(Sorry, couldn't help it)
Here's an interesting topic. I expect most Americans will recall the derivation of the name Assiniboin, but this, of course, a practice with some geographical sweep and temporal depth.
Reconstruction archaeology on stone-boiling:
Experiments by Michael O'Kelly on the basis of Irish prehistoric evidence have shown that 100 gallons of water in a wooden-lined pit could be brought to the boil by this means in a mere 30-35 minutes. A 10lb. piece of meat could be cooked in 3 hours 40 minutes.
Well, you might have to watch which stones you used for the purpose or you could, indeed, ingest sharp fragments. Some prehistoric sites have a great deal of burnt flint, and the pieces were traditionally referred to as pot-boilers. People tend not to use the name now, because it's felt that flint wouldn't be suitable for the purpose for just this reason and it probably hadn't been burnt for that.
I would think you'd want round granite-ish rocks. Something that would absorb and hold a lot of heat. Huh, now I might have to kidnap one of Mom's collected rocks for experimentation. It happens to look like an ostrich egg.
From memory granite works go, but is known to explode from time to time from thermal shock.
I haven't used pot boilers myself but I have used pit ovens on land that is on the edge of granite geology (just outside the boundary for dartmoor, uk) and have had most of the stones explode in the fire at some point. Not as spectacularly as I've seen flint explode though when I helped heat treat some flint in france.
From the website Maorifood.com discussing the traditional Maori method of pit cooking:
3. Gear Check List : Stones
When heated the stones will supply the heat for cooking the food, so it is important to choose
stones that do not crumble in the heating or shatter too readily.
The best stones to use are those that have been tried by the local people.
Igneous (volcanic) are better than metamorphic or sedimentary (e.g. sandstone) rocks.
There are several types of rock suitable:
Auckland Blue - this is a type of hard, brittle, blue- metal rock and black rock.
Riverhead Rock - round loaf sized stones are best.
Volcanic Rock - this is the type of rock used during the depression to make stone walls.
It is good rock to use, heats quickly, doesn't throw out chips and is light to handle.
Choosing the rock takes some skill. Take a hammer with you and hit each rock, only those with a high
pitched ringing noise are suitable . Kawakawa Bay and Dargaville are both sites nearest to Auckland.
(some people today use fire bricks mixed with some of the stones mentioned above.)
The number of stones necessary will depend on the type of stone and size.
For up to a party of 25 persons, you will need sufficient to fill a hole approximately 0.5 metres deep.
Tapering from approximately 1 metre in diameter at the bottom (see below "making the hole").
The stones must be thoroughly dried out before use
If you're interested in my (very) occasional updates on how I'm working out and what I'm eating click here.
Lot's of wonderful stuff.
I'd love to try the Maori pit-food.
Here's an interesting cooking practice from Mongolia. They put hot stones inside the animal carcass. I guess that would work even if the ground was frozen too hard to dig up.
If you put rocks that in a fire that's been soaking in water they can explode as the water expands to steam. Since flint is hard I can see it breaking and ceacking if its heated too fast and/or too high a temp and then dropping water. Flint will get brittle as it becomes "glassy". Heat treating flint for knapping was carefully done by first spalling and then slowly heating the flint/chert over a period of hours.
When we stone boiled some shrimp I was surprised how fast it cooked. The stones would boil the several gallons of water as fast as the rocks were dropped in
I guess people think of meat toasted over the embers as the original form of cooking. Maybe it is. However, "boiling" (really simmering) meat in water probably goes back some way. You can do this even if you haven't got fire-proof pots. At the most basic level, you can dig a hole in the earth, line it with a hide, fill it with water, heat the water by dropping hot stones in it, and cook the meat by putting it in the hot water. If we cook by moist heat, then we tend to stew for a long time. That's not necessarily true of people in the past. Some ethnographic accounts indicate some primitive peoples dropped gobbets of flesh into a caldron and fished them out again when they were still quite rare. That throws some doubt on the reconstruction archaeology done in Ireland for me - why a joint rather than cut-up meat? Is this based on the size of the pit -- which (I assume) is based on physical evidence. Why "boil" rather than toast meat anyway? I don't know. Stefansson says that the Eskimo he lived with vastly preferred meat cooked that way. That doesn't seem to be our preference: more light on that would be interesting
Here's one more issue I can think of (doubtless there are many more) -- if you simmer meat in water (or some other cooking liquor) some of the minerals pass into the broth. You then need to bail out the broth in mugs and drink it, if you're not to risk mineral deficiencies. Steve Phinney has some interesting comments on this. In practice, people must suss this out pretty quick. o-r somehow they just intuitively know.
Anyway, lots of interesting issues around this practice. It deserves close attention from soneone more knowledgeable about the archaeological record than I.
The burnt flint I've seen would've been spoiled for toolmaking. However, I can't think I was looking at "potboilers". I don't know why they burnt it: it's a mystery to me.
Last edited by Lewis; 12-07-2012 at 10:36 AM.