Cremation is a common practice in many cultures, but have you ever wondered what cremation ashes really are? Cremation ashes are the crushed pieces of bones and teeth that are left over after the cremation process. During cremation temperatures rise to between 400 °F and 1600 °F (760 °C to 870°C) from direct flame. The cremation process burns away the soft, organic parts of the body, leaving only the hard, inorganic parts of bones and teeth.
But sometimes you get back more than just bits of bone. Read on to learn more about ashes and see what else may be included when you get them back after cremation.
Key Points:
- Cremation ashes are not really “ashes”, they are ground up bones
- The main part of the bones remaining is calcium phosphate, which is the inorganic part that is left after everything else has been burned off
- Sometimes bits of other items can also be included, e.g. surgical staples and parts of dental work
Table of Contents
What are Cremains?
“Cremains” is an industry word that refers to the cremated remains of the body. It is a mix, or “portmanteau” of the words “cremation” and “remains”. Cremains are otherwise known as “ashes”.
What are Cremation Ashes Made of?
Cremation ashes are made from the pulverized inorganic remains of bones fragments and teeth following incineration of the body. These parts are mainly made from calcium phosphate.
Organic parts of the body include anything fleshy, such as skin, muscle, fat, organs and bone marrow. Organic parts contain carbon. These parts are almost all vaporized, with trace amounts of ash from organic matter remaining. It is these trace amounts of carbon that are used to create cremation diamonds.
To understand what cremation ashes are made of, it’s helpful to first understand the composition of bones and teeth.
The Chemistry of Bones and Teeth
Bones consist of about 60% inorganic minerals, 30% organic materials and 10% water. The organic parts of bones are mainly the bone marrow which is made from collagen. The inorganic part of bones are made from a type of calcium phosphate and is known as “bone apatite.” The process of reducing the bone to its inorganic part is known as “calcination”.
Teeth are made from three different tissues: enamel, dentin and cementum which are also made up of organic and inorganic material. Enamel is the hardest part of our bodies and is about 96% inorganic. Dentin is about 70% inorganic and cementum is about 50/50 organic and inorganic.
The major components of the calcium phosphate bone minerals are: calcium, phosphorus and oxygen. The minor components are sodium, magnesium, sulfur, fluorine, chlorine and potassium. Prior to cremation the original bone mineral is a carbonated apatite and during cremation it reacts and reforms to become hydroxyapatite. Another mineral also forms called buchwaldite (NaCaPO4) which is another kind of calcium phosphate.
Because of the thickness of some bones, like the femur, it is hard to completely burn away all organic compounds and there is usually a small portion of carbonates left inside thicker bones.
What do Cremation Ashes Look Like?
Cremation ashes look like coarse grains of sand or fine gravel and can vary in color but are mostly grayish. There are not like ash from wood fires. Human ashes typically weigh around 4.0 to 7.5 pounds although the weight can vary significantly. The average sized ashes usually fit into a standard 200 cubic inch cremation urn.
What Color are Cremation Ashes?
Cremated ashes are usually grayish, with some lighter and some darker colors. Darker colors indicate that they have not been fully combusted and some carbon still remains. Ashes can also have tints of color such as pink or green which comes from minerals absorbed during life such as copper.
Ashes that come from alkaline hydrolysis, or water cremation, are white and weigh 20% to 30% more than ashes from flame cremation.
What Happens to Bones During the Cremation Process?
Organic Matter and Water is Burnt Away
As mentioned above, bones contain about 30% organic matter and 10% water, mostly in the bone marrow as collagen. These parts are vaporized, leaving behind the inorganic structural parts of the bone. Carbon within the bones is oxidized and turns to carbon dioxide.
The Color of Bones Changes During Cremation
As the cremation chamber heats up the bones, their color changes from cream to brown to black to gray to white. This happens due to the oxidation of organic carbon under flame. The black stage is due to organic materials breaking down into raw carbon. The carbon is completely combusted at 800 C and bone turns to white in color.
Cremated Bones Can Turn Pink or Green
Sometimes cremated bones, and the ash made from them, can turn pink or green. This is due to the minerals absorbed during the person’s lifetime. The pink color in cremated bones and ash comes from the mineral copper.
Bones Crack and Break Apart
As bones lose moisture and collagen they crystallize, become brittle and form cracks. Smaller bones can fall apart completely and only larger bones retain their shape and are still recognizable, such as the femur and pelvis.
Bones Shrink
Bones shrink by about 15% during cremation. They get smaller as around 30% of their organic and water components are burnt away.
Bones are Pulverized by Machine Following Incineration
Once the bones have been incinerated, they are left to cool. A cremationist then sorts the bones by hand, removing any foreign objects like medical devices. A magnet is also used to remove metal items. The bones are then put in a machine called a cremulator to be processed down to granules. The machine acts like a food processor and takes around 60 seconds. More about the full cremation process.
Are Cremation Ashes Real Ashes?
Ashes are the solid remnants of fires. In this respect, cremation ashes are real ashes. However, immediately following incineration bodies don’t turn to what we would recognize as ash. After incinerating a body, what is left behind is bones, which are then ground up to become “ash”.
When most of us think of ashes we think of wood ash, the solid remnants after a fire. The ashes after a wood fire usually contain materials that are combustible, they just haven’t fully burnt away. The darker the wood ash the higher amount of combustible material. Ashes from cremation have a very different texture to wood ash.
Are Water Cremation Ashes Real Ashes?
Water cremation ashes are not technically real ashes because by definition ashes are the solid parts of what is left after a fire. However, the end result of both flame cremation and alkaline hydrolysis is similar: both processes leave behind the inorganic parts of the bones. The water cremation industry does sometimes refer to the remains as ashes.
What Else Can Be In Cremation Ashes?
Apart from teeth and bone, there can be other items mixed in with the ashes. These are items that are not combustible (so they are not incinerated during cremation) and that have accidentally slipped through detection. Following the incineration, a cremationist sorts through the remains to remove items that are not of the body. They sort by hand and also by using a magnet to remove metal objects. Sometimes items are missed and they can end up in the remains.
Foreign items mixed in with the ashes can be from several groups. These will sometimes be in parts if they have been crushed up during the processing of the bones.
Surgical Items
Larger medical objects like artificial joints are easy to spot and remove however smaller things can be difficult to detect. Pacemakers are removed before cremation but most other implants are not. Examples of medical objects which have been found mixed in with ashes include: surgical staples, small screws, wires and leads from medical devices.
Dental Items
Parts of bridgework, porcelain crowns, veneers, amalgam fillings can sometimes escape detection and end up mixed in with cremation ashes. Most should have been removed but not all items are easily visible or magnetic. For example, fillings are usually made up of 50% mercury, plus silver, tin, copper and other metals which together are not picked up by magnets. If the body has been embalmed, there may be pieces of needle that have been used to keep the mouth from opening.
Personal Items
Small objects from clothing, or other keepsakes that were cremated can leave behind traces which end up in ashes. For example, bra clasps, parts of zippers, metal ties used with flowers, parts of jewelry or staples from books have all been found in ashes.
Parts of the Casket, Coffin or Container
Cremation caskets and containers are mostly made from combustible materials like wood or cardboard which do not leave significant traces behind. However some use small metal staples at the joins which will survive cremation. These can pass detection and end up in cremation ashes.
Traces of the Ashes from Other People
Cremation chambers are thoroughly swept out between uses with a long handled wire broom or hoe. However, it is impossible to clean every inch 100% and it is likely that there are trace amounts of ashes or even very small medical or dental items from previous cremations that are included in your ashes. Unless they are non-bone objects you won’t be able to tell the difference. Cases of mixed ashes are rare but can happen.
Other Questions About Cremation Ashes
Where do they put bones after cremation?
After cremation bones are ground into a fine powder using a machine that acts like a food processor. The powder or “ashes” are then put into a sturdy plastic bag and sealed. The bag is then placed into a cremation container which can be made of plastic or cardboard or directly into an urn.
Are Cremation Ashes Toxic?
Cremation ashes do not contain any pathogens that could cause you to get sick. They are mainly made up of calcium phosphate. In a different forms calcium phosphate is used as a supplement and in fertilizer. Ingesting a little bit of ashes is unlikely to cause illness but should be avoided.
Does Cremation Burn Everything?
No, the inorganic parts of bones and teeth do not burn during cremation. Almost all organic parts of the body will be burned and vaporized but there will be very small amounts left.
Do Bones Burn During Cremation?
About 40% of bones are burnt during cremation, leaving behind about 60% of the original weight. Water and organic parts of bones like bone marrow are burnt away during cremation, leaving behind the inorganic structural parts of bones. The bones shrink by about 15%.
Why Don’t Bones Burn During Cremation?
The inorganic parts of bones are made of hard minerals which are not combustible. These parts are made from calcium phosphate and like tooth enamel, do not burn during cremation.
Do they Break Your Bones Before Cremation?
No, bones are not broken before cremation. Bones do break during cremation as they dry out and become brittle. After cremation they are broken into little pieces in a machine to become what we know as “ash”.
Does the head explode during cremation?
No, the head doesn’t explode during cremation. The fleshy parts of the head like the brain do combust and vaporize but because the skull has gaps, the pressure doesn’t get high enough to cause an explosion. However, the skull does crack as it loses moisture and becomes brittle. A crack may form suddenly but is not likely to cause an explosion.
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