Boiling Water with Rocks
by Jim Trocchi

Many times we jokingly refer to someone who isnít adept at cooking, as someone who canít boil water without burning it. But to Native Americans, boiling water was a basic and essential skill. Boiling water wasnít simply filling a metal pot with water and heating it over a fire, because these prehistoric cultures didnít have metal.

At the time of initial European contact in northeastern North America, Native American container technology had only advanced to clay pottery. This technology was one of the hallmarks of the transition from the archaic to the woodland period. These clay pots couldnít handle direct fire and instead had to handle heat indirectly. Therefore, by filling a clay pot with water and gently adding externally heated rocks, water could be brought to a boiling temperature for cooking without destroying the clay pot.

I watched a video of this process take place. Except for not using an actual clay pot, it was an excellent archaeological experiment. The demo used instead a plastic bucket filled with water, a hearth fire filled with heated rocks, and tongs of wood or antler to handle the hot rocks.

The process goes like this. The heated rocks are transferred from the hearth and added to the bucket filled with water, raising its temperature. Depending on the amount of water in the container, these initial rocks may not get the water hot enough to boil and were removed with tongs once the sizzling sound of temperature change in the water stopped.

With the initial rocks removed, more hot rocks from the hearth are added to the pot of water to further increase its temperature. The process of removing the spent rocks with tongs and adding hot ones off the hearth continues until the water reaches boiling. Raw edibles can now be added for cooking. To keep the water boiling while the pottage is cooking, additional rock removal and replacement continues. The above demo can be viewed at and paging down to the item #102, entitled ďNative Americans Preferred Quartzite for Boiling Stones.Ē Page further through the text for the video demo.

These rocks, whether used to boil water as above or used to line a hearth, are found at many prehistoric archaeological sites. They are referred in the archaeological record as fire cracked rock (FCR) or in England they are appropriately called potboilers. These artifacts can reveal much about a site and perhaps should be held in as much reverence as projectile points. Quartzite, granite or basalt would be the preferred stone to use as compared to sedimentary stone that tend to add grit to the pottage.

The following is a very thorough definition description of FCR:

In archaeology, fire-cracked rock, or FCR, is rock of any type that has been altered and split by deliberate heating. It is a feature of many archaeological sites, particularly in the south-central United States. In many cases, fire-cracked rock results when stones were used to line hearths or were heated to provide a longer-lasting heat-source (similar to a modern hot water bottle).

In other cases, fire-cracked rock results from stone being used to heat or boil water; the stones were heated and dropped directly into water held in containers made of skin or pottery (retrieved from

The definition above also mentions that skins could be used as water containers. Before the Woodland Period and the advent of clay pottery, a container for holding water could be made by digging a crater in the soil and lining it with animal skins to make it impervious to liquids. Containers made in this fashion are said to be found at large game kill sites out West.

Thus, of the many artifacts that we encounter at a prehistoric archaeological site, projectile points seem to be the most exciting and prized to the average researcher. Granted, in association with other artifacts and features, they can tell us a lot about a site. But evidence of FCR can enhance a siteís interpretation and may tell us a lot more about it. I think we sometimes donít give FCR as much attention and analysis as it deserves. It can suggest such things as the long term and sedentary lifestyle of its occupants. Projectile points alone may not be as revealing. Sometimes we may be romancing the wrong stones. Therefore, be careful not to overlook or dismiss lithic artifacts and features that appear unnaturally brittle, cracked or red tinted.