MOULDINGS VIII - THE CYMA RECTA AND THE CYMA REVERSA

In contrast to the simple mouldings covered in previous posts, in which each moulding consists of a single curve, the cyma recta and cyma reversa are examples of compound mouldings: mouldings that consist of two or more curves. In the case of the cyma (from the Greek for ‘wave’) mouldings, there are two curves in each, an ovolo and a cavetto, arranged in series.

The cyma recta consists of an ovolo at the bottom and a cavetto at the top:

In the cyma reversa, the order is reversed, with the cavetto at the bottom and the ovolo at the top:

The cyma recta and cyma reversa are examples of the general group of compound curves known as ogees (pronounced with a soft g), defined as double curves or arcs, one concave and the other convex, joined at a point of inflection, and where the unjoined ends of the curves or arcs point in opposite directions and have parallel tangents; that is, if the ogee curve were in a road you were travelling on, you would be travelling in the same direction upon exiting the curve as you were when entering it. In the recta, the ends extend horizontally; in the reversa, they extend vertically.

In terms of their structural and psychological functions, the recta is a supporting moulding with an ‘upwards’ emphasis, and the reversa is a terminating moulding with an ‘outwards’ emphasis.

The cyma mouldings come in infinite varieties and expressions, depending on whether the curves used are arcs, ellipses, parabolas, or hyperbolas, and on the flatness or depth of the profile. The relative size of each curve in the profile can also be varied; a cyma reversa with a small cavetto topped by a large ovolo, for example, has a much more robust appearance than one with a large cavetto under a small ovolo.

Cymas are typically better employed as the uppermost or lowermost mouldings in a group than they are in an intermediate position. They are almost always combined with small fillets above and below, to isolate and define them against the background planes of the wall or soffit, or against other moulding profiles in the group.

As for remembering the difference between the two, all I could come up with is that the recta resembles a breaking wave, which, if you were surfing it, might mean you were about to get ‘rect’. Not great, but if you have a better mnemonic please let me know!

MOULDINGS VI - THE HOLLOW AND THE SCOTIA

The convex torus covered in the last post has its corresponding concave forms: the simple hollow, and the closely related compound scotia.

The hollow is a concave half-circle; it can also be formed from deeper or shallower arcs or elliptical curves. Its scalloped profile makes it a separating moulding: it produces a strong, smooth shadow gradient, darkest at the top.

The scotia, from the Greek skotia meaning ‘dark, shadowy,’ is a compound curve consisting at its most basic of two arcs, arranged with the smaller radius arc at the top and the larger at the bottom, so that the lower end of the curve ‘runs out’ past the upper end. The two simplest scotia are (1) where the lower arc is twice the radius of the upper, sometimes referred to as the Greek scotia, and (2) where the lower arc is three times the radius of the upper, sometimes referred to as the Roman scotia. Note: you will find different definitions of and formulas for Greek and Roman scotia from different sources; in any case a reasonable generalisation for this and indeed for mouldings in general is that Greek moulding profiles tend to be ‘flatter’ with a sturdier presentation, whereas Roman mouldings are ‘deeper’ and more dramatic.

Bear in mind that these are only the two simplest scotia, and that more complex profiles can be constructed with three, four or even more arcs to achieve a variety of effects.

A two arc 2:1 scotia

A two arc 3:1 scotia

The scotia is often seen at the base of columns, as in the sequence found in the classical Ionic column, which goes, from top to bottom: fillet-torus-fillet-scotia-fillet-smaller torus-plinth. The out-in-out rhythm produces a dynamic effect that is harmonious without being monotonous or repetitive; the separating fillets between the curves give some spine to the composition and prevent it from becoming too ‘soppy.’ Note also the vertical hollows, called flutes, carved into the shaft of the column.

Ionic column base with fluted shaft

MOULDINGS V - THE TORUS AND THE BEAD

Like the ovolo, the torus and the bead are simple convex mouldings, the difference being that where the ovolo is the arc of a quarter-circle, the torus and bead are arcs of semi-circles. They are often flanked above and below by fillets, which give them better definition and prevent the shadows they cast from obscuring the transition from bead to the underlying wall plane.

The distinction between torus and bead, like that between fascia and fillet, is only one of scale: when the profile is thick in relation to the overall composition, it is known as a torus; when thin, it is called a bead (or sometimes an astragal, especially if ornamented). Multiple beads arrayed side by side are known as reeding.

Beads and torii often serve the same auxilliary role as fillets and fascia, and could in fact be considered an extreme kind of ‘rounded fillet’, where the edges of the fillet are radiused to the point that the flat ‘face’ disappears as the rounded edges meet in the middle. The shadow gradient of a torus or bead is a smooth transition from full highlight at the top to full shadow at the base; these profiles produce a richer and more subtle effect than the sharp orthogonal contrasts of the flat-faced fillet and fascia.

Whereas the bead, like the fillet, is considered to be a separating moulding, the wider torus is a binding moulding: it acts to span the elements above and below it rather than severing them.

As convex mouldings, the bead and torus are robust and ‘forward’ in nature, and if over-used or over-sized in a composition can result in a crude or overpowering effect. They are more often seen at the bottom of compositions than at the top, and are usually employed in a supporting rather than a starring role.

A wide fascia topped with a bead is a common choice of profile for skirting boards, and weatherboards beaded along their lower edge can still occasionally be seen on colonial era houses in Australia.

A skirting board consisting of a fascia and bead, separated by a channel (sunk fillet)

The torus is a distinctive feature of the bases of classical columns (the exception being the baseless Doric order), where the bulge of the profile perfectly expresses the work being done by the base of the column in bearing its load, seeming almost to deform in the process. One theory on the origin of the torus in this application is that it represents the ropes once used to tie sacrificial victims to sacred trees, an account that sounds more fanciful than factual.

Two torii at the base of a column

MOULDINGS IV - THE CAVETTO

The cavetto (also known as the hollow or cove) is the concave counterpart of the convex ovolo: both take the form of a quarter-circle arc. But where the projecting mass of the ovolo conveys sturdiness and loadbearing ability, the hollowed-out cavetto is used to express delicacy and lightness, in particular as a crowning moulding (shown above) for ‘topping off’ a building, allowing it to ‘feather out’ at its highest point.

The shadow gradient of the cavetto is the reverse of the ovolo, being darker at the top and lighter at the bottom.  With the sun at 45°, the upper part of a downward-facing cavetto is about ½ shaded, transitioning smoothly to fully lit at the bottom.  The thin, fully-lit fillet that sits on the cavetto in the crowning moulding contrasts with the shaded upper part to bring a sharp definition to the feathered edge of the building.

Whether facing down or up, the cavetto also provides a simple and elegant way of transitioning from a vertical to a horizontal surface; it is still commonly seen in this role, as a plaster cornice covering the joint between wall and ceiling in many contemporary houses. 

MOULDINGS III - THE OVOLO

The ovolo is the simplest of the convex mouldings: its profile is a simple arc, usually of 90 degrees.  The uniform change in angle produces a correspondingly smooth shadow gradient: whether the ovolo faces up or down, the shadow transitions from light at the top to dark at the bottom. 

The convex ‘bulge' of the ovolo gives it a robust, dependable character; whether supporting a cornice or sitting at the base of a column or wall, it expresses a sense of resistance to gravity and muscular deformation under load.

Like the fillet and the fascia, the ovolo is still in common use, chiefly as the small timber moulding known as a quad, which is used to cover joints at 90 degree changes of angle such as that between a external brickwork and the eaves soffit, between a wall and kitchen cabinets, or as cheap skirtings or cornices in utilitarian rooms like toilets or laundries.

MOULDINGS II - THE FILLET & THE FASCIA

After the previous introductory post on mouldings, this and the next several posts in this series will examine the various basic moulding profiles, their uses and effects.

Moulding profiles can be grouped into four general categories: flat, convex, concave, and compound. The fillet and the fascia are the only common flat mouldings; they both present a flat vertical face that may be either raised forward of the supporting wall or sunk into it (then also sometimes called a channel). The distinction between a fillet and a fascia is only one of proportion: the height of the fillet face is typically equal to or only slightly greater than its projection/recess, whereas the fascia is much taller in relation to its projection.

These mouldings produce very sharp shadows. The shadow produced by a sunk fillet is ‘in’ the fillet itself, and is more intense than the shadow produced by a raised fillet, which appears below it. In this case the height of the shadow line varies in proportion to the depth of the fillet projection.

The lighting effects produced by fillets can be modulated in several ways: tilting the face back slightly makes it lighter than the background plane; tilting it forwards darkens the face relative to the plane. Rounding or bevelling the edges of the fillet softens the shading transition at these edges. The top surface of a raised fillet and the bottom surface of a sunk fillet may be given a slight fall, to better shed water and prevent accumulation of dirt.

In classical architecture, fillets and fascia are almost never used in isolation but as auxilliary elements that function to punctuate moulding compositions and define their edges, delineate curves, and give ‘spine’ to the overall composition. When used alone, they can have a stark effect; the sunk fillet in particular was employed to this end by modernists such as Mies to delineate elevator doors and the like.

Though the more complex curved and compound mouldings have mostly fallen out of favour, being perceived as too ornate, too costly or too ‘old-fashioned,' the fascia and the fillet are still in common use, thanks to their simplicity and utility.  The fascia in particular is mostly known today as the timber board used to protect the end grain of projecting rafters and support the eaves gutter, and as the simplest profile of skirting board and architrave.  

Skirting board with fascia profile

Architrave with fascia profile

MOULDINGS I - AN INTRODUCTION

TRADITIONAL BUILDINGS ARE articulate: composed according to an established grammar of parts and joints to form a coherent, hierarchical whole.  One particular characteristic that sets traditional architecture apart from modern, and by which traditional buildings express their articulated nature, is the use of ornamental mouldings: profiles formed in timber, stone or plaster which, when applied according to well-established rules, function to relate the parts of the building to one another through effects of light and shadow. 

From the early 20th century, modern architects, committed to the twin ideologies of social and technological progress, began to reject the ornamental tradition. After a century or more of this process of stripping away, buildings are now for the most part inarticulate, in both senses of the word: they don't have a grammar, and they don't have joints. 

The art of ornamental moulding is no longer taught in architecture schools, but could easily be revived.  There are only a handful of basic moulding profiles, and the rules of thumb governing their use can be found in old textbooks such as this one.

This post will be the first in an irregular series exploring the basic moulding profiles and how they are used, in the hope that it might be of some use to anyone interested in the topic or looking to use mouldings in their own work. Enjoy!

Example illustration from the book ”The Theory of Mouldings” by C. Howard Walker, 1926, linked above.