Whether you’re considering cremation for yourself, a loved one, or just curious, it’s normal to wonder, “how does cremation work?”
We’ll explain the process from start to finish.
Also, we’ll answer some of the most common questions people have about cremation, including some you probably never thought to ask.
Topics Covered In This Article
Cremation uses extremely high heat and flames to burn a deceased person’s body until nothing is left but bone fragments.
This process is also known as flame-based or traditional cremation. It’s the most common type of cremation.
Some people also call it a cremation retort, a cremation chamber (or even an “oven,” if they don’t know the technical terms).
The chamber is lined with special materials that help it retain heat to make the burning process more efficient.
There’s another type of cremation that people call water cremation, water-based cremation, aquamation, or flameless cremation.
The scientific term is alkaline hydrolysis.
Alkaline hydrolysis takes place inside a completely different type of chamber that is air and watertight.
It can be a more environmentally friendly option, so you might hear it called bio cremation or green cremation.
Like flame cremation, water cremation also rapidly breaks down the human body until only bone fragments are left.
After the burning is complete, the cremated remains need time to cool off before they can be handled safely.
There won’t be any coffin or casket left. The heat destroys everything except bone and metal.
Metal remains can include items such as:
- Artificial hips, knees, and shoulders
- Medical pins
- Titanium spinal rods
- Metal watch bands
- Surgical clips
- Medical staples
A technician will use a heavy-duty magnet to remove any metal from the cremated remains.
The crematory will send any metals for recycling or donation.
Next, the technician gently rakes or brushes the cremated remains into a pan.
With metal pieces removed, what remains of the body after cremation are bone fragments (calcium and phosphate).
Some components, such as part of a skull or femur, can be pretty large.
And at the end of each type of cremation, a machine called a cremulator (or processor) pulverizes the bone fragments into fine dust.
That dust is what they place into the urn.
Contrary to popular belief, the “ashes” in an urn aren’t actually ashes. They are just finely crushed bone fragments.
Ashes are just a euphemism, a more pleasant term for the remains.
Depending on the processing equipment and the person running it, the cremated remains may have a different final consistency that may be finer or coarser.
Often, they are gritty and have small pieces in them.
Finally, the cremation technician carefully packages the processed remains into a plastic bag.
The bag will also include the metal identification tag or disc that has been with the body throughout the process.
The bag is then placed inside a temporary plastic container or “utility urn” if the family hasn’t yet picked out a decorative urn.
If the family requests it, the remains may be divided into more than one urn so several loved ones can each have their own remembrance.
|Flame Cremation||Water Cremation|
|Cause of decomposition||Flames and extremely high heat||Chemicals, liquid, and low heat|
|Cremation temperature||1,400 to 1,800 degrees Fahrenheit||199 to 302 degrees Fahrenheit|
|End result for loved ones||Pulverized bone fragments placed in an urn||Pulverized bone fragments placed in an urn (typically one-third more compared to flame based cremation|
|Preparation||Certain medical devices and implants must be removed||Certain medical devices and implants may remain in the body (varies by state law)|
|Cremation time||90 minutes to 4 hours||3 to 16 hours|
|Direct cremation average cost||$2,183||$1,500 and up|
|Availability/legality||All 50 states||Limited providers in select states|
|Environmental impact||Potentially worse||Potentially better|
Most of the details in the rest of this article refer to traditional flame cremation unless otherwise noted.
It’s far more available throughout the United States than water cremation.
The crematory operator will place the body onto a cart or hydraulic lift table when the body arrives at the cremation facility.
The operator will record the person’s weight and gender (sometimes).
They’ll also register the name of the funeral director and the start and end times of the cremation process.
If the body is clothed upon arrival, the clothing will typically remain.
The body will be placed into a sturdy coffin-like container that is combustible.
Wood cremation caskets typically consist of inexpensive materials such as woodgrain laminate, pine, or plywood.
The crematory operator must remove anything that could cause problems during the cremation process.
Because of the high heat, the batteries in pacemakers and implantable cardioverter defibrillators (ICDs) can explode during or after cremation.
That could damage equipment and potentially harm or kill the crematory operator.
Other medical devices, such as pain pumps and spinal cord stimulators, must be removed for the same reason.
Metal implants, such as artificial hip joints, need not be removed.
However, cancer-fighting implants, sometimes called cancer seeds, often need to be vacated.
They must also remove prosthetic limbs or silicone implants used in cosmetic and reconstructive surgery.
When those materials melt, they damage the cremation bricks (also called refractory bricks) that help the retort stay hot.
In addition, the funeral director will remove any valuable or meaningful jewelry beforehand at the family’s request.
If you die at home in the company of a relative, close friend, or caretaker, someone who was present will contact a funeral home or crematory to arrange for the pickup of your body.
If you die unattended (alone), especially if you’re not at home or the cause of death is suspicious, the person who finds you should call a coroner or medical examiner.
A professional would come to the scene to identify the body, determine the cause and manner of death, transfer the body to a storage facility, and contact the next of kin.
With the coroner or medical examiner’s approval, the body can go to a funeral home or crematory.
Just keep in mind that the process could be different depending on the location. Federal, state, and local laws govern the transportation of a deceased body.
But remember that cremation costs vary by provider and region.
And you can choose to spend less than the average.
If you’re concerned about the cost, check out our guide to finding the best cremation insurance.
The least expensive option is direct cremation (aka “immediate cremation”), which includes no funeral services. The average cost of direct cremation is $2,183.
Here are the services that comprise the total cost of a direct cremation:
- Transporting the body to the funeral home
- Collecting the necessary information and completing the required paperwork to authorize the cremation
- Keeping the body in cold storage between death and cremation
- Filing the death certificate
- Performing the cremation
- Placing the ashes in a temporary urn
- Ordering official copies of the death certificate
- A wooden rather than fiberboard casket
- Expedited service
- A viewing of your loved one
- Writing an obituary
- Running an obituary
- Holding a memorial service
- Printing programs for the memorial service
Cremating people of size
A morbidly obese or bariatric individual typically costs more to cremate.
The process takes longer because burning large amounts of fat creates flare-ups, similar to burning gasoline, requiring extra-careful supervision of the cremation process.
Heavier people burn hotter, so crematory operators typically cremate bodies from heaviest to lightest in a given day to reduce the risk of the retort overheating.
It takes more staffing and planning to cremate an individual larger than 300-350 pounds.
Also, it may be necessary to shut down the retort during the process to prevent the machine from overheating.
Witnessing the cremation process is another factor that can increase a family’s cost to cremate a loved one.
If someone wants to watch the cremation process, the crematory may need to shut down its other operations for the day.
They cannot cremate other bodies, which translates to lost income.
In addition, the facility may need additional staff to work with the family during the process.
A witness cremation outside of regular business hours may cost even more.
Cremation price transparency
Any death care facility you contact, be it a funeral home or a crematory, must be transparent about their prices.
The Federal Trade Commission’s funeral rule requires these businesses to give anyone a price list upon request. You have a right to this information under federal law.
Some places even publish their prices right on their websites.
Try our calculator to estimate funeral costs for yourself or a loved one.
Cremation has steadily grown more popular in the United States over the last 15 years, according to data from the Cremation Association of North America (CANA).
In 2021, more than half of deaths—57.5%—resulted in cremation, compared to 56.0% in 2020 and 54.4% in 2019.
But as recently as 2006, just 21.8% of U.S. deaths resulted in cremation.
Funerals, religion, and cost
One reason cremation may be gaining popularity is that people’s funeral and burial preferences have changed.
Americans have become less interested in holding funerals, especially public funerals.
They are also becoming less interested in burials.
Direct cremation, which no funeral or memorial service, has become more common.
So have private at-home funeral services or celebration of life services limited to family and possibly close friends.
Further, Americans have become less religious, making religious funerals less common.
Also, organized religion has become more accepting of cremation. (Some religions still consider it harmful to the soul, however.)
Cremation has also become more socially acceptable.
Another reason cremation has become more common is cost.
Cremation, especially direct cremation, is far less expensive than a traditional funeral and burial.
Average funeral costs for a burial service come close to $10,000.
It’s hard to talk about cremation these days without mentioning its environmental impact.
However, flame cremation may not be as bad for the environment as you think, at least in the United States.
According to CANA, one cremation, on average, uses the same amount of energy as 20 gallons of gas.
That’s the same amount of gasoline people use while driving for a week or two.
The truth is, the environmental impact of one person’s cremation depends on a multitude of factors:
- Equipment the crematory uses
- How well the cremation equipment is maintained
- The type of container the body is placed in (plastic body bag, fiberboard, varnished wood)
- Amount of adipose tissue (fat) on the body
- Materials that burn with the body (clothing, glasses, dental fillings, implants)
- Person’s age at the time of death
Greenwashing in the death care industry
Aquamation can be a greener alternative, but reducing the environmental impact of dealing with human remains isn’t as simple as choosing one method over another.
For example, transporting a body hundreds of miles for a green cremation likely won’t be better for the environment than flame cremation.
With so many factors to consider, it’s essential to look beyond the marketing, which is sometimes just greenwashing.
Different types of materials create different kinds of emissions when they burn.
Cardboard burns differently than wood; different types of wood burn differently.
Old metal fillings in teeth can release mercury into the air; plastics can release harmful gasses.
In countries with looser environmental regulations, cremation can negatively impact the environment.
One example is India.
The smoke from so many open-air funeral pyre cremations during the Covid-19 pandemic may have decreased air quality so much as to cause additional deaths from respiratory problems caused or made worse by the air pollution.
The United States only has one open-air funeral pyre available to the public.
It’s at the Crestone End-of-Life Project in Colorado. It’s only allowed to perform 12 cremations per year.
It is illegal for the crematory to leave recognizable bones at the end of the process. Also, most of the material is relatively brittle. Even if you wanted to take home your grandmother’s skull and it was legal, it would be more fragile and less whole than you were probably hoping.
The crematory issues a metal tag or medallion to that individual that is typically placed inside the coffin with the body. It’s sometimes placed outside the retort during the cremation process to help keep track of that person’s identity.
The metal tag does not burn and is one of many safeguards to ensure that the crematory can correctly identify cremated remains. It has a unique identification number for each person, along with the name of the crematory. It’s attached to the plastic bag containing the cremated remains.
Flame cremation typically takes one and a half to four hours, depending on the size and composition of the body and the type of coffin. It also depends on whether it’s the first or last cremation of the day, which parts of the process you include in the time calculation, and which cremation expert you ask.
Yes, the coffin is cremated with the body. Once the coffin is safely inside, the door closes, and the burning process begins.