During our efforts to identify a replicable manner by which landmarks/semi-landmarks can be applied to archaeologically-recovered ceramics, and during our initial efforts to quantify variations in vessel symmetry, we noticed that when vessels were oriented along the basal plane (akin to sitting atop a table), the majority of vessel rims were tilted to varying degrees.
I could not help but to think of my own experience making coil-built ceramics where rim tilt might be said to occur on a regularly irregular basis. In thinking about it further, I have seen this manner of phenomenon in various phases of excavations (Phase I, II, and II) as well, where the area closest to the excavator is often deeper than the area furthest away from them when the excavator perceives the surface as being flat. While that may be a terrible metaphor, I think we have all run across instances where our perception of an object was skewed by our viewpoint. I think it worth mentioning that some artists regularly capitalize on issues of perception/viewpoint in their work.
It may be the case that we can augment our research into the (a?)symmetry of coil-built ceramics by including a measure of rim tilt. From a fast (and superficial) visual inspection of our sample, it would seem that those vessels appearing low in symmetry also appear to have a higher degree of rim tilt. Whether this will play out in an actual analysis is unknown, but it does seem like rim tilt might be a useful metric.
To calculate rim tilt, we used the basal plane (Plane 1) that we created to identify the widest point of the vessel, and insert a second plane (Plane 3)–using region groups–along the rim. Once the planes are in place, the angle of the two planes can be calculated. Assuming uniform coils, it may also be the case that the shorter side of the vessel is thicker than the higher side.
I wonder whether the lowest point of the rim may have been facing the maker during the manufacturing process? If not a result of skill or expediency, this would mean that rim tilt was an intentional element of vessel manufacture, and may have other implications (was the vessel designed to face a certain direction? See below.).
Image of a bowl used at Genghis Grill that is designed to face in a specific direction (from http://188.8.131.52/~genghisg/wp-content/uploads/slide-img-4.jpg).
If manufactured to face a particular direction, that could have important implications (studies of residue, etc.), but if not, it may point to another possible measure of skill or expediency in coil-built ceramic manufacture. In either case, it is an intriguing attribute of these vessels.