Aluminum foil is produced as a thin sheet of rolled and pressed aluminum generally .0043mm to .15mm. The biggest use of aluminum foil is as a packaging material, especially for food items. It is impermeable to water vapor and gases at one millimeter thick. Thinner gauges can also be impermeable when combined with other laminates. This characteristic makes it the perfect vehicle for food packaging. Aluminum has a high resistance to fats, petroleum grease and organic solvents. Foods such as candies, milk, chips, and butter do well with foil packaging and many have some form of it as a protector. The opacity which blocks light and can help seal in heat is another benefit. This can be seen in the use of thermal blankets, which are thin sheets of foil laminated with a strengthener.