What is a rose window?
A rose window is a large circular window whose divisions radiate from the centre, like the petals of a rose or the spokes of a wheel. The pattern is formed by stone tracery, with leaded stained glass in the openings. The rose window is the signature of the Gothic cathedral and almost always occupies fixed positions: the west front above the main portal, and the end walls of the transepts.
Development
It began in the Romanesque period with the oculus: a plain round hole in the wall, undivided. Early Gothic brought plate tracery, in which the openings were cut out of a solid stone slab. High Gothic — the Rayonnant style above all — replaced that with bar tracery: slender moulded stone bars running out from the centre like spokes. That allowed far thinner stonework and far more glass. In late Gothic (Flamboyant) the bars curl in flame-like shapes and the strict radial effect disappears.
| Romanesque: oculus | A plain round hole in the wall, undivided. |
|---|---|
| Early Gothic: plate tracery | Openings cut out of a solid stone slab. |
| High Gothic (Rayonnant): bar tracery | Slender moulded stone bars running out from the centre like spokes; far thinner stonework and far more glass. |
| Late Gothic: Flamboyant | Bars curl in flame-like shapes; the strict radial effect disappears. |
Notre-Dame in Paris shows the sequence clearly: the west rose of about 1225 measures roughly 9.6 metres across, while the later transept roses are close to 13 metres.
Structurally: a large hole in a load-bearing wall
A rose window is a structural challenge — an enormous opening in a wall that has to carry a vault and a roof. Three things make it possible:
- The surrounding ring acts as an arch, turning the load into compression around the opening.
- The tracery carries itself and the glass and resists wind load over the large area.
- Saddle bars. Leaded panels are too flexible for wind load and are supported by slender metal bars behind the glass.
Conservation and maintenance
Rose windows suffer the same defects again and again:
- Rusting iron splits the stone. Historic saddle bars and anchors are wrought iron, drilled into the masonry. Rust expands and forces the stone apart from within; the repair is removal and replacement in stainless steel or bronze.
- Sagging leadwork. Lead fatigues, and over centuries the panels bulge. Repair means taking them out, dismantling and re-leading.
- Weathered mouldings. The slender tracery bars are fully exposed; in sandstone and tuff the profile gradually disappears. New sections are let in bar by bar.
- Secondary glazing is often used to protect historic glass. It is only acceptable with an adequately ventilated cavity, otherwise condensation forms on the inner face of the old glass.
Related terms
- Tracery
- Gothic
- Stained glass
- Rayonnant Gothic
- Rosette
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