The term “ashes of a person” commonly describes the substance remaining after modern cremation, but this description is scientifically misleading. The material returned to a family is not the light, flaky residue created by burning wood or paper. These remains are concentrated mineral matter left over from the deceased’s skeletal structure after exposure to extreme heat. This process reduces organic materials to their most basic inorganic components.
How Cremated Remains Are Created
The reduction of the body into cremated remains occurs within a specialized high-heat chamber, often called a retort. This process is essentially one of rapid oxidation and evaporation, which targets the organic compounds that make up the vast majority of the human body. The body is approximately 60% water, and this content is vaporized first as the temperature inside the retort rises.
The temperature within the cremation chamber is maintained between 1,400 and 1,800 degrees Fahrenheit. At these temperatures, all soft tissues, including organs, muscle, fat, and skin, are reduced to gases and trace amounts of carbon. These gases are processed through the exhaust system, leaving behind only materials resistant to intense thermal conditions. The dense, mineralized framework of the skeleton is the primary material that survives this heat.
The duration of the process depends on factors like the individual’s body mass and bone density, but the goal is the complete consumption of all organic matter. Once the cremation is complete, the remaining contents of the retort are not a fine powder, but rather the dried, brittle fragments of the skeleton. These fragments are collected as the total physical remains of the deceased.
The Chemical Makeup of Cremated Remains
The substance commonly referred to as “ashes” is almost entirely composed of the inorganic material that formed the bone structure. This material is primarily calcium phosphate, derived from the hydroxyapatite mineral found in living bone tissue. The heat of the cremation process transforms the bone’s mineral matrix into a highly stable form, specifically tri-calcium phosphate.
Chemical analysis shows that phosphate makes up the largest proportion, often around 47.5% by weight, with calcium accounting for approximately 25.3%. These two elements are the main building blocks of the skeletal system. Other elements present in trace amounts include sulfate, potassium, sodium, and chloride, which survive the high temperatures as various salts and oxides.
Physically, the material that emerges from the retort is granular and coarse, resembling small pieces of gravel or crushed seashells rather than the soft, dark powder of wood ash. The color of the unprocessed fragments is generally white, light gray, or tan, depending on the exact temperature and duration of the exposure.
The final mass of the cremated remains averages between four to six pounds for an adult, representing about 3.5% of the body’s original mass. The weight is closely correlated with the height and bone density of the individual, since the length and size of the skeleton determine the final volume of the mineralized fragments.
Preparing the Final Remains
After the skeletal fragments have cooled, they undergo a final preparation phase before being returned to the family. The first step involves the careful removal of any non-bone materials that survived the heat of the retort. This typically includes metal items such as surgical implants, dental fillings, screws, or temporary medical hardware.
Crematory operators use magnetic wands and manual sorting to separate these metallic remnants from the bone fragments. These non-organic materials are generally recycled according to state or local regulations. The remaining bone fragments are still irregular in size and texture, making them unsuitable for many memorialization options.
The final step is pulverization, which involves using a mechanical processor known as a cremulator. This machine grinds the brittle bone fragments into the uniform, fine, sand-like texture recognized as cremated remains. This grinding ensures the consistency and density of the material, making it easier to handle, scatter, or place into an urn for return.