It is actually a batch of Terra Sigillata made from some clay I dug.The clay is deflocculated and allowed to settle for 20 hrs . then the top 1/2 of the slip is siphoned off and the rest is discarded The watery slip is thickened through evaporation until right for use. The screen is there to keep out bugs, rodents. small children and other pests. Terra Sigillata is delicious with pasta and garlic dishes.
Terra sigillata is a very smooth, lustrous coating of clay which resembles a glaze and is virtually waterproof. The name means "sealed earth" and has been used to refer to the Classical Greek Attic black-figure and red-figure painted pottery.
These days, the name terra sigillata is used to refer to an especially fine coating of clay applied to a ceramic piece. For my work only the finest coatings need be applied.