How Cremation Works

October 15, 2015

This will be my longest blog post yet....so please bare with me. If you can make it to the end, I assure you that you will know everything you have ever wanted (or not wanted) to know about Cremation

 

How do you want your body to spend eternity? In space, mingling with the stars? Or perhaps as part of a sparkling diamond on someone's finger? Or, if you're looking for something more lively, maybe even nestled among colorful underwater creatures as an artificial coral reef bank? These are just a few of the things people are doing with the cremated remains of their loved ones.

Though people might picture a majestic, flaming Viking ship or a roaring, open-air funeral pyre when talking about cremation, modern-day cremations are much more likely to occur at crematories with industrial machines that efficiently incinerate human bodies.

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.

Though it's gone in and out of fashion since prehistoric times, in the last couple centuries, the rates of cremation have picked up as cultural taboos begin to fall away and modern pressures shape funerary needs.

Some people turn to cremation over burial or entombment because of the convenience, finding it more practical or cheaper to handle ashes instead of a body. Others might be squeamish about the idea of decay and are attracted to the "sanitizing" effect of flames, while some people find it fitting with their spiritual beliefs. Whatever the reason, more and more people are choosing cremation.

In this article, we'll see what happens during a cremation, delve into the history of cremation, find out who's cremating and who's not, and dispel some myths about what happens when human bodies meet fire

 

Cremating a Human Body: Getting Down to the Nitty Gritty

 

The term "ashes" is a bit misleading, since what families receive after a cremation isn't a soft powder, but instead a grayish, coarse material, like fine gravel, made from the ground-up remains of bones.

In modern crematories, the body is stored in a cool, temperature-controlled room until it's approved for cremation. A coroner or medical examiner is often required to sign off to make sure no medical investigations or examinations need to be done since, unlike after a burial, the body can't be exhumed once it's cremated. The body is prepared by removingpacemakers, 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.

Sometimes family members can watch the cremation from a window, or, in cases such as Hindu cremations, a family member can "start" the fire by pressing a button.

Once the door is sealed, the body is subjected to a jet-enginelike 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 [source: Pope].

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 [source: Ellenberg]. A newborn, which has mostly cartilage and very little set bone, might not even leave any remains after cremation.

 

The Cremation Process

The cremation chamber, which is just big enough to accommodate one body at a time, looks a bit like the inside of a pizza oven and can reach temperatures of 2,000 degrees Fahrenheit (1093 degrees Celsius). It's lined with a heavy duty, high density fiber brick designed to retain heat. Those bricks eventually wear out with repeated expansion and contraction and are replaced once they are worn down to about half their original thickness [source: Schaal].

Industrial cremators can run anywhere from $80,000 for a basic, entry-level model to $250,000 for the latest models [source: Sullivan]. The modern-day incinerators are usually automated or computerized and can be programmed to adjust the temperature as needed. They burn natural gas, propane or diesel instead of the coke and coal that fueled retorts as late as the 1960s, allowing for more efficient and hotter burning while leaving little odor or smoke.

During the burning process, a second column of flame is fired up in a secondary chamber to burn off any particles or dust in the air leaving the retort, in order to reduce emissions, smoke and odors. Some retorts also have a wet scrubber in the emissions stack that sprays a mist of water so that escaping particles become trapped [source: Sullivan].

Once the body is completely burned, the cha