Selected Reprints
Boiling Water with Rocks
by Jim Trocchi Many times we jokingly refer to someone who isn't adept at cooking, as someone who can't boil water without
burning it. But to Native Americans, boiling water was a basic and essential skill. Boiling water wasn't simply filling a
metal pot with water and heating it over a fire, because these prehistoric cultures didn't 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 couldn't 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
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 site's interpretation and may tell us a lot more about it. I
think we sometimes don't 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.