Cremation is a process of final disposition that uses intense heat to reduce a body to its basic elements. Although the resulting material is commonly called “ashes,” it is not true ash like the residue left after burning wood. The material returned to a family consists of the durable mineral remains of the skeleton. This process transforms the body into a stable, sterile, and manageable collection of inorganic matter.
The Transformation of Organic Matter
The human body is composed primarily of water (about 60% of total mass) and soft tissues like fat and muscle. During cremation, temperatures in the specialized chamber (retort) reach between 1,400 and 1,800 degrees Fahrenheit. This extreme heat initiates the oxidation and vaporization of all organic material. Water converts into steam, and carbon-based soft tissues are consumed, releasing gases like carbon dioxide. This intense thermal reduction effectively removes all soft tissue, leaving only the hard, dense skeletal structure.
The Primary Chemical Composition
The material that survives the high-heat process is almost entirely inorganic, consisting of calcined bone fragments. The chemical identity of cremated remains is dominated by the skeleton’s mineral content. The primary constituent is calcium phosphate, which forms hydroxyapatite, the mineral matrix of bone tissue. This compound typically makes up the majority of the remains, with phosphate often comprising 47.5% and calcium around 25.3% of the total composition. The remains also include trace elements such as sodium, potassium, and magnesium, making the resulting material chemically inert and highly alkaline.
Physical Properties and Volume of Cremated Remains
The material recovered from the cremation chamber consists of bone fragments that are often brittle and porous. Before being returned to the family, these fragments undergo pulverization. This process reduces them into a uniform, granular consistency, resembling coarse sand or fine gravel. The color of the remains can range from white to light gray, influenced by the cremation temperature and the individual’s mineral content.
Volume and Weight
The volume and weight of the remains are not dependent on the person’s pre-cremation weight, as fat and muscle are vaporized. Instead, the final mass is determined by the individual’s skeletal density and size. For an adult, the remains typically weigh between four and eight pounds, representing about 3.5% of the body’s original total mass.
Non-Combustible Materials
Materials that are not organic human tissue may be found among the skeletal fragments after the process. These non-combustible items include metallic surgical implants or dental fillings, such as titanium joint replacements, steel rods, or gold crowns. These items, along with any remnants of the cremation container, are separated from the remains before pulverization. Crematorium staff typically use a strong magnet or specialized sorting processes to ensure only the bone fragments are returned to the family.