Focus on this artwork and discuss the Egyptian faience.
Related to glass insofar as it attains a "vitreous" appearance, Egyptian faience was, according to David F. Grose, "a material made from powdered quartz covered with a true vitreous coating." Significantly more porous and malleable than glass proper, faience could be shaped by hand or cast in molds to create vessels or other objects. While similar raw materials are involved in the creation of both faience and glass (crushed quartz or sand mixed with lime and either natron or plant ash), faience ultimately lacks the rigid crystalline structure of modern glass. Significantly, both glass and faience were used, according to Paul T. Nicholson, to imitate semi-precious stones in less costly materials, and both were valued for their beauty and durability.  Although not pottery on a strict definition, since it contains no clay, faience is often treated as pottery.
This statuette demonstrates the importance of a variety of iconographic styles in Middle Kingdom era burial practices. As Nicholson writes, animal figures were common during this period and "hippopotamus figurines, usually decorated with aquatic plants, probably symbolized the revitalizing properties of the Nile". They may have held some kind of religious significance, as they were sometimes associated with one of the forms of Seth. As not all hippopotamus statues from this era were elaborately painted, William is a particularly important example; he has been "covered with a decoration in black line of lotus flowers, buds, and leaves" to signal his "natural surroundings among the lowlands of the Nile." As noted in the Metropolitan Museum's summary, the hippopotamus was one of the most threatening animals for ancient Egyptians and, in this case, three of William's legs probably were broken purposely to prevent him from harming the deceased in the afterlife (the museum restored these legs).
hippopotamus clay Egyptian faience David F. Grose Seth pottery natron Middle Kingdom