This week’s lab was a continuation of week 7’s lab, during which we constructed clay pots out of both refined studio clay and less refine clay from the Carleton arboretum. Below is the data we collected and the procedure of the lab.
|Side Thickness (in.) (Pre-fire/Post-fire)||Diameter (in.) (Pre-fire/Post-fire)||Height (in.) (Pre-fire/Post-fire)||Weight (g) (Pre fire/Post Fire)|
*pots that decreased significantly in weight lost sizable chunks in the firing process
As can be observed from the data, both the normal clay pots (1-5) and the arboretum clay pots (6-8) remained basically the same size and weight, with the exception of some shards. Most of the other pots fired by our group remained mostly intact, and luckily all of our test pots did as well.
1:45-2:20: Materials gathered for the first fire. This includes cabinet wood, bark, small logs, and newspaper. The coals of first fire will be used to create a hot bed to rest the pots on during the firing.
2:20: The fire is lit.
2:21: Fire temperature is measured, results are inconsistent but seem to be around 600.
2:25: Pots are moved closer to the fire.
2:32: Pots are getting much warmer and are uncomfortable to touch.
2:38: Some pots start to turn a blueish color on sides nearest to the fire
2:42: Fire temperature is now too high for the thermometer to read (>999).
2:43: Some of the wood is jostled around to promote quicker breakdown into coals.
2:46 Pots placed on bed of ashes. One pot breaks almost immediately, but the others are fine. Pot temperature is 200 degrees, the coals are 800 degrees.
2:49: Second fire, more of a pyramid structure, is built around the pots, it lights because the coals are still hot.
2:51: Popping noises are heard from beneath the wood. Unsure if wood or clay but sounds more like clay.
2:53 Gaps of the pyramid structure are filled.
3:06: Fire still burning.
3:09: Fire temperature again too hot for the thermometer to read, flames are significantly taller than the first fire.
3:20 Fire seems not as tall now, but is still very hot. We have not heard any popping noises in a while at this point.
3:40: Fire smothered with sawdust just as it starts to rain. Sawdust puts out the the fire quickly and there is little smoke. The other smothering materials seemed to not work as quickly as the sawdust and allowed for more smoke to rise.
We returned to the site of the lab during the next day’s class. Overnight, our group’s fire pit re-lit at around 5-6am and had to be re-smothered. The pots were beneath ash and we needed to carefully search through the ash to try and find the pots. We need to be careful because there is a chance that the fire will re-light on the spot.
Luckily, our group’s ash did not re-light. After several minutes of searching, we uncover the first pots. After a few more minutes of clearing, we found all the pots.
No other pot completely shattered except the one that made the popping sound in the fire yesterday. However, all of the regular clay pots had small cracks in them, most of which appeared on the bottom of the pots. The regular clay pots became a gray color that is from the reducing stage of the fire. The arb clay pots did not change color as much, but none of them cracked.