An acrylic plinth is a display device that is asked to be invisible. The object floats, the box disappears, and the only thing the visitor sees is the piece and its shadow.
A gallery in Amsterdam commissioned six plinths for a ceramics show. Two bowed under 60 kg stoneware pieces within a month, because the top plate was 8 mm and solvent welded to 8 mm walls with no internal support.
Acrylic plinth load and wall thickness
- 8 mm walls: objects to 30 kg, 900 mm height
- 10 to 12 mm: to 80 kg, with a bonded top plate
- 15 mm or internal frame: heavy stone and bronze
- Top plate: same thickness as walls, bonded on a 5 mm fillet
Load goes through the walls, so a hollow box behaves like a column. The weak point is always the top plate, which spans between walls and deflects. A 12 mm top on a 500 mm span is comfortable; 8 mm is not.
Optical clarity, lighting and the base
Clarity is an edge question. Cast acrylic absorbs a little light per metre and reads green-grey at thickness, so a polished edge and a clean bond line are what make the box disappear. Extruded sheet is clearer but less stable for thick sections.
Internal lighting turns a plinth into a light source. An LED strip at the base washing up the walls works only if the walls are clear and the bond lines are bright; a frosted plinth diffuses into a uniform glow, which suits a translucent object and not a metal one.
The base detail matters for the floor. A 3 mm recess keeps the plinth from rocking on a stone floor, and a felt pad protects the floor finish. Galleries notice both.
Where the plinth sits inside a case rather than in open air, the glazing detail overlaps with museum display case glazing, and the fabrication of thick-walled boxes is covered in acrylic display case manufacturing.
Send your object weight, plinth height and finish to oversales@rpplexiglass.com for a plinth quotation.
Frequently Asked Questions
What thickness acrylic for a plinth?
8 mm walls for objects up to 30 kg, 10 mm to 12 mm up to 80 kg, and 15 mm or an internal frame above that. A hollow box carries load through the walls, so wall thickness is the structural number.
Can a clear acrylic plinth carry a heavy sculpture?
Up to about 80 kg with 12 mm walls and a bonded top plate; beyond that the top plate deflects and the walls are better replaced by a frame under a 15 mm top. Stone sculpture usually needs the frame.
Why do clear plinths look grey?
Edge absorption and dirty joints. Cast acrylic shows a green-grey tint through a metre of thickness, and a poorly bonded top plate shows a dark line. Polished edges and clear bond lines keep the plinth invisible.