Cremation is the process of burning a dead body at very high temperatures until there are only brittle, calcified bones left, which are then pulverized into "ashes." These ashes can be kept in an urn, buried, scattered or even incorporated into objects as part of the last rites of death.
The body is prepared by removing pacemakers, which can explode in the heat, prostheses and silicone implants. Radioactive "cancer seeds" -- injectable or implantable radioactive isotopes used to treat several types of cancer -- are also on the removal list. The body is then put into a container or casket made out of flammable materials such as plywood, pine or cardboard. In some countries, workers remove other external items such as jewelry or glasses, while other countries prohibit workers from doing so.
When the incinerator is preheated to about 1,100 degrees Fahrenheit (593 degrees Celsius), the mechanized doors are opened and the container slips quickly from a rack of rolling metal pins into the primary cremating chamber, also referred to as a retort. Once the door is sealed, the body is subjected to a jet-engine-like column of flame, aimed at the torso. The heat ignites the container and dries the body, which is composed of 75 percent water. As the soft tissues begin to tighten, burn and vaporize from the heat, the skin becomes waxy, discolors, blisters and splits. The muscle begins to char, flexing and extending limbs as it tightens. The bones, which are the last to go, become calcified as they are exposed to the heat and begin to flake or crumble.
An average human body takes from two to three hours to burn completely and will produce an average of 3 to 9 pounds (1.4 to 4.1 kilograms) of ash. The amount of ash depends usually on the bone structure of the person and not so much their weight. A newborn, which has mostly cartilage and very little set bone, might not even leave any remains after cremation.
|The straight cut in the skull is from the autopsy.|
|The dark mass behind the skull is the lungs.|
|Still a little tissue left on the skull.|
Images via Imgur