Ancient Egyptian embalmers removed moisture from the body using natron, a naturally occurring salt that draws water out of tissue through osmosis. The process took weeks and reduced a body’s weight by roughly two-thirds. But the Egyptians weren’t the only ones to solve this problem. Nature, chemistry, and modern science have each found distinct ways to pull water from human remains and stop decay in its tracks.
Why Removing Moisture Matters
The human body is about 60% water, and that water is exactly what bacteria need to break tissue down. Decomposition is essentially a race between moisture and drying. If the environment or a chemical process can pull water out of cells faster than bacteria can multiply, the body preserves instead of decaying. Every preservation method, ancient or modern, works by winning that race.
How Natron Dried an Egyptian Mummy
Natron is a mineral salt found along dry lake beds in Egypt. Its active ingredients are sodium carbonate and sodium bicarbonate, with traces of regular table salt (sodium chloride) and sodium sulfate mixed in. When packed around and inside a body, these salts create an intensely concentrated environment outside the cells. Because water naturally moves from areas of low salt concentration to high salt concentration, fluid gets pulled out of every cell in the body, through the skin, and into the natron. The same basic principle is at work when you salt meat to cure it.
Before applying natron, embalmers first removed the organs most likely to rot quickly. They pulled brain tissue out through the nostrils using specialized hooked instruments, then made an incision on the left side of the abdomen to extract the stomach, liver, lungs, and intestines. These organs were preserved separately in containers known as canopic jars. The heart was left in place because Egyptians considered it the seat of intelligence and identity.
With the body cavity empty, embalmers packed natron inside the torso and skull, then covered the entire exterior in more natron. This wasn’t a liquid bath. Researchers have noted that submerging a body in a natron solution would actually be counterproductive, since the goal was dehydration. Dry natron, heaped over and stuffed into the body, worked far more effectively.
A 13-year experiment using a pig carcass (similar in size and composition to a human body) showed how dramatic the weight loss is. The body lost about 30% of its starting weight within the first 200 days. By seven years, it retained only about 37% of its original weight. After 13 years, it had stabilized at roughly 35%, losing just 140 grams every six months. Most of the moisture came out in that first intensive drying period.
What Happened After Drying
Once the body was fully dried, embalmers washed off the remaining natron and repacked the empty cavities to restore a lifelike shape. The materials used varied, but imaging studies of child mummies have revealed mixtures of linen, sawdust, sand, mud, chopped straw, lichen, and even onions stuffed into the torso and skull. Resin-like embalming substances were poured in as well, sometimes entering the cranial cavity through the nasal passages. Textile tampons were occasionally packed into the nostrils. These packing materials absorbed any residual moisture and helped the body hold its form under layers of linen wrapping.
Natural Mummification Without Salts
Embalmers weren’t always necessary. In extremely dry, hot climates, bodies can mummify on their own. The key conditions are low humidity and enough heat to evaporate water from the skin faster than bacteria can colonize tissue. Researchers have documented natural mummification in environments as varied as the Egyptian desert and temperate coastal South Africa, where temperatures occasionally spiked above 32°C. The critical factor isn’t a specific temperature threshold but the balance between drying speed and decomposition speed. A body buried in dry sand with good airflow can lose moisture quickly enough to preserve skin, hair, and even internal structures without any chemical treatment.
Bog Bodies: Preservation Without Drying
Not all preserved bodies are dried out. Bog bodies, found across Northern Europe, represent a completely different approach to stopping decay. In raised bogs that receive water only from rainfall, the environment is extremely acidic and nutrient-poor. A moss called Sphagnum dominates these bogs and produces a molecule called sphagnan that essentially tans human skin the way leather is tanned. Sphagnan also binds calcium and nitrogen, pulling calcium out of bones until they become soft and rubber-like.
The result is the opposite of a mummy: the skin, hair, nails, and internal organs survive beautifully, but the skeleton dissolves. In contrast, bodies deposited in lower, mineral-rich bogs that receive groundwater tend to lose all soft tissue while their bones remain intact. The chemistry of the water determines which parts of the body survive.
Plastination: The Modern Method
The most precise modern technique for removing moisture from a body is plastination, developed in the late 1970s and used today for medical education and public exhibitions. It replaces water with plastic in three stages.
First, the specimen is submerged in acetone, a volatile solvent that enters cells and displaces all the water inside them. This step typically takes around 72 hours. Next comes forced impregnation: the acetone-filled specimen is placed in a vacuum chamber filled with liquid silicone. As the vacuum lowers the pressure, acetone evaporates at room temperature, and the pressure difference pulls silicone into every cellular space the acetone just vacated. This step can run for about 42 hours under carefully controlled vacuum pressure. Finally, the silicone-filled specimen is heated to cure the polymer, locking it permanently in place.
The end product contains no water at all. Every space once occupied by moisture is now filled with solid silicone, preserving the original anatomy down to the cellular level. Unlike a mummy, which is shrunken and brittle, a plastinated specimen retains its original size and can be handled without damage.
How the Methods Compare
- Natron (Egyptian mummification): Draws water out through osmosis over weeks to months. The body shrinks significantly and becomes dry and rigid. Organs are removed first to speed drying.
- Natural desiccation: Hot, dry air evaporates water through the skin. No chemicals needed, but conditions must favor drying over bacterial growth. Results vary widely depending on climate.
- Bog preservation: Doesn’t remove moisture at all. Instead, acidic, oxygen-poor water and plant chemicals halt bacterial activity and tan soft tissue in place. Bones dissolve while skin survives.
- Plastination: Replaces water molecule by molecule, first with acetone, then with silicone. Produces the most anatomically accurate preservation, with no shrinkage or distortion.
Each method solves the same fundamental problem: water inside the body feeds the bacteria that cause decay. Whether you remove it with salt, evaporate it with heat, chemically neutralize it with acid, or replace it entirely with plastic, the principle is the same. Stop water from being available to microorganisms, and decomposition stops with it.