Quick Answer
The amount of ash left after cremation depends on the size and weight of the body, but typically ranges from 3-9 pounds for an adult. The cremated remains are mostly comprised of calcium phosphates, the minerals found in bones and teeth. The rest are metals and other minerals that survive incineration. Cremation reduces the body to about 3-7% of its original weight. An average adult male weighing 180 pounds will therefore produce around 5-6 pounds of ash. The amount varies based on body composition.
How Cremation Reduces Body to Ash
Cremation uses high heat to reduce the body to bone fragments and ash. During cremation, the body is placed in a cremation chamber or retort and subjected to flames reaching 1400-1800°F. The high heat causes the body tissues to shrink and decompose, leaving only bone behind. The bones then become fragile and brittle, allowing them to be crushed into smaller fragments.
The bone fragments are further reduced to a coarse powdery ash consisting mostly of calcium phosphates. The intense heat vaporizes the soft tissues of the body, combusts the proteins and melts the fats. The water in the body is evaporated. Over the course of 2-3 hours, all that remains are skeletal remains and minerals that resist incineration.
Stages of Cremation
Cremation occurs in several stages:
| Initial drying phase | The body loses about 70% of its weight as water evaporates. Proteins also begin to decompose. |
| Main combustion phase | The body fat combusts and the organs, muscles and soft tissues decompose. The temperature reaches about 1400°F. |
| Calcinating phase | The soft tissues are destroyed by heat, leaving only skeletal remains. The temperature reaches 1600-1800°F. |
| Ash conversion phase | The skeletal remains break down into fragments and are further reduced to ash. |
At the end, all that remains are 3-9 pounds of ash and small bone fragments depending on the size of the body. The ash is usually light grey in color but can be white or darker grey.
What is Cremation Ash Made Of?
Cremation ash is mostly comprised of:
- Calcium phosphates – The main mineral component of bone and teeth (hydroxyapatite)
- Minor minerals – Potassium, magnesium, iron, sodium, chloride
- Trace metals – Aluminum, copper, zinc
Calcium phosphate compounds account for over 90% of bone mineral content. When the soft tissues burn away, the calcium phosphates remain behind along with metallic elements.
The following table compares the chemical composition of an average human body before and after cremation:
| Component | Before Cremation | After Cremation |
|---|---|---|
| Water | 63% | 0% |
| Carbon | 20% | 3% |
| Calcium | 1.5% | 37% |
| Phosphorus | 1% | 14.5% |
| Potassium | 0.35% | 1.5% |
| Sodium | 0.205% | 0.9% |
| Chloride | 0.142% | 0.5% |
| Magnesium | 0.027% | 0.7% |
| Iron | 0.006% | 2.1% |
| Zinc | 0.003% | 0.8% |
As shown in the table, calcium and phosphorus content increases dramatically after cremation while carbon is reduced. Water and organic compounds are eliminated after combustion.
Difference Between Bone and Ash
There are two key differences between whole bone and cremated bone ash:
- Cremated ash has higher mineral content because the organic collagen matrix of bone burns away.
- The crystal size of hydroxyapatite is smaller in ash due to the effects of heat.
So while their chemical makeup is similar, ash is more mineralized, porous and powdery in texture relative to intact bone.
What Affects the Amount of Ash?
Several factors account for the variability in the amount of cremation ash produced.
Body Size
Larger bodies with bigger skeletons will produce more ash than smaller bodies after cremation. The typical range is:
- Infants – 3-4 pounds
- Child – 3-5 pounds
- Adult female – 4-7 pounds
- Adult male – 5-8 pounds
- Obese individual – 8-10+ pounds
The more bone mass present, the greater the ash weight. Men tend to have denser, heavier bones than women.
Age
Younger people’s bones will produce more ash than elderly remains, since bones lose mass and become more brittle with age. An adult in their physical prime will yield the most ash.
Cause of Death
Those who die from wasting illnesses or bone-depleting diseases will be cremated into less ash. Certain cancers, kidney disease, and osteoporosis can diminish bone density.
Cremation Conditions
Modern crematories reduce bodies to ash in under 3 hours at 1600-1800°F. Higher temperatures and longer duration will yield finer, lighter ash. If some bone fragments remain, the ash weight increases.
Prosthetics and Implants
Metal joint replacements, pacemakers, plates, screws, dental fillings, and breast implants will not burn away, contributing slightly to the ash weight.
Is Amount of Ash Meaningful?
Some people attach special meaning or symbolism to the ashes, but there is no scientific correlation between the ash amount and the person’s body or personality. More robust skeletons will simply produce more bone ash residue after cremation. The quantity of ash should not have spiritual significance.
Ash Color Variations
While bone ash is usually greyish-white, the color can range from pale white to charcoal. Color variations are caused by:
- Temperature and heating conditions
- Presence of soft tissue residue
- Incomplete processing of bone
- Chemical reactions with casket/container
Darker ash indicates higher carbon content and less complete combustion. Very white ash signifies complete oxidation of all carbon. Bone color can also influence ash color. The ash color has no real significance relative to the deceased.
What Happens to Unclaimed Ashes?
If no one claims the ashes after cremation, funeral homes usually hold them for a period of months to a few years. If they remain unclaimed, the ashes may be scattered or buried, often in a common grave or cemetery plot. Many crematories now scatter unclaimed ashes at sea. States have different laws regarding retention and disposition of abandoned ashes.ASH SCATTERING
Ash Scattering and Burial
Cremation ash can be dispersed in many ways. Common ash scattering options include:
- Burial in an urn in a columbarium or cemetery plot
- Scattering in a meaningful nature location like mountains or sea
- Scattering on family land or where loved one wanted
- Retaining in an urn as a memorial
- Incorporating into objects like jewelry or art
- Intermingling ashes from multiple family members
If scattering on land, ashes should be dispersed widely and discreetly. Scatter on private property or obtain permission for public areas. Ash is sterile but for aesthetic reasons should not be noticeable. People choose locations with personal significance to the deceased.
Is Ash Scattering Legal?
Most states allow ash scattering but have regulations on locations and permit requirements. Typically allowed places include:
- Private land with owner consent
- Cemeteries
- Public land with permits like parks, forests, and beaches
- Scattering at sea, often 3+ miles offshore
Many states prohibit scattering on roadways and public lakes. Check local regulations before ash scattering. Inform family of the location in case they want to visit or recover the ashes.
Cremation Ash Burial
Instead of scattering, some families choose to bury or intern the ash in a cemetery. The cremains are placed in a container like an urn or box that is then buried underground. Many cemeteries have columbaria with niches for urn storage. Families can visit and be comforted knowing the location.
Conclusion
On average, cremation reduces the body to around 3-7% of its original weight. Adults will yield approximately 4-8 pounds of bone ash depending on their size and age. The ash consists primarily of calcium phosphates from theskeleton with trace metals. More bone mass means more ash, so larger bodies produce more cremated remains. While variable in color, the quantity of ash has no spiritual meaning. Cremation ash can be buried, scattered, kept in an urn or incorporated into other memorials.