One of the odd things about prehistoric pottery from Maine is that the potters made one form exclusively: large, open mouthed, round-bottomed vessels with a capacity of two to four quarts.
Why no cups? Why no bowls? Why no mugs? Why no plates or platters? Why no sculpture?
Nobody knows. All we know is that based on shards found, with the exception of some tobacco smoking pipes, prehistoric Maine potters appear to have not made any of the above objects from clay. Apparently, they only made tall, open mouthed vessels. There is no question these various forms could have been easily made with the same techniques and materials used to make the large vessel forms that prehistoric potters did make. And there is no question that cups, bowls, mugs, plates etc. made from fired clay would be useful and long-lasting. But from all of the prehistoric pottery shards ever found in Maine, none seem to be from these common types of ware.
So why no cups or bowls?
One possible reason could be that these large open vessels were only made and used for ceremonial and/or religious events and were not made or intended for everyday use. In keeping with special purpose of these vessels it might have been considered a violation of ceremonial tradition to use fired clay for other objects. Given that smoking pipes are the only other object known to be made from clay by prehistoric Maine potters, it is possible that these pipes themselves were only used on ceremonial occasions and everyday use was frowned upon.
Am I satisfied with this explanation? Not really. Without independent evidence, there is no way to falsify it, and unfortunately we know very little about the ceremonial traditions of prehistoric people in Maine several thousand years ago, when many of these pots were made.
A more mundane explanation would be prehistoric Maine people did not make cups, bowls, plates etc. from fired clay because they didn't feel any compelling reason to make them. Perhaps the various non-clay materials prehistoric people used for these items were deemed functional enough to not warrant replacing them with the same objects made from fired clay.
It has been conjectured that large open, mouthed vessels of fired clay of the type made by prehistoric Maine potters would be useful for cooking food on a direct flame, with small burning sticks placed around the base of the vessel where its rounded bottom was buried in sand, gravel or soil. A 1585 painting by John White, a European visitor to North Carolina, depicts a tall open mouthed vessel with a small fire built around its base. The caption of the painting reads: "The seething of their meate in Potts of earth." (Bourque et al. 2001).
The depiction in this painting is questionable because the clay body and firing method used by prehistoric potters would make a large cooking vessel very susceptible to cracking and shattering when exposed to direct flame. This is true even with modern stoneware. Clay vessels that can withstand the thermal shock of heating by direct flame are called "flameware" and require a unique clay body, usually made by including the rare lithium minerals spodumene and petalite which have an extremely low thermal expansion coefficient (Lawrence & West 1982).
Contemporary experience with earthenware clay bodies of the type used by prehistoric Maine potters suggests that heating by direct flame as depicted in the 1585 watercolor painting would have to have been done with very low, slowly applied heat to prevent cracking, especially because prehistoric Maine pots had thin walls for their size. In addition, because earthenware clay is semi-porous and the vessels were filled with water (to make a stew), there would be a high risk of water trapped in the clay turning into steam upon direct heating, expanding and exploding the ware as it tried to escape. Most prehistoric Maine pots use a large amount of coarse, angular crushed quartz temper in the clay. This temper was most likely added to allow the efficient escape of water in the pore spaces of the unfired pot during the early stages of firing, thereby reducing the chance of cracking and shattering. The same tiny fissures and crevices created by the use of rough quartz temper would allow water to infiltrate into the clay body when the vessel was filled with water for cooking. As the pot was heated by direct flame on its outer surface, the water in these tiny fissures would turn to steam and most likely crack the ware.
Given the substantial risk of cracking by exposure to direct flame, it seems more plausible that prehistoric people heated the contents of these pots by dropping superheated stones into the vessel whereby the stone would release its stored heat into the water. This method would eliminate the risk of cracking of the ware due to heat stress.
Alternatively, the same coarse quartz temper may have prevented the shattering of the cooking pot during direct heating by creating a uniform, evenly spaced series of channels and fissures that allowed water absorbed by the pot to quickly escape and evaporate without turning into steam. The best way to test this would be to make a similar clay body with a similar diameter, type and density of temper, fire it, and test it on a small cooking fire. This has not yet been done.
The inability of earthenware pottery to withstand heating by direct flame without cracking and shattering may be one reason why there are no eyewitness observations by European visitors of Indians making and firing clay pots. Bourque (2001) theorizes that the ability of metal cooking pots and kettles to withstand heating by direct flame may have encouraged Contact Period Indians to abandon their use of fired clay vessels as soon as they obtained metal cooking pots from visiting European traders.
Because the number of shards of prehistoric ceramic pots in Maine is fairly low and their time of use extends across two millennia, it is difficult to estimate how often these pots were made and how widely they were used. Were these pots very commonplace items or were they rather scarce, even during the time they were used? Were they "specialty items" or made routinely and often? Did everyone use them or just some people? Did they have cultural or ceremonial significance or were they just a pot you cooked in? Did every family group have a potter and apprentice? Did some family groups not even bother making them? How long did they last before breaking? And why did nobody, apparently, ever make a cup?
Bourque, B., S. Cox, R.L. Whitehead. 2001. 12,000 Years: American Indians in Maine. Univ. of Nebraska Press.
Lawrence, W.G., R.R. West. 1982. Ceramic Science for the Potter. Chilton Book Company, Radnor, Pennsylvania.