Classical Moldings

Classical moldings are in many ways the building blocks of classical architecture, and there are various aspects to consider when creating them.

First, there are different types of moldings, which can be divided into five categories:

The first category needs no special instructions as they are just vertical planes. The three following categories comprise the bulk of the moldings used in classical architecture (and this work), so will be dealt with below. The last category contains moldings that, except for the scotia (which is used almost exclusively in column bases), are not used much in common classical architecture, and thus will be only briefly dealt with below.

The second thing to consider are the different methods of making the moldings, the choice of which can affect their appearance, which methods include:

The first two are the forms primarily explained below, as they are the most common, as well as the forms preferred by Chambers. On methods of forming moldings he says There are various manners of describing the contour or out-line, of mouldings; the simplest however, and the best, is to form them of quadrants of circles, noting, however, On particular occasions … it may be necessary sometimes to increase and at other times diminish these projections, with the result that moldings may sometimes be made from the summits of equilateral triangles, or be composed of quadrants of the ellypsis.

The complex forms were used by the Greeks and Greek Revivalists, and as stated earlier, will not be discussed here. However, it is worth noting that these type of shapes, as well as those formed freehand, can be replicated using the Bezier tool, as I will discuss below.

Finally, in addition to the different types and shapes, there are different methods for forming them using a computer.

In manual drafting and drawing, the main methods would be through the use of construction lines, circles and arcs, or freehand, relying on your trained eye.

In SketchUp, I have found four main methods to construct them:

The last two methods are ones that will not produce canonical moldings and are thus a matter of personal preference and taste. As a result I will not present those methods here, as you can easily form them from just a picture of the various moldings, and will instead present the ones that will reproduce the canonical forms as shown by various Authorities in their Treatises.

Following are a number of methods I have found described by different Authorities and have interpreted for use in SketchUp. In some cases only one method will be shown, while in others two methods will be supplied, one being a computerized interpretation of the manual steps in drawing the molding, and the other using SketchUp’s built-in abilities (particularly it’s Inference system) to achieve the same result. You can test out whether they are the same by drawing them over each other and comparing how close they are (and then realize how easy SketchUp can make drawing Classical moldings).

In using the instructions below, keep the following in mind:

The Half-Rounds (Torus & Bead)

The torus and bead are almost always formed as a half-circle in Roman and Renaissance work.

To practice the following methods, set a horizontal guide 15 min above the Baseline and another 12 min above that (to simulate the top and bottom of the molding), along with a vertical guide 11 min to the right of the Centerline (for the projection).

Create a Half-Round the Manual Way

a working drawing of this Process.
  1. With the top, bottom & projection of the half-round visible either with guides or lines
  2. Draw a temporary rectangle, as a perfect square, starting from the projection and either top or bottom of the half-round, going diagonally inwards towards the opposite corner
  3. Now draw a half-circle arc, whose startpoint & endpoint are the top and bottom midpoints of the square, and whose bulge is the right midpoint of the square
  4. Erase the square, leaving the half-circle arc

Create a Half-Round the SketchUp Way

a working drawing of this Process.
  1. With the top, bottom & projection of the half-round visible either with guides or lines
  2. Set a guide, going backwards from the projection of the half-round, that is equal to half the height of the molding (to set a midpoint)
  3. Draw an arc, whose start and end points are along the guide just created where it intersects the top and bottom of the half-round, and whose bulge extends to the projection of the molding (forming a half-circle)
  4. Erase the guide set above

The Quarter-Rounds (Ovolo, Cavetto & Congé)

The quarter-round moldings can assume a true, quarter-round form, or one where the height or width is greater, depending on which authority you are following.

The congé I consider a special form of quarter-round as one end will terminate at the endpoint of a vertical surface while the other end will merge into a parallel vertical surface. This is in contrast to the other two quarter-rounds, which abut against vertical or horizontal surfaces at their endpoints. In addition, the congé also connects the cinctures of the column to the actual shaft itself, so their endpoints form the start to the curving entasis of the column shaft.

Create a Congé as a True Quarter-Circle

To practice the following method, set a horizontal guide 3 min above the Baseline (to simulate the top of the cincture the molding will start from), then a vertical guide 30 min to the right of the Centerline, followed by another 4 min to the right of that (for the lower diameter and projection of the cincture).

a working drawing of this Process.
  1. With the beginning and ending of the congé visible as guides, and with the start of the congé visible as an existing fillet or cincture
  2. Set a guide marking the height of the congé (equal to it’s projection), above or below the endpoint of the fillet where the congé is to start (according to whether the congé is going upwards or downwards)
  3. Using the intersecting guides marking the height and projection of the congé as a center, draw a quarter-circle arc, from the endpoint of the fillet out to the edge of the connecting vertical surface
  4. Erase the guide set above

Create a Quarter-Round from Quadrants of Circles the Manual Way

a working drawing of this Process.
  1. Working outside the component, and with a stand-in diagonal line occupying the space in the component where the molding will be drawn
  2. Draw two circles (using 48 sides instead of the default 24 sides for greater accuracy), each centered on one endpoint of the stand-in diagonal line, and with a radius equal to the other endpoint of that same line
  3. Then draw a diagonal line, connecting the intersections of the two circles
  4. Now draw an Arc, whose center is the intersection of the diagonal line and the upper edge of the molding (for the ovolo) or the lower edge of the molding (for the cavetto), with the radius being the endpoints of the diagonal line
  5. Select the arc, cut it into memory, open the component, Paste-in-Place, erase the stand-in diagonal line, and restore the face by drawing over an existing line, then close the component
  6. Erase the construction geometry

Create a Quarter-Round from Quadrants of Circles the SketchUp Way

To practice the following method, create a rectangle 6 1/2 min wide by 6 3/4 min high, with a diagonal line running from the top right down to the bottom left corners, and make all the geometry a group.

a working drawing of this Process.
  1. Working outside the component, and with a stand-in diagonal line occupying the space in the component where the molding will be drawn
  2. Draw a short line extending up from the top of the diagonal line (for the ovolo) or down from the bottom of the diagonal line (for the cavetto), to use with SketchUp’s inference engine
  3. Now draw an arc, starting from the intersection of the short line and the diagonal line, and ending at the opposite end of the diagonal line, and set the bulge such that SketchUp’s inference system shows you the arc is Tangent to the Vertex of the short line
  4. Erase the short line, select the arc, cut it into memory, open the component, Paste-in-Place, erase the stand-in diagonal line, and restore the face by drawing over an existing line, then close the component

Create a Quarter-Round from Equilateral Triangles

a working drawing of this Process.
  1. Working outside the component, and with a stand-in diagonal line occupying the space in the component where the molding will be drawn
  2. Draw two circles (using 48 sides instead of the default 24 sides for greater accuracy), each centered on one endpoint of the stand-in diagonal line, and with a radius equal to the other endpoint of that same line
  3. Draw an arc, it’s center being the outer intersection of the two circles (for the cavetto) or the inner intersection of the two circles (for the ovolo), with the radius being the endpoints of the diagonal line
  4. Select the arc, cut it into memory, open the component, Paste-in-Place, erase the stand-in diagonal line, and restore the face by drawing over an existing line, then close the component
  5. Erase the construction geometry

Create a Quarter-Round from Quadrants of an Ellipse

The S-Curves (Cyma Recta & Cyma Reversa)

The cyma recta and it’s companion molding the cyma reversa are formed of s-curves terminating in flat surfaces.

For the cyma recta those flat surfaces are vertical fillets, so their size is always known.

For the cyma reversa however, the flat surfaces are the underside of the molding itself and the underside of whatever surface is over it (usually a fillet, but sometimes another molding or a form like the corona). For this molding, the size of these flat surfaces (what I refer to as reveals) may or may not be known.

In the case of Chambers, he frequently only gives the dimension for the projection of the molding (i.e. it’s terminating convex curve), so the projection of the reveal (i.e. the space between the molding or element under the cyma reversa and the beginning of it’s concave curve) is not specified. In this case what I do is make the width of the beginning reveal the same as the width of the ending reveal.

The methods shown below present the simplest forms of these moldings, with their two curves being equal in proportion. However, you can vary the appearance by making the curves of different proportions.

When using equilateral triangles, you will draw the construction circles separately for the top and bottom of the cyma curve. Divide the diagonal line into 14 parts, setting the outer circle centered 1 part back from the line endpoint with a radius equal to only 5 parts, and the inner circle centered on the other circle radius, and it’s own radius equal to the other’s center. Then draw your curve arc from the intersection of the two circles, but stretching between all 7 parts of the one half of the divided line. Then repeat this for the other curve.

However, you can vary the shape of the Cyma Curve by dividing the diagonal line into a number of parts and making the construction circles with a radius smaller than half the diagonal line. Palladio shows an example in his First Book, Chapter XXVI, where he divides his diagonal line into 14 parts, and makes the radius of the circles use only 6 of those parts (the centers remaining the same), which produces a more pronounced curve than the standard method.

Just as with the congé, the Cyma Recta molding (and it's companion the Cyma Reversa) can be formed in various ways, of which Chambers prefers that using quadrants of circles.

To practice drawing the cyma reversa, create a rectangle 7 min wide by 7 1/2 min high, with a diagonal line running from the top right down to the bottom left corners, and make all the geometry a group.

To practice drawing the cyma recta, create a rectangle 8 3/4 min square, with a diagonal line running from the top right down to the bottom left corners, and make all the geometry a group.

In the following instructions, when creating the arcs, just remember (so long as moldings are not upside-down) that the cyma reversa is convex on top and concave on bottom, while the cyma recta is the opposite, being concave on top and convex on bottom.

Create A Cyma Recta Or Reversa From Quadrants Of Circles (The Manual Way)

a working drawing of this Process.
  1. Working outside the component, and with a stand-in diagonal line occupying the space in the component where the molding will be drawn, and guides showing the beginning and ending projections
  2. Draw three circles (using 48 sides instead of the default 24 sides for greater accuracy), centered on the two endpoints and the midpoint of the diagonal line, all with a radius equal to half the diagonal line
  3. Then draw a pair of secondary diagonal lines, connecting the intersections of the central circle and the two side circles
  4. Draw a pair of arcs, their centers being where the secondary diagonal lines cross the upper & lower edges of the molding (for the cyma reversa) or the beginning & ending projections (for the cyma recta), stretching from the endpoints of the original diagonal line to the midpoint of that line
  5. Erase the secondary diagonal lines
  6. Select the arcs, cut them into memory, open the component, Paste-in-Place, erase the stand-in diagonal line, and restore the face by drawing over an existing line, then close the component
  7. Erase the construction geometry

Create a Cyma Recta or Reversa from Quadrants of Circles the SketchUp Way

a working drawing of this Process.
  1. Working outside the component, and with a stand-in diagonal line occupying the space in the component where the molding will be drawn
  2. Draw a pair of short lines extending away from the diagonal line, horizontally for the cyma recta or vertically for the cyma reversa, in directions that match the directions the ending arcs will terminate, to make use of SketchUp’s inference engine
  3. Draw a pair of arcs, each starting from the intersections of the diagonal line and corresponding short line, and each terminating in the midpoint of the diagonal line, setting the bulge so it is Tangent at Vertex to the short lines (it should appear cyan blue at this point)
  4. Erase the short lines, select the arcs, cut them into memory, open the component, Paste-in-Place, erase the stand-in diagonal line, and restore the face by drawing over an existing line, then close the component

Create A Cyma Recta Or Reversa using Equilateral Triangles

a working drawing of this Process.
  1. Working outside the component, and with a stand-in diagonal line occupying the space in the component where the molding will be drawn
  2. Draw three circles (using 48 sides instead of the default 24 sides for greater accuracy), centered on the two endpoints and the midpoint of the diagonal line, all with a radius equal to half the diagonal line
  3. Draw a pair of arcs, their centers being the intersections of the three circles, the uppermost & lowermost for the cyma reversa or the sides for the cyma recta, stretching from the endpoints of the original diagonal line to the midpoint of that line
  4. Select the arc, cut it into memory, open the component, Paste-in-Place, erase the stand-in diagonal line, and restore the face by drawing over an existing line, then close the component
  5. Erase the construction geometry

Create a Cyma Recta or Reversa using the Bezier Tool

  1. Working outside the component, and with a stand-in diagonal line occupying the space in the component where the molding will be drawn
  2. Activate the Bezier tool, and select one end of the diagonal line as your start point, and the other end as your end point
  3. Set your first control point (which SketchUp confusingly refers to as “point 2”) along the top or bottom edge (for the cyma reversa) or one side (for the cyma recta) and the second control point (referred to by SketchUp as “point 3”) on the opposite edge
  4. With the form initially set, right-click the Bezier curve, and select Edit Bezier Curve, then carefully select each control point and adjust it’s location. It is a matter of continuous trial and error, adjusting the two points to see how the curve responds, but it allows a greater flexibility than the other methods shown.
  5. When satisfied with the form, select the arc, cut it into memory, open the component, Paste-in-Place, erase the stand-in diagonal line, and restore the face by drawing over an existing line, then close the component

Create a Cyma Reversa from Quadrants of an Ellipse

a working drawing of this Process.
  1. Draw a short horizontal line, starting from the midpoint of the diagonal line, going backwards towards the centerline along the Red Axis
  2. Draw an arc, from the intersection of the short line and the diagonal line, outwards and upwards to the top of the diagonal line, and set the bulge (or curve) so it is Tangent at Vertex (it should appear cyan blue at this point)
  3. Erase the short horizontal line
  4. Now draw another arc, starting at the bottom of the arc just drawn, and ending at the bottom of the diagonal line, with it’s bulge tangent to the arc
  5. Select the two arcs, cut them into memory, open the component, Paste-in-Place, and erase the diagonal line, then restore the face of the component by drawing over a small line, and closing the component

Special Moldings (the Scotia, Thumb Molding, Beak Molding, Three-Quarter-Round & Hollow)

The Scotia Molding

The Scotia is a molding found almost exclusively on Column Bases, and is used to create a shadow effect between a pair of Fillets, frequently separating either Torii or Astragals. The basic shape is a concave curve whose lower endpoint projects farther out than its upper endpoint. The upper endpoint finishes at the edge of a fillet that is usually close to the midpoint of the Torus above it, but sometimes (especially in Greek Architecture) is seen to project farther out than the Torus above, leaving a shadow line between the Fillet and Torus.

There are numerous methods I’ve seen to manually draw the Scotia molding, many of them seeming to depend on the depth and projection of the Scotia curve. I present below several that seem to represent the range from the simplest to the most complex, all with explanations (if needed) to get them to work with the Attic base created above.

The method you choose to form this molding can depend on several factors:

All of the following methods will be presented with instructions that assume the use of the Attic base profile created earlier in this chapter. However, that does not mean that they cannot be used on other forms of base, or that they are all going to actually work with the Attic base. Indeed, in one case some adjustment will have to be done in order to create that scotia version with the profile created above.

Create a Scotia According to William Chambers

a working drawing of this Process.

This method is the one shown in Chambers’ treatise, and also appears in Batty Langley’s Builder’s Director and William Pain’s Builder’s Companion.

This method is drawn using Chambers’ preferred forms derived from quadrants of circles, and is also one of the simplest of the methods to create.

  1. Starting with a component having the fillets above and below the scotia already created, and working outside the component
  2. Draw a line from the bottom-right corner of the upper fillet straight down to the top of the edge forming the lower fillet, then divide this line into 3 parts
  3. Draw a quarter-circle arc, whose center is the bottom endpoint of the top part of the divided line, starting at the bottom of the upper fillet and curving in counter-clockwise towards the Centerline
  4. Select the two lower parts of the divided line and rotate them 90 degrees counter-clockwise away from the Centerline, with its pivot at the bottom of the upper part
  5. Using the center division of the line just rotated as the center, draw a quarter-circle arc, with a radius set to the bottom endpoint of the first arc, counter-clockwise to the edge of the lower fillet
  6. Erase the construction geometry
  7. Select the two arcs, cut them into memory, open the component, and Paste-in-Place
  8. Erase the three straight edges to the left of the pasted curve, then draw a line over the upper fillet projection to recreate the face, then close the component

Create a Scotia According to James Gibbs

a working drawing of this Process.

This method is shown in James Gibbs’ Treatise and is used for all his scotia moldings.

  1. Starting with a component having the fillets above and below the scotia already created, and working outside the component
  2. Draw a line from the bottom-right corner of the upper fillet straight down to the top of the edge forming the lower fillet, then divide this line into 7 parts
  3. Draw a quarter-circle arc, whose center is the bottom endpoint of the third part from the top of the divided line, starting at the bottom of the upper fillet and curving in counter-clockwise towards the Centerline
  4. Select the 4 lower parts of the divided line and rotate them 90 degrees counter-clockwise away from the Centerline, with its pivot at the center of the arc just drawn
  5. Erase the last part on the right of the rotated line, then draw a half-circle construction arc, centered on the new endpoint of this line, starting immediately below it’s center on the lower fillet and going upwards counter-clockwise
  6. Now set a diagonal guide from the top endpoint of the arc just drawn, going downwards and inwards to the center point of the original arc (and with the guide continuing past these two points)
  7. With it’s center using the same center as the first quarter-circle arc, draw another arc, starting from the endpoint of the first arc and going downwards and outwards to the diagonal guide just set
  8. Finally, draw another arc, whose center is the top endpoint of the large half-circle, which starts at the endpoint of the previous arc and ends directly under the center point of this arc on the lower fillet
  9. Erase the construction geometry (the straight lines and half-circle) as well as the diagonal guide
  10. Select the three arcs, cut them into memory, open the component, and Paste-in-Place
  11. Erase the three straight edges to the left of the pasted curve, then draw a line over the upper fillet projection to recreate the face, then close the component

Create a Scotia According to Jacopo Barozzi da Vignola

a working drawing of this Process.

This method is the one shown on Plate 30 of Vignola’s original treatise, next to his drawing of the Attic base.

  1. Starting with a component having the fillets above and below the scotia already created, and working outside the component
  2. Set a guide at the midpoint of the height of the scotia (you can use the rear stand-in line of the scotia to get your midpoint)
  3. Draw a quarter-circle arc, whose center is intersection of the guide just set and the projection of the upper fillet, starting at the bottom of the upper fillet and curving in counter-clockwise towards the Centerline
  4. Draw a line from the bottom endpoint of the arc you just created, downwards to the top right corner of the lower fillet
  5. Using the Protractor tool, set a diagonal guide 90 degrees upwards & outwards from the midpoint of the diagonal line just drawn
  6. Using the intersection of the diagonal guide and the horizontal guide at the bottom of the arc as your center, draw an arc from the bottom of the first arc out to the corner of the lower fillet (the arc will penetrate below the top of the lower fillet, but that is ok)
  7. Draw a line over the top of the lower fillet, so that it breaks the arc just drawn where it passes over the fillet (thus terminating the arc at the fillet surface)

    8. Found evidence this goes below fillet in Greek examples on page 84, Fig 80, of Allan Marquand’s Greek Architecture.

  8. Erase the construction geometry (this including the lower part of the arc and the line just drawn, as well as the diagonal line) as well as the midpoint and diagonal guides
  9. Select the two arcs, cut them into memory, open the component, and Paste-in-Place
  10. Erase the three straight edges to the left of the pasted curve, then draw a line over the upper fillet projection to recreate the face, then close the component

Create a Scotia According to Vignola (via Pierre Esquie)

a working drawing of this Process.

This method is shown in Plate II of the English translation of Vignola by Pierre Esquie. I am not sure what it’s original source it, as it is certainly not in the original edition of Vignola's treatise. Howerver, I present it here as, in the right locations, it can look very nice in my opinion.

  1. Starting with a component having the fillets above and below the scotia already created, and working outside the component
  2. Draw a line from the bottom-right corner of the upper fillet straight down to the top of the lower fillet, then divide this line into 3 parts
  3. Draw a quarter-circle arc, whose center is the bottom endpoint of the top part of the divided line, starting at the bottom of the upper fillet and curving in counter-clockwise towards the Centerline
  4. Select the two lower parts of the divided line and rotate them 90 degrees counter-clockwise away from the Centerline, with its pivot at the bottom of the upper part
  5. Now divide the left part of the rotated line into 3 parts, and then erase the large and 2 small parts on the right side (leaving only the first small part on the left side)
  6. With it’s center at the right endpoint of the remaining line, draw an arc of 45 degrees, starting from the lower endpoint of the original arc, gong counter-clockwise
  7. Draw a line, from the endpoint of the arc just drawn, going upwards and outwards to the center point of that arc (i.e. the right endpoint of the short line), then divide the line into 4 parts, and move/copy the last part at the top upwards and outwards along the same diagonal direction, so you end up with 5 equal parts
  8. Select the 5 parts just created, and move/copy them from the bottom of the arc just drawn outwards and downwards to the top right corner of the bottom fillet
  9. Now rotate the line 45 degrees counter-clockwise so they are vertical on the Blue Axis
  10. Now draw a line connecting the top endpoints of the two lines, then use the Protractor tool to set a guide 90 degrees on the midpoint of the new line
  11. From the intersection of the 90 degree diagonal guide just set and that for the projection of the lower fillet, set a guide going downwards and inwards to the upper end of the diagonal 5 part line so it continues along the same path past the lower fillet
  12. Draw an arc, using the endpoint of the diagonal 5 part line as the center, gong from where this line meets the arc outwards to the first diagonal guide
  13. Finally, using the intersection of the diagonal guides with that for the lower fillet as the center, draw an arc from the endpoint of the arc just drawn down to the lower fillet
  14. Erase the construction geometry as well as the diagonal guides
  15. Select the four arcs, cut them into memory, open the component, and Paste-in-Place
  16. Erase the three straight edges to the left of the pasted curve, then draw a line over the upper fillet projection to recreate the face, then close the component

Create a Scotia ‘By Eye’ Using the Bezier Tool

a working drawing of this Process.

As an alternative to using adaptations of manual methods, you can use the Bezier tool to freely manipulate the curves of your Scotia molding using the steps below.

  1. Starting with a component having the fillets above and below the scotia already created, and working outside the component
  2. Activate the Bezier tool, and set your start point at the bottom right corner of the upper fillet and your end point at the top right corner of the lower fillet
  3. Set your your first control point behind the startpoint along the bottom of the upper fillet, and your second control point directly underneath the first along the top of the lower fillet
  4. Now check the shape of the resulting curve, and if you want to change it then right-click on the curve and choose Edit Bezier Curve, and adjust position of the control points backwards and forwards till you achieve a look that satisfies you
  5. Select the arc, cut it into memory, open the component, and Paste-in-Place
  6. Erase the three straight edges to the left of the pasted curve, then draw a line over the upper fillet projection to recreate the face, then close the component

The Beak Molding