It's a natural phenomenon that has puzzled people for thousands of years. Why do some corpses decay, while others extrude a thick wax, preserving the body inside for centuries?
Bury a body in most soil, and bacteria will get to it. They'll be able to thrive, because there's plenty of oxygen around the body. Over a couple of decades, they'll break the body down so nothing is left. Let's say, though, that the corpse isn't in a place with lots of oxygen available. Typical bacteria won't be able to thrive - but there are anaerobic bacteria that can live without air. Still, there are a lot of tissues in the body, and bacteria aren't the only ones that go to work on them.
The environment that usually degrades a body can, in some cases, make it form a hard outer shell that keeps it fresh for centuries. When water hits fat, it can start a process called hydrolysis. The water molecules split the fat molecules and recombine them. There's also the process of hydrogenation, in which hydrogen combines with fat molecules to make them harder. Hydrogenated and hydrolyzed fat coats the outer body, sealing it off inside. It also seals off any sediments or other evidence with the body.
How to Grow Corpse Wax
Once corpse wax showed people how long, and how well, bodies could be preserved, scientists devoted time and effort into making some. A few of the studies on adipocere looked at pig adipose tissue, and how that developed wax under the right conditions. Others threw caution (and gag reflexes) to the winds and rounded up some human tissue to study. These researchers examined different pH levels, temperatures, and soil types, to figure out the conditions that encourage corpse wax. Ultimately, they found a handy way of growing this gruesome substance.
Yes, submerge a body in "warm" tap water for eighteen months, and the wax begins to form. The temperature doesn't even have to be that well controlled. Anything from twenty-one to forty-five degrees centigrade will get wax going. In about eighteen months, the wax will be visible. After that, what you do with it is your own business - just don't ever tell me.
The Growing Corpse Wax Problem
While scientists were puzzling over a way to grow corpse wax, it turned out that plenty of places in Germany were doing it without even trying. Unfortunately, those places were graveyards. Even more unfortunately, those graves were set to be "recycled."
Many people want a burial, but few have the familial juice to keep their grave tended (or even visited) for more than a few decades. Some graveyards in Germany were set up around this concept. People were buried on the understanding that, about thirty years after their deaths, the grave would be reused for a new body. By that time, generally any body is topsoil, so there was no need to worry about overcrowding.
That is, until people dug down and their shovels hit corpse wax, with a well-preserved body inside. The land used for graves was not the kind of land that anyone would use for anything else. Its soil was wet and sandy, and didn't support much air or life. As a result, the bodies never decomposed, and so there were graveyards full of corpse waxed bodies. People are still wondering what to do with them.
Cemetary Image: Derek Harper