R, S. (rabbit - swags)

Rabbit: (rebate, rabbet) a rectangular sinking along the edge or a piece of material, usually of wood or stone.

Radius: a straight line drawn from the centre to the circumference.

Radius Rod: used to strike/scribe out arches and also gives the length for the gig-stick in running circular mouldings.

Raffling: serrated or notched edges of leaves or foliage.

Reeding: a number of parallel beads.

Relief: prominent sculpted or modelled ornament partly projecting from the background on which it stands.

Relieving Arch: an arch over a lintel.

Render coat: 1: the external plaster system. 2: the first coat of two-coat work (render and set) or of tree-cat work (render, float and set).

Rendering: applying a first coat of coarse stuff to a solid background.

Retarder: an additive which delays the setting of a binder, perhaps to allow more time to work a plaster in its plastic state.

Return: a continuation of a member or moulding in another direction, usually at right angles.

Reveals: the sides of an opening such as a window or doorway between the frames and the face of the wall.

Rims: of casts, the bearing or fixing parts.

Rims: of moulds, the ruling-off edges.

Riven battens, riven laths: formed by splitting rather than sawing the timber. This leaves the fibres intact and gives considerable extra strength compared to sawn timber of a similar size.

Roman cement: the very first quick-setting natural cement was patented by James Parker in 1796. The patent was vigorously exploited and the material was very widely used for fifty years. It has a characteristic warm brown colour. There was production in England, Germany, Russia and the USA.

Ropes: canvas cut into lengths, soaked in plaster, squeezed and twisted to form ropes. Usually placed under laths when reinforcing fibrous plaster casts.

Rose: the round flower placed in the centre of each side of the Corinthian capital; a circular ornament; a flower.

Rules: types used by plasterers; rules backed, buried, eccentric, featheredge, nib, notched, running, ruling in, traversing.

Running a mould: forming a cornice or similar moulding in plasterwork by drawing a template (the running mould) along guides across the plaster.

Running down: this consists of running down short lengths of moulding on either the spot board or a scaffold board, cutting and bedding in position.

Rustic-work, or Rustication: Ashlar masonry with the surface treated in a particular way. There are several varieties; the face of the stone is left rough or is artificially roughened; or it is smooth, but projects and has chamfered or rebated edges.

Sacrificial pointing or rendering: a pointing mortar or render deliberately designed to be less durable than the masonry it protects. Any harmful salts are drawn into its pores and away from the masonry units.

Sand: weathered particles of rocks, usually high I silica, smaller than gravels and larger than silts, typically between about0.06 mm to 5mm. The particles are hard and will not crumble. Sand is used as an aggregate in mortars, plasters and renders as well as a component in concretes. The properties of sand used in a mix have a major effect on its workability, final strength and durability.

Scotia: hollow moulding at the base of a column or pedestal.

Scour, scouring: giving plaster a smooth hard surface by working it in a circular motion with a cross grained float. This draws the binder and finest particles (laitance) to the surface. The same process can actually reduce durability in external work by leaving a lean layer behind the surface, that is a layer with a reduced proportion of binder.

Screed: (in plastering) a carefully levelled band of stuff to act as a guide for the rule, the tool which sets the level of the whole surface.
Scutch hammer: a hammer designed to be fitted with plain or toothed blades which can be replaced when worn out. Used for hacking back grounds to form a key for plaster and render.

Seconds: the second coat of casting plaster used in casting large fibrous casts. It is always retarded and used to brush in all canvas, soaked laths, laps and ropes.

Selenitic: the addition of up to 5 per cent of gypsum plaster to hydraulic lime produces selenitic cement.

Septaria: the petrified excreta of extinct animals, found in nodules in various parts, and used in the manufacture of Roman and similar cements.

Setting: the quality that any material possesses of getting hard in a short time. The term is also used for the finishing coat of plaster work.

Setting stuff: a mix of lime and fine aggregates and possibly gauged with gypsum, for the finishing coat in two- and three-coat lime plasterwork.

Sgraffito: a decorative treatment of plaster achieved by cutting and scratching through a coat of one colour to reveal a different colour in the coat behind. This is done before the plaster has set.

Shellac: a substance made form lac which is a resinous insect secretion. The shellac flakes are soaked in methylated spirits and the solution used to seal plaster surfaces prior to the application of a release agent.

Silver sand: a very fine-grained sand with negligible iron impurities and hence no yellow colour. It has a whitish-grey colour. Sometimes suitable for use in lime plaster finishing coats and lime:sand grouts.

Sisal: a natural material produced from the sisal plant used as a reinforcement and a substitute for hair.

Size (glue size): a glue derived from animal products and used in solution with water to reduce the suction on a porous surface before applying a paint.

Skirting: narrow projecting bunch at the base of a wall.

Slaked lime: calcium hydroxide, Ca(OH)₂. Prepared by hydrating quick-lime in an excess of water to form a milk or putty.

Slaking: 1. Slaking to putty; the actionof combining quicklime with excess water to form milk of lime or lime putty. 2. Slaking to dry hydrate; the action of combining quicklime with the minimum amount of water to form dry hydrate powder. 3. Air slaking: the exposure of quicklime to the air in sufficient quantity to promote hydration.

Soffit: 1: The horizontal lining at the head of an opening. 2. The underside of features such as eaves, arch and stairs, etc.
 

Solid Work: a modern trade term used to distinguish lime or cement plaster work laid on walls or ceiling from fibrous plaster work.

Spandrel: applied to almost any surface of irregular form either plain or enriched; such as the spaces above an arch; between an arch and a cusp; between the ribs of a vault.

Spatterdash: an ordinary Portland cement/sharp sand mix 1:2 prepared to the consistency of a slurry and applied by brush to smooth dense backgrounds to provide a key.

Spinning: the running of circular plastering using a gig-stick and pivot.

Splay: a large chamfer, as to the jamb of a window, etc.

Squinch: an arch built across each angle of a tower to form an octagon to carry a spire.

Staff Bead: a bead at an angle, with a quirk at each side.

Steady up (allow to steady up): allow plaster to take its initial set by drying out to reduce plasticity.

Stilted Arch: an arch of which the springing is above the capital.

Stone lime: a description used before the explicit understanding of hydraulic limes. Sometimes describing hydraulic limes (from greystone chalks) and sometimes fat limes from pure limestone deposits. It was wrongly believed from very early times that the setting strength of a lime depended on the strength of the material from which it was calcined. On that basis limes prepared from marble were believed to be particularly potent.

Stonework: reconstructed; precast ordinary Portland cement/sand features, produced to look like natural stone usually by including crushed rock as part of the aggregate.
Stopping: the filling up and making good small cracks or other defects in plaster or cement work.

Strap Work: ornamentation formed of intertwined flat mouldings.

Strike Offs: the edges on the back of a reverse mould used as grounds when ërulingí off a plaster cast, hence the term striking off.

String Course: a horizontal projecting moulding in a wall.

Stuc, (Stooc): Gypsum plaster and sand used when forming imitation masonry internally, float finish or masonís drag.

Stucco: the Italian for plaster now adopted into the English language and used as a rather smart word to suggest above average quality in an external render, often in imitation of masonry.

Stucco duro: a high quality plastering material based on lime putty, marble dust and fine sands often containing finely ground pozzolanic aggregates.

Suction: the absorption of water by an applied plaster mix.

Swags: festoons of leaves and flowers with drops at each end.
 

Index