is more expensive as its production is more resource intensive. Natural latex foam has a higher latex content than synthetic latex, however, "100% natural latex foam" is misleading.