Group A Lab Data

For our lab this week, we fired pots we made last week in kilns we constructed. The pots were made of “arb clay,” or clay extracted from the college’s arboretum, and from standard, regular clay that a beginner might work with due to its ease of handling. We were broken up into three groups to do this lab. We all underwent the same construction process of the pots during this lab and followed the same steps to construct our kilns and then fire the pots on them. The only variable between the three groups was the material used to smother the kiln fire at the end of lab on Thursday. My group, made up of Group A and Group B, had sawdust as our smother material.

The data this week includes pot dimensions of both the pots made of regular and arb clay, and time stamped activities of the lab on Thursday. On Friday, we extracted the pots from the fire and observed them, so the recording of time was not as critical. Notably, the results my group saw on Friday in our pots likely differ from the other groups due to the impact of the smother material.

Regular Clay pot measurements

Wall Thickness in inches (Pre-fire/Post-fire)Diameter in inches (Pre-fire/Post-fire)Height in inches (Pre-fire/Post-fire)Weight in grams (Pre fire/Post Fire)
Pot 1.25/.253.75/3.752/2156/153
Pot 2.22/.224.25/4.251.75/1.75186/194
Pot 3.25/.252.75/2.752/2170/161
Pot 4.25/.253/32.75/1.8240/150
Pot 5.375/.3753.75/3.752.5/2.5214/160
Interesting things from this chart: the weight of most of the pots decreased due to various amounts of the pots breaking off in the fire. However, pot 2 that gained weight is rather inexplicable and may be due to an inaccurate measurement on the first day. Any changes in measurements are also due to shards of the pots breaking off in the fire.

Arb Clay pot measurements

Wall Thickness in inches (Pre-fire/Post-fire)Diameter in inches (Pre-fire/Post-fire)Height in inches (Pre-fire/Post-fire)Weight in grams (Pre fire/Post Fire)
Pot 1.25/.252.75/2.751.75/1.75117/126
Pot 2.25/.252.75/2.751.75/1.6121/117
Pot 3.25/.252.5/1.51.75/1.75167/159
Similar to the regular clay pots, any decrease in the weight is due to pieces of the pots breaking off in the fire, and any increase in the weight of the pots seems likely due to measurement errors on the first day.


1:45-2:20: We gather material and make our fire out of wood, bark and newspaper. This fire will be used to break down the fire-making materials in order to create a bed of sediment to rest the pots on. Our fire gets going relatively quickly once the materials are all in place.

2:21 : We measure the fire temperature. The thermometer reading is jumping around but seems to be reading generally around 600. During this time, Kelly tells us we can place our pots closer to the fire to make sure they are sufficiently warmed before going in the kiln.

2:32 Pots are getting much warmer and are uncomfortable to touch

2:38 Pots start to turn a blue color in areas of the pot that are nearest to the fire

2:42 : The temperature of the fire is too high for the thermometer to read.

2;43: We try to break down the wood that hasn’t broken down yet into sediments, but it does not work as the wood is not yet burnt enough. But the majority of the wood and bark has already broken down.

But some wood and bark is already broken down into coals

2:46 We put the pots on the fire over the bed of sediment and one pot immediately breaks. It was a relatively thicker pot. The temperature of the pottery is 200 degrees, the coals are 800 degrees.

Pre-fired pots on the bed of sediments. Notice the tan color– this will change!

2:49: We now start to build the triangle structure around the pots

The triangle structure around the fire

2:51: We hear more popping noises.

2:53 We fill in the gaps of the triangle structure we built around the pots.

2:55: The fire is really going at this point

2:56 The wood on the fire is totally black.

3:06: Fire is still burning strong.

3:09: The temperature of the fire is too hot for the thermometer to read and the flame is very tall.

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: We smother the fire with sawdust because it starts to rain very heavily. The sawdust puts out the the fire pretty immediately and there is relatively little smoke. The other smothering methods seemed to not work as quickly and to produce more smoke.  

Eryk expertly smothers the fire!


We return to the site of the lab at 11:10 am. We are told that overnight, our fire pits re-lit at around 5-6am. As a result, the pots are now under ash and we need to very carefully comb through the ash with raking tools to try to retrieve the pots. We need to be careful because there is a chance that the fire will re-light on the spot.

Combing through the ash to expose the pots

My group combs through the ash without any fire lighting. After several minutes of combing, we start to see the first pots. After a few more minutes of clearing, all the pots are exposed.

The pots have all turned a gray color to some extent, except for the arb clay pot in the back of the photo.

We see that no other pot completely shattered besides the one that popped in the fire yesterday. However, all of the regular clay pots have small cracks on them, and most of these cracks appeared on the bottom of the pots. The regular clay pots are now a gray-ish color that Nancy tells us is from the reducing stage of the fire. The arb clay pots did not turn this color as much, but also, none of the arb clay pots shattered. This is very interesting and raised the question of whether or not the arb clay pots effectively fired under the time constraints.

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