Accumulation may sometimes be a metaphor for the layering of knowledge in the initiation process. The carving of a sculpture is only one step in its life, as its surface may receive many later applications to increase into efficacy and secrecy. A boli altar, for example, receives new layers of material with every initiation. The work is like a canvas, ready for the offerings and blessings of its owners' use. Whether as medicinal coatings, organic empowering substances, or miscellaneous accretions that render the object ambiguous, accumulation is one of the most visually dramatic means of conveying the presence of a secret.
African art allows different kinds of containment of the secret.
There are secrets one knows exist, for their presence is made clear by, say, a swelling or protrusion, or a mirror over a cavity. Other containments are concealed. Caught inside the Bembe figure in cat. Luba kabwelulu figures were originally attached to calabashes containing the testimony of oath-taking, such as nail parings and special crystals. In architecture, artworks outside a house announce the presence of secretes contained within.