Courses / Sculpture I
Modelling, Moulds and the Workshop

Structure, Armature and the Centre of Mass

Sculpture I 342 words Free to read

Standing Up Is a Design Problem

A sculpture must stand to exist. The physics is straightforward to design with directly.

An object is stable while the vertical line through its centre of mass falls inside its base of support. Tip it, and the centre rises. Tip it further, and this vertical line crosses the base edge. The object then falls. Three consequences follow:

The practical measure is the tipping angle. This is the angle a piece can lean before its centre leaves the base.

The Armature

An armature is an internal frame that supports soft clay. Clay slumps easily under its own weight.

For ceramics, the armature must come out before firing. Clay shrinks during drying, but rigid armatures do not. A fixed core will crack the piece.

ApproachHow it works
Removable armatureWithdrawn at leather-hard stage; cavity is closed
Cut and hollowModelled solid, cut apart, hollowed, and rejoined
Combustible corePaper or foam that burns out in the kiln
Build hollow throughoutBuilt using coils or slabs with no internal core

For work that will not be fired, the armature stays inside. You can use wire, pipe, or wood. Hang butterflies—small wooden crosses on wire—to support clay across long spans.

Designing the Support

You have three main design strategies for stability:

An unstable-looking piece can still stand securely. You must arrange the mass precisely so the centre stays over the base.

Common pitfall: designing the form and then trying to support it. Settle the mass, base, and armature together with your initial design.
Structure, Armature and the Centre of Mass

Practise this lesson

Try the questions below, free, answers included. The full set, with its interactive scenes, is in the Tryals app.

13practice questions
2interactive scenes

Modelling, Moulds and the Workshop