Friday, April 04, 2008

Primitive Pottery and Cooking

Back in late November my crew mate Rosy and I gathered clay from a canyon on one of our day hikes. The clay had washed down through the middle of the canyon. Clay particles, being lighter than sand and dirt, settled on top then dried and cracked. When we gathered it we simply brushed off sand from the bottom of the piece. No purification was necessary.

After gathering the dry clay we put it in a bucket and broke it up into small pieces. We then added water to liquefy it. The clay sat in the bucket (with lid on) until about 2 1/2 weeks ago when we finally decided to use it.

Pure clay pieces gathered from the canyon.

The first thing we needed to do was figure out how much temper material to put into the clay. We used sand from the yard as temper material. Temper is added to the clay to prevent shrinkage when drying and thermal shock when exposed to fire. To figure this out I experimented with different percentages of temper using instructions from In the picture below, the five disks in the upper left corner each have a different percentage of temper from 0%-40%. After air drying them for several days it turned out that they all seemed good. None cracked (too little temper) or crumbled (too much temper).

It wasn't as easy making pots as I hoped. The toughest part for me was adding new coils of clay to a pot and getting it to adhere without squeezing so much that I made the pot too thin. All the creations pictured have 0% temper (which is best for holding water) except the one at bottom center. It was about 20% tempered. My hope was to make it into a cooking vessel. Inside it are beads and a three-legged (one leg fell off) turtle pendant I made. At bottom left is a combination plate/pot lid that I cracked by accident during the drying phase. At top center is a pipe that Kevin made. At top right is Rosy's teapot. The bottom right pot Rosy made using another bowl as a mold.

I meant to add some designs to my creations by pressing leaves on them but I missed that part of the drying phase overnight. I used a spoon to burnish them the best I could which aligned the clay particles making it shiny and better for holding water. After a day of drying some of the pots had small cracks in them. I used leftover clay to patch up mine. It is recommended to dry pots at least a couple days and preferably two weeks. Knowing that the climate is so dry here we probably could have gotten away with 2 days if we wanted. Instead we waited till we got back from our next hitch giving them about two weeks to dry.

From everything I heard and read about firing pots I had the impression that the chances of pots cracking or blowing off chunks during firing was really good so I fully expected to walk away with nothing but the experience. On the firing day there was pretty gusty wind which was bad since sudden changes of temperature (thermal shock) cause cracking and shattering. To counteract this, we set up a wind block as seen in the pictures.

To start we set the pots by the fire to warm them up. Over the course of an hour we gradually moved them closer and rotated them. The goal was to drive out the remaining atmospheric moisture. Heating too fast can cause moisture in the pot to boil which causes shattering.

After the pots were warmed up and dried, we raked the fire out into a ring and put the pots in the middle where the fire had been. For the next three hours we gradually moved the ring of fire in closer until it was totally on top of the pots.

Here you can see how the pots changed color during firing.

I dropped a piece of glass in the fire to test the temperature. Supposedly if you can melt glass then it is hot enough for clay. Unfortunately it melted on a few of the pots. Near the end of the four hours we added a lot of small wood to spike the heat up. Then we let the fire die naturally.

The following day we checked the pots. To our satisfaction none had shattered. All of them had some amount of cracking which isn't surprising given they cracked during the air drying phase. Despite a few hairline cracks, my little cup held water. My cooking vessel dripped water from the bottom, but I was able to cook up a couple eggs in it. It appears the eggs plugged up the cracks too because it now holds water. Overall it was a great success.

While we waited for the fire to die we took the opportunity to cook some meat on the coals. No need for a grill, oven or pan. The coals flake right off.

I also experimented with cooking ash cakes. I mixed flour, cornmeal, raisins and sunflower seeds together with water to make patties. I threw them onto the white ash and a few minutes later they were ready to eat. For more information about how to make them check out the ash cakes article at

4 comments: said...

Very good! I once again enjoyed your latest article.

In my area are some varved clays from a glacial lake that once occupied a river valley. Your ideas have me excited to try this once the ice goes out, which should be within the next several weeks.

ap said...

great post!
sweet pot

fooiemcgoo said...

i didn't know you could do that.

Jarom said...

Take the clay and dig a pit twice the height of the tallest piece and twice as wide as all of the pieces to be fired. Put a layer of saw dust down and put the pots in. Fill the posts with saw dust and keep at least an inch of space between them. Cover with saw dust. build a fire over the saw dust and let it burn for an hour and then let it die. Leave until morning. Your pots will be fired to a bisque level and will be permanently black.

That method is similar to the southwest Californian method (for traditional means, substitute black oak bark for saw dust).

Also, to prevent being too thin walled, make the coils extra damp (the clay that is) and when you put them together pat the coils in place with a wooden spoon. This is a traditional technique too!