Definition
An astragal is a narrow, half‑round convex molding, often resembling a string of beads. In architecture and carpentry it may also refer to a projecting strip used to seal the meeting edge of a folding door or a glazing bar that holds panes of glass together.
Overview
The term is applied in several related contexts:
- Architectural molding – a small, semicircular bead used as a decorative transition between architectural elements such as columns, capitals, or entablatures.
- Door hardware – a thin, beveled strip fixed to the edge of a hinged or folding door to cover the gap between adjoining leaves and improve weather‑tightness.
- Glazing – a narrow wooden or metal bar (often called a “glazing bead”) that secures glass panes within a frame, especially in historic window construction.
Although the primary meaning concerns molding, the word has historically been extended to other objects that share a similar shape, such as certain cannon fittings or dice made from animal ankle bones.
Etymology / Origin
Astragal entered English in the mid‑16th century via French astragale and Latin astragalus. The Latin term derives from Greek ἀστράγαλος (astrágalos), originally denoting the ankle‑bone (talus) of hoofed animals, which was also used to make dice. The Greek word’s ultimate origin is uncertain; some scholars suggest a connection to an Indo‑European root related to “bone,” while others regard it as possibly of substratal origin.
Characteristics
| Aspect | Description |
|---|---|
| Form | Typically a semicircular profile with a radius that gives a bead‑like appearance; may be carved from wood, stone, plaster, or molded from synthetic materials. |
| Size | Varies widely; common dimensions for door astragals are a few millimetres in thickness and height, while decorative architectural astragals may be larger to suit the scale of a building. |
| Material | Historically wood, stone, or plaster; modern production includes PVC, metal, and composite materials. |
| Function | Decorative – adds visual rhythm and articulation to mouldings; practical – seals gaps in doors or windows, enhances weather resistance, and can provide structural support for glazing. |
| Installation | Fixed with nails, screws, adhesives, or mortised into surrounding framing; in doors, the astragal is aligned with the meeting edge and often paired with a sweep or weather‑seal. |
Related Topics
- Bead (architecture) – a similar small convex molding used for decorative purposes.
- Casing and trim – broader categories of finishing woodwork that include astragals.
- Glazing bead – the term used for astragals when applied to window panes.
- Door sweep – a complementary hardware component that works with an astragal to seal door thresholds.
- Astragalus (genus) – a plant genus whose name shares the same Greek root but is unrelated to the molding term.
References – Merriam‑Webster Dictionary, Oxford English Dictionary, and etymological notes from the entry on “astragal” in standard lexicographical sources.