How Cremation Works

Death Image Gallery Funeral director Peter DeLuca, owner of Greenwich Village Funeral Home, holds a cremation urn in the showroom of his funeral parlor in New York City. See more death pictures.
Death Image Gallery Funeral director Peter DeLuca, owner of Greenwich Village Funeral Home, holds a cremation urn in the showroom of his funeral parlor in New York City. See more death pictures.
Chris Hondros/Getty Images

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 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.

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 chamber is then cooled and the cremated remains, which are often still recognizable as human skeletal remains, are swept with a long-handled hoe or wire-bristle broom into a tray. A powerful hand-held magnet is run through the ash to pick up metal parts left behind, such as fillings, plates and hip replacements, which can interfere with the grinding process. The metal parts are disposed with other biological material or recycled [source: Ellenberg]. The bones and remnants are put into a grinder, or cremulator, that uses ball bearings or rotating blades, like a blender. The remains are pulverized and poured into a plastic, lined container or an urn of the family's choice.

If the family requests, the ashes can be mailed via United States Postal Service, which requires a sift-proof box and signed confirmation upon receipt. UPS and FedEx don't ship ashes [source: Harris].

While there may be some inevitable residue mixing, the bodies are burned one at a time to ensure the separation of the cremated remains. Often, a disk identifying the person will be included with the remains throughout the process. Identification papers that travel with the body are placed on the outside of the incinerator and the box of ashes is also tagged and identified to avoid a mix-up.

Next, we'll find out who oversees crematories and some of the scandals that pushed lawmakers to beef up the rules.

Cremation Regulation and Scandal

Crematory operator Joe Bancewicz places a coffin into the retort at Mount Auburn Cemetery, Feb. 21, 2002, in Watertown, Mass.
Crematory operator Joe Bancewicz places a coffin into the retort at Mount Auburn Cemetery, Feb. 21, 2002, in Watertown, Mass.
Darren McCollester/Getty Images

Regulation of cremation and crematories varies from country to country. The U.K. has comprehensive laws on its books dating back to 1902 outlining requirements and restrictions on where and when cremation could take place.

In the United States, regulation often falls under state or local government, and the state laws range from fairly comprehensive to lax with little oversight. The Federal Trade Commission, which regulates the funeral industry, isn't involved with crematories [source: Nicodemus]. Twenty-three of the 50 states license their crematories, according to CANA. Scandals involving crematories in recent years have occasionally pushed state legislators into beefing up these laws.


In early 2002, investigators were astounded by what they found when they looked into an anonymous tip about the Tri-state Crematorium in Noble, Ga.: More than 300 bodies sent for cremation by funeral homes from Georgia, Tennessee and Alabama were instead piled or scattered in various states of decay in the crematorium's vaults, garages and woods.

Tri-state, an independent, unlicensed crematory owned by the Marsh family, had reportedly stopped burning bodies when the incinerator broke down. For years, instead of cremated remains, they had been giving families urns of wood ash and cement.

Strangely, there were no laws on the books against not burning a body, and prosecutors could only charge the operator of the crematorium, Ray Brent Marsh, with fraud and theft for accepting money for services not rendered.

As a result of the scandal, Georgia expanded the definition of corpse mistreatment to include abandonment and disposal. It also closed the loophole that had allowed Tri-state to operate without a license because it didn't serve the public directly. Now all Georgia crematories are required to be inspected and licensed.

A Lake Elsinore, Calif., crematorium owner was accused of selling body parts for medical research -- including heads and torsos -- of the bodies he was paid to cremate. He was sentenced to 20 years in prison after pleading guilty in 2003. Despite the headlines, the donated body parts market for research and education is still largely unregulated.

More recently, in Mississippi, crematory operator Mark Seepe had his license pulled after accusations and evidence of mixing human remains, giving the wrong ashes to the wrong families, and even dumping remains into trash bins. In response, the state legislature passed regulations requiring training for crematory operators and tougher rules for crematories.

What's Left: Disposing of Human Ashes

For families, there is the question of what to do with the ashes. Some keep the cremated remains at home, some choose cemetery buildings called columbariums and others bury the ashes.

Gonzo journalist Hunter S. Thompson went out with a bang when his ashes were mixed with fireworks and shot from a 153-foot (46.6-meter) memorial tower. "Star Trek" creator Gene Roddenberry chose to have his remains shot into space. One company incorporates the carbon from a bit of ash into a synthetic diamond, while other companies mix a teaspoon or two of ash into paint, plaster or other materials that can be turned into works of art. Families can even make their loved one's ashes into a coral reef.


A 2006 survey by the Cremation Association of North America found that out of the cremated remains returned to families, about 38 percent were kept at home, 37 percent buried, 21 percent scattered over water or land and about 3 percent placed in a columbarium. About 1 percent of the cremated remains were never picked up [source: CANA 2006]. Those unclaimed remains present a tricky dilemma for funeral homes and crematories, which are legally allowed to dump the remains after a fixed period of time but often hold on to them for years or even decades, just in case a family member shows up.

Local laws on scattering vary from region to region, and there may be forms or notices to fill out before scattering remains on public land, although many agencies tend to turn a blind eye:

  • The National Park Service leaves the matter up to individual parks, and the National Forest Service doesn't regulate scattering on its lands. Many national parks have prohibited the scattering of ashes except on cemetery lands, and different parks have different requirements for those exceptions. State parks are often more lax but also have their own, individual regulations.
  • For ocean scatterings, the EPA requires it to be done at least 3 miles (4.8 kilometers) away from the shore. In California, people can scatter closer to the shore but still have to be at least 500 feet (152.4 meters) away from the nearest point of land.

One well known, unsanctioned scattering involved the ashes of a die-hard Chicago Cubs fan, Steve Goodman, who passed away of leukemia in 1984. He found his final resting place four years later at Wrigley Field, thanks to a determined friend who snuck in just before opening day and threw Goodman's ashes into the wind toward Waveland Avenue [source: Zorn].

The Choice to Cremate

Although increasing numbers of people are turning to cremation in general, not everyone is so hot to cremate. There is still a wide variety of cultural, religious, economic and regional factors that influence the decision, as shown by a quick look at cremation rates around the world from 2002:

  • Cremation is the dominant form of final disposal in Switzerland (75 percent), Hong Kong (83 percent), the Czech Republic (77 percent), Singapore (77 percent) and the United Kingdom (72 percent). China and the Netherlands cremate about half their dead.
  • Argentina (14 percent), Ireland (6 percent), Italy (7 percent) and South Africa (6 percent) have very low rates of cremation.

[source: Davies]


About 30 percent of deaths in the U.S. were handled through cremation in 2003, compared to only 6 percent in 1975. In the United States, people who choose cremation are more likely to be from the West than the South and are more likely to be white or Protestant than black or Baptist [source: Davies].

A cremation-based funeral can cost thousands of dollars less than a burial funeral, which runs an average of $10,000 [source: Harris]. Funeral directors noted that in a society where people are often transient and move away from their hometown, cremation allows for easier transportation and storage of the remains and lets family members schedule services at a more convenient time.

People are also becoming more aware of the environmental impact of traditional burials, which use an enormous amount of resources, such as rare woods and metals in the casket and cement for a required bunker to line the grave sites, and release toxins from embalmed bodies. The open space used for cemeteries is also a concern for crowded urban areas and countries, such as Japan and Taiwan, where any open space is at a premium.

However, other experts point out that cremations are frequently popular in countries that have plenty of land and open space available, and that funeral homes in America didn't see a jump in cremations during much deeper economic hard times such as the Great Depression [source: Sullivan].

Next, a look at cremation through the ages.

History of Cremation

A woman prays as people gather and pay homage to the late Thai Princess Galyani Vadhana during her cremation ceremony near the royal palace on Nov. 15, 2008 in Bangkok.
A woman prays as people gather and pay homage to the late Thai Princess Galyani Vadhana during her cremation ceremony near the royal palace on Nov. 15, 2008 in Bangkok.
Paula Bronstein/Getty Images

Burning a corpse as a final rite of passage has been in practice since prehistoric times. There is evidence that people cremated bodies in China as early as 8000 B.C. Cremation was commonly adopted in some parts of Greece but never became widespread, disappearing by 480 B.C. In Sweden, the majority of funerals were cremations throughout the Iron Age and Viking Age, but stopped once Christianity was introduced (A.D. 1050). In the western Roman empire, cremation was the standard until the first century A.D., often associated with military honors. With the spread of Christianity, cremation was frowned upon and disappeared for the most part in Europe by the fifth century A.D., except in unusual cases such as epidemics or war.

During the French Revolution, groups such as the Freemasons, revolutionaries and anarchists promoted cremation as a way of reducing the church's role in the funeral process. Partly because of this association, the Roman Catholic Church opposed the use of cremation until the 20th century.


In Asia, cremation became popular in areas of Buddhist influence under certain dynasties in China and Korea until about A.D. 1300. The advent of Neo-Confucianism in the 14th century brought burials back to the forefront in parts of Asia.

Modern cremation began in the late 1800s with the invention of a practical cremation chamber by Professor Brunetti, who presented it at the 1873 Vienna Exposition. Championed by Queen Victoria's surgeon, Sir Henry Thompson, and driven by public concern for hygiene and health and clerical desires to reform burial practices, crematories slowly began opening in Europe and abroad. The first modern crematory in America was established in Pennsylvania in 1876.

Today, cremation is practiced in at least 31 countries around the world, with rates ranging from less than 2 percent in Ghana to more than three-quarters of the deaths in Switzerland [source: Davies].

On the next page, see how different religious views of the human body lead to different attitudes toward cremation.

Religious Views on Cremation

The body of 28-year-old Everest climber and Sherpa guide Karma Gyalzen is cremated May 27, 2003, in Kathmandu, Nepal.
The body of 28-year-old Everest climber and Sherpa guide Karma Gyalzen is cremated May 27, 2003, in Kathmandu, Nepal.
Paula Bronstein/Getty Images

Hinduism is unique among the world's major religions in mandating cremation, called antim-sanskar ("last rite") or antiesthi ("last sacrifice"), as one of the 16 life rituals. Cremation is believed not only to dispose of the body in this life but also to usher the soul into the next world or its rebirth into the next life. Followers of Jainism and Sikhism also strongly prefer cremation, although the doctrines do not strictly require it.

Open-air cremations are practiced regularly in India. In the holy city of Varanasi, bodies are burned atop wood-fueled pyres on the banks of the Ganges River. Varanasi is also home to an electric crematorium that opened in 1989 but has since faced budgetary issues and power shortages.


Christianity, Judaism and Islam all have traditions that frown upon cremation, if not outright prohibit it. Islam instructs its followers to bury their dead as quickly as possible, preferably within the day of the death. (Abhorrence for any practice seen as desecrating a Muslim body also means that there is a shortage of cadavers for medical research in Muslim countries.)

Orthodox and Conservative Jews adamantly oppose cremation on grounds of biblical and Talmudic rulings. Many Liberal and Reform Jews support cremation as an option. However, the history of Nazi cremation of Jews during the Holocaust also influences the opinion of both secular and religious Jews against cremation.

Eastern Orthodox Church prohibits cremation because it as a departure from the belief in resurrection. Mormons, or The Church of Jesus Christ of Latter-day Saints (LDS), strongly support burial over cremation, although the church allows cremation in cultures where it's customary.

The importance and sacrament of the body, as well as the fact that groups that opposed the church advocated cremation, led to the Roman Catholic Church's long-time opposition to cremation, although it wasn't technically against church dogma. In the 1960s, canon law was relaxed and the church reiterated that cremation was allowed without penalty. Requiem Mass can be held with a body that would be cremated or, upon permission of the local bishop, with the cremated remains.

Protestant denominations have historically been more open to the idea of cremation and even advocated for burial reforms at the turn of the century.

While religious views and historical traditions have a strong influence on funerary practices, so do societal, economic and ecological needs. As more people look into cremation as a viable funerary option, they might find it's not as mysterious as they thought.

Lots More Information

Related HowStuffWorks Articles

More Great Links

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