Cremation Process: How Does it Work?

Ever wonder about the steps involved in cremation, the increasingly preferred choice for Americans when it comes to saying final goodbyes? Here we cover the cremation process from the first transport to the last return of the remains.

We’ll cover everything from paperwork to body preparation, flame cremation, pulverization of bones, filling the urn, and final return. You’ll also learn how factors like body weight, age, sex, and physical activity can impact the final weight of the cremated remains.

Whether you’re planning for the future, helping a loved one, or just curious, this article breaks down the cremation process into understandable terms. So, let’s get started.

Cremation process steps:

1. Transport
2. Storage
3. Paperwork (authorization form and death certificate)
4. Preparation of body for cremation
5. Cremation itself
   • Identification check
   • Incineration
   • Separation of materials
   • Pulverization of bones
   • Filling the urn
6. Return of ashes
   

1. Transport

The deceased is moved from the place of death (commonly a home, hospital or hospice) and taken to a funeral home, or sometimes directly to the crematory, also called a crematorium. Crematories contain space for cold storage of bodies waiting to be cremated and also the cremation equipment itself, called a retort. Those moving the body are responsible for carefully confirming the identity at each step. At this stage the body is most commonly placed in a secure bag for moving. In some states, such as New York, a funeral director must be involved. In others families may deal directly with the cremation provider.

2. Storage

The body is placed in cold storage awaiting cremation. The cold stores are more like refrigerators than freezers. The temperature for body storage is between 36 °F and 39 °F (2 °C to 4 °). Bodies can be stored this way for several weeks however it only slows down decomposition. It doesn’t stop it completely. Bodies are stored until paperwork authorizing cremation and any planning for ceremonies are completed.

3. Paperwork (Death Certificate and Authorization Form)

A death certificate will need to be signed off by a doctor, medical examiner or coroner. These professionals also certify that no further examination or judicial inquiry is necessary. Cremation destroys all DNA. In cases of suspicious cause of death, cremation will not be approved because this would destroy evidence.

A valid cremation authorization form must also be completed. Some states permit self authorization prior to death. Otherwise the form is completed by what is known as an authorizing agent. This is usually the surviving spouse, next of kin (e.g. children) or other person who has been legally appointed to be in charge of these affairs. In the case of more than one child, it usually takes a majority of the children to approve cremation.

Some states, such as New York, require a separate cremation permit.

There is usually a mandatory waiting period before cremation can take place following death. In most states 24-48 hours must pass before cremation is allowed. For example, in Texas a cremation cannot take place until at least 48 hours following the time of death indicated on a death certificate unless waived in writing by a local justice of the peace or medical examiner, or a court order. In Illinois, the minimum wait period between death and cremation is 24 hours.

4. Preparation of Body for Cremation

It is not a requirement to embalm a body prior to cremation, particularly if there is no public viewing.

Certain medical device implants such as pacemakers are removed from the body. This is because they contain a chemical (lithium/iodine-PVP) that explodes at high temperatures, making it unsafe for cremation. Radioactive implants (e.g. to treat cancer) must also be removed.

Bodies can be cremated with or without clothing. Most families choose for their loved one to be clothed. Jewelry is usually removed and returned to the family.

Next the body is placed into a rigid cremation container. The container is completely enclosed, leak resistant and combustible. Cremation containers are often made of rigid cardboard, particleboard or pine. More elaborate wooden caskets may also be used as long as they don’t use metal fixtures. Metal caskets cannot be cremated.

5. Cremation Itself

• Identification check – I.D. checks happen at every phase. Just prior to cremation a stainless steel disc with identification information is placed with the body to be with it during cremation. Some families choose to confirm the identity prior to cremation.
• The incineration usually takes around 90 minutes but can be as short as 30 minutes for very small bodies, or over two hours for larger bodies.
  
• Incineration:
  • The cremation chamber is preheated to around 1,100 °F (593 °C).
  • The container with the body inside is placed into the primary cremation chamber, called a retort. The door to the chamber is then closed and the incineration takes place.
  • The temperature for cremation is usually between 1400 °F and 1600 °F (760 °C to 870°C). It involves direct flame, usually generated from natural gas, but can also use propane or butane and sometimes diesel.
  • The incineration usually takes around 90 minutes but can be as short as 30 minutes for very small bodies, or over two hours for larger bodies. The goal is calcination, meaning all water and organic matter is removed, leaving just the inorganic portion of the bones.
    
• Separation of materials – Following incineration the door to the chamber is opened to allow cooling for one or two hours. The bones are then swept out onto a tray with a long handled wire brush or hoe. Any metals that were inside the body are removed by hand and by using a strong magnet. These can be screws, artificial joints, gold teeth etc. In most cases these are collected and sent to a recycling facility.
  
• Pulverization of bones – Once cool enough, the remains are put into another machine to process the bones down into smaller fragments. The machine used to process cremated bones to ash is called a cremulator, or electric cremains processor. It uses spinning blades (similar to a food processor) to break the remains down to be smaller than 1/8th of an inch. The process typically lasts for 30-60 seconds. Older machines used ball bearings and hammers to reduce bone fragments and take longer.
  
• Filling the container or urn – The ashes are then removed from the cremulator and placed into a heavy duty plastic bag, which is put together with the steel identification disc into a temporary container or urn. The cremated ashes usually weigh between four to eight pounds (1.8 to 3.6 kgs). The weight of the ashes depends on the bone weight (size and density), not the amount of fat or muscle as these tissues are burnt away. The process of filling the urn with ashes is sometimes known as inurnment. (Inurnment also refers to placing the urn in its final resting place, e.g. a niche in a columbarium.)
  

6. Return of Ashes

The container or urn containing the cremated remains are held for collection, transferred to the funeral home for collection, or posted to the authorizing agent (the person who signed the cremation authorization form). If agreed, the crematory may take responsibility for the ashes, selecting either a place to bury or scatter them. 

How Long Does the Cremation Process Take: Timeline

The cremation incineration process itself takes 1.5 to 2.5 hours depending on body size. The earliest you can receive the ashes back is 36 hours following death however this doesn’t account for common delays or scheduling with the crematory. Crematories and funeral homes usually give guidance of 2 to 3 weeks as a timeframe to receive ashes back.

• From death to earliest permitted cremation: 24 to 48 hours
• Preparation of the body: varies, 30 mins if no removal of medical devices
• Incineration process in the cremation chamber: 1.5 to 2.5 hours
• Cooling time: 1 to 2 hours
• Processing / pulverizing bone fragments: 60 second cycle, 30 minutes all together

The aquamation process takes longer than flame cremation. Water cremation typically takes around 6-8 hours for higher temperature procedures, or 18-20 hours for machines operating at lower temperatures.

Reasons for Delays in Getting the Ashes Back

• Delays in getting the death certificate signed.
  • In some cases the treating physician is required to sign the death certificate. If that person is unavailable (for example on vacation) there may be delays.
• Delays is getting the authorization for cremation form signed.
  • If there is more than one next of kin there can be delays tracking down everyone to get authorization for cremation.
• Congestion at the crematory.
  • Because cremation rates have been increasing rapidly, supply has not always kept up with demand in all areas and there may be a backlog at the crematory.

Optional Steps in the Cremation Process

• Viewing or visitation
  • A viewing or visitation with the body can take place prior to cremation.
• Funeral service with the body present
  • A full traditional funeral service with open or closed casket can also be arranged before the cremation
• I.D. viewing
  • In some cases the family goes to the crematory to undertake what is called an I.D. viewing. This can bring peace of mind that the body to be cremated is the loved one but should not be necessary.
• Family witnessing
  • Families are permitted to attend the cremation itself in some cases. This can be helpful for grieving and closure. In Hinduism especially, it is tradition for a family member to press the button to initiate the cremation. There will usually be a fee of several hundred dollars for witnessing and some direct cremation providers do not offer this service.
• Memorial service with the ashes present
  • A memorial service arranged by a funeral director, or informally can take place at any time following cremation. It is a good idea to allow sufficient time to be sure that the ashes will be available if this is important.

Differences to Water Cremation / Aquamation

Most of the steps before and after cremation are the same for flame and water based cremation (alkaline hydrolysis). There are some differences in how the body is prepared and what happens to parts of the body not left as remains.

Read more about the alkaline hydrolysis process, including the steps and science behind it.

What Happens to the Body During Cremation?

Almost all soft tissue and a portion of the bones is vaporized during the incineration. The vapor leaves the cremation chamber through a chimney and enters the atmosphere. Prior to entering the atmosphere it passes through a secondary chamber where there is a further incineration. What remains is mainly calcified bone.

Bodies are made up of between 45%-65% water, with elderly towards the lower end. While dead bodies contain less water than living bodies, a good portion turns to steam. 

The temperature of the cremation is 1400 °F and 1600 °F, which is as hot or hotter than a typical wood fire in a home fireplace (which can get up to 1500 °F). However the process is much more efficient and results in a more complete burn.

The process leaves behind small amounts of ash-like remains from tissue and from the casket, if one was used, but the vast majority of remains consists of bones.

What Do Remains Look Like After Being Cremated?

After incineration, but before pulverization, remains look like a collection of broken bones and some granules. It does not look like a skeleton as many bones will be burned up or cracked into pieces. Some larger bones may be recognizable such as the skull, femur and pelvis. The remains are dark to light gray.

What is the weight of the ashes after cremation?

A person’s body weight before death isn’t the main factor influencing the weight of the cremated remains. Instead, it’s the size and density of the person’s bones that make a difference.

Factors impacting the weight of the ashes:

• Height:The ashes of taller people will tend to weigh more than shorter people of the same weight.
  
• Sex: The ashes of males will tend to weigh more than females because males tend to have higher bone density.
  
• Age: bone density decreases in the elderly so the weight of ashes will reduce as we age.
  
• Physical activity: the bodies of people who lift heavy things generally have denser bones so will have more ash.
  

Given this, a general guideline is that cremated remains typically weigh about 3%-5% of the body’s weight. For example, someone who weighed 150 pounds in life would leave behind around 4.5 to 7.5 pounds of cremated remains. For a person who weighed 200 pounds, the remains would typically weigh between 7 to 10 pounds.

In the water cremation, or alkaline hydrolysis, process ashes weigh 20%-30% more than for flame cremation.

Further Questions About the Cremation Process

Does the casket get cremated as well?

Yes, the casket or coffin is cremated together with the body. Clearly if a rental casket has been selected, only the inner container will be cremated.

Do the ashes also include the casket?

Yes, there is a small amount of ashes from the casket itself but the vast majority of the remains are from the bones.

If a wooden casket is used there will be small amounts of ash from the casket itself. Cremation containers made of rigid cardboard will more fully burn.

Where does the metal that remains after cremation go?

Metal remains following cremation are collected and disposed of by the crematory. They may either be sent to medical waste facilities, or metal recycling facilities. In some cases these remains contain valuable metals, for example gold, silver, platinum and palladium. These precious metals are often found in dental work: crowns, fillings and bridges. Other less valuable metals include titanium, zinc, aluminium and copper. These are found in artificial joints and screws. The value of an entire drum can be worth over $13,000.

A typical arrangement is the crematory gathers these materials in a large drum or plastic container. Once fill, they send it to a metal refiner specialising in medical scrap. The refiner then pays the crematory based on the quantity of each metal refined and market prices. In some cases the crematory contributes this money to charity, but not always.

Do they drain the blood before cremation?

No, it is not necessary to drain the blood from a dead body before cremation. Embalming is not required to be cremated. Bodies that have been embalmed will have had their blood drained and replaced with formaldehyde-based chemicals as part of the embalming process.

Can you be cremated with personal items?

Yes a body can be cremated with personal items in some cases. This can depend on the policy of the crematorium but personal items that are fully combustible and do not contain dangerous chemicals can be permitted. For example, photos, flowers, teddy bears should all be permitted. Items made of glass or with batteries will not be allowed.

Some states do not allow personal items or keepsakes to be cremated with the body. For example this is not allowed in New York State.

Do they cremate multiple bodies at once?

No, by most US state laws, and by industry body guidelines only one body can be cremated at once. There are exceptions is if there written authorization from each authorizing agent of the deceased. Practically speaking, cremation chambers are only large enough to hold the body of one adult. Cases where multiple bodies are cremated at once usually involve very early deaths of twins.

For example, here is the rule in Texas regarding simultaneous cremations:

A crematory establishment may not simultaneously cremate the deceased human remains of more than one person in the same cremation chamber unless authorized in writing by the authorizing agent of each deceased person. (Texas Health and Safety Code, Title 8, Sec. 716.153)

Utah’s rules are similar:

Simultaneous cremation of the human remains of more than one person within the same cremation chamber or processor is not allowed, unless the funeral service establishment has received specific written authorization to do so from the authorizing agent of each person to be cremated. (Utah Code, 58-9-610)

Another instance where the cremation of multiple bodies may be permitted is in the case of early miscarriage, or termination. For instance in cases where the hospital has custody of the fetus and where the mother has not chosen other options.

Read here for cremation myths busted