Lab Data Week 8: Firing (Group B)

This week’s lab took place over a two-day period. On Thursday, we built fires and placed our pots from week 7’s lab on coals before covering them with more wood, letting that burn to ash, and then smothering our fire. On Friday, we returned to uncover our pots and see the results. Data was recorded based on time of observation, although some observations were not time-sensitive.

Groups A and B worked together on this lab, and although there are recordings for the weight and measurements of pots before and after firing, they were recorded by the group A lab recorder.

Thursday

Time	Observation
2:00-2:16	I help start a fire and am thus not recording other data. Pot measurements are taken. We initially attempt to start the fire using a teepee structure, but this proves unstable and we quickly resort to a lean-to structure, after which the fire burns easily.
2:17	The fire is burning easily, and we place our pots around the edges. Distances range from maybe a foot to about 2 inches. There are 17 pots total, one of which was broken on arrival.
2:18	We add more logs to the fire (read: closet boards).
2:19	We move the pots back to about a foot under Austin’s suggestion. Our temperature gun has difficulties reading the real temperature of the fire or pots and records it as “HI”.
2:21	We decide that the pre-broken pot is a “sacrificial pot”.
2:22	We rotate the pots using long tongs provided by Professor Connole in order to let the pots heat more evenly and hopefully prevent cracks. I can see the heat rippling over the fire.
2:25	We add more wood.
2:26	Professor Connole says that we can be “more aggressive” in our pot heating, and we move the pots closer again, to roughly an inch away from the fire. She also tells us she can tell the pots are less than 200 degrees because she can touch them “comfortably”.
2:28	It starts to drizzle.
2:29	The first log to collapse in our fire falls out and onto the ground; we return it using the magical tongs.
2:31	Group observations: – the fire is “pretty hot”. – there are bits of ash in the pots.
2:34	John observes that the pots are no longer comfortable to touch, suggesting that they are now above 200 degrees.
2:38	We rotate the pots again. Some are becoming bluish around the edges.
2:39	Professor Connole recommends that we warm the bottoms of our pots, as these are frequently thicker and retain more water, leading to cracks. Subsequently, we turn all the pots on their sides, except those that will not balance this way.
2:41	Some pots are showing chips at the edges, either from the rising heat or because we’ve accidentally whacked them too hard with the tongs. Lydia remarks that she feels emotionally attached to the pots.
2:42	Trina tests a large log to see if it has turned to ash; it doesn’t crumble and is “still a solid log”. We retrieve more wood.
2:44-2:45	We move the aforementioned log to the outside of the fire and begin piling our pots on the coals beneath regardless. Pots are added upside down, stacked on top of one another as closely as possible. The larger pots go toward the bottom of the stack.
2:46	One of the thickest, largest pots explodes, producing a loud popping noise that is definitely not wood. It is very dramatic and other groups immediately crowd around.
2:48	A slightly more trustworthy radar thermometer reads our fire at 300 degrees. We begin piling a teepee of wood over our pots, much lower than the other groups — our wood actually touches the top of the pots.
2:50	We’ve covered the pots in wood, but from within emanate the sounds of exploding clay. Given that we can only see maybe two of the pots, we have no idea if it’s the same pot popping over and over, or if all the other pots are currently being turned to shards. We add more wood and pack it with newspaper to help it catch, and there is a lot of tension in the air. One of the two pots we can see is still intact and is blackening quickly. Observations: – “this is the most tense part of the process”. – “none of our pots are gonna survive”. – community spirit still seems to be high; we take bets on whose pots will survive the firing process.
2:55	The fire is really and truly burning hot. No more clay has exploded that we’ve heard since that first minute or so.
2:56	The logs of the teepee are beginning to blacken. The fire is a communal viewing event. John: “This is cool! I’m into it!”
2:57	The logs are getting white at the edges.
2:58	A log falls out of the fire and must be returned with tongs. Temperature rating: “Dude, that’s hot!” (The temperature gun again failed to give a helpful reading beyond “HI”.)
3:01	The logs continue to whiten. There is friendly competition with other groups as to who will successfully shepherd more pots through the firing process. Temperature rating: “Geez, it’s hot!”
3:05	We shift the ends of the logs closer to the main fire so that they will reduce to ash more quickly. Upper parts of the logs have burnt away. Our structure maintains the same overall shape, since it was built resting on the pots, but it is squishing in a bit.
3:08	Temperature rating: “too hot”. The pots are totally covered in ash and burning wood, unlike one method of cremation. We debate whether the bed of coals underneath the pots suggests that this could have been a helpful strategy in cremation.
3:12	The logs are completely white and collapsing into the fire. Sam brings the nice temperature gun again and says our fire is either 950 degrees or just “hot”. We pile up the unburnt ends of wood near the fire again.
3:17	Slightly stronger drizzle, thunder in the distance. While observing the fire, we break off into circles and hold conversation; overall effect is very communal.
3:23	The fire approaches readiness for dousing. In preparation for this, we retrieve our assigned smothering material, sawdust (made of ash, oak, and walnut), which comes in a massive trash can. We retrieve a smaller bucket to facilitate not getting sawdust literally everywhere. Lucy: “[the fire] is so glowy”.
3:35	We turn over the remaining logs in the hope that this will reduce them to ash faster. I accidentally uncover a pot (still whole!) in the process but cover it again. I would definitely call this rain and not a drizzle now.
3:39	Downpour.
3:40	Given the sudden rain, we give up on waiting for all the logs to turn completely to ash and decide that it is “smother time”. We run out of the tent where we’ve taken cover holding the trash can of sawdust and the smaller bucket. The first two buckets of sawdust merely induce the fire to burn higher, but after buckets five and six the oxygen supply is cut off enough that neither flames nor smoke are visible. Adam, watching the other groups smother their fires: “having the sawdust was really good”.
3:47	We return to the tent. Observe the other groups smothering their fires, engage in mild competition.

Friday

Time	Observation
6:00	We weren’t there, obviously, but we hear that at this time the smother sawdust had turned to ash and fire sprang up again. This was smothered in more fresh sawdust for us.
11:10	The ash pile is “still warm” to the touch. Professor Connole warns us not to remove the pots from their warm spots in the ashes too suddenly or the thermal shock could break them.
11:12	We brush the sawdust and ash off of the pile using our hands and the magical tongs. The ash pile is still smoking faintly.
11:15	We uncover the first of our pots.
11:17	Temperature rating of the pots: ~125 degrees. They are hot to the touch and feel “solid”. Colors are smoky dark grays with clouds of black and paler gray; one Arb clay pot is still earthy brown and another has brighter brown spots on the inside. Many sides and bottoms of pots, where the clay was thicker and less likely to have dried, have chips spalled off. 15/17 pots are still recognizably intact and usable, meaning that only the pre-broken pot and the one that exploded immediately suffered significant damage. The Arb clay pot survival rate, in general, is impressive. Not only are we 3/3, but none even had chips taken off, despite the thickness of the walls. Maybe because they’re smaller?
11:26	The pots, although still warm, are cool enough to touch easily. Breaking shards of clay reveals that they were baked all the way through — the color is solid. Pieces of pots chip off when they rub against on another.