Polished plaster is a term for the finish of some plasters and for the description of new and updated forms of traditional Italian plaster finishes. The term covers a whole range of decorative plaster finishes, from the very highly polished Venetian plaster and Marmorino to the rugged look of textured polished plasters. [1] Polished plaster itself tends to consist of slaked lime, marble dust, and/or marble chips, which give each plaster its distinctive look. A lime-based polished plaster may contain over 40% of marble powder. [2]
Polished plaster is mainly used internally, on walls and ceilings, [3] to give a finish that looks like polished marble, travertine, or limestone. Such plasters are usually applied over a primer and basecoat base, from one to four layers. They are finished (burnished) with a specialised steel trowel to a smooth glass-like sheen. Polished plaster is usually sealed with a protective layer of wax.
The history of polished plaster can be traced back to ancient times, with evidence of its use in ancient Egyptian, Roman, and Greek architecture. The technique was highly valued for its durability and aesthetic appeal, and it has continued to be used and refined throughout history. [4] [5]
Throughout ancient times, lime was a widely employed material for constructing plaster on both interior and exterior walls. The Greeks, in particular, made a remarkable discovery regarding the production of a special adhesive by subjecting limestone rocks to intense heat within expansive ovens. [6] Nevertheless, this transformative process, which involved converting limestone into calcium oxide, carbon dioxide, and steam, posed significant challenges due to the requirement of extremely high temperatures, reaching approximately 2200 °F. The resulting substance, known as quicklime or lump-lime, was subsequently pulverized into a fine powder and combined with water in a process called "slaking." Through this procedure, a fundamental binding agent called "lime putty" was created and utilized for plastering purposes. The slaked lime, a dense and moist substance, would then be stored in a designated pit for several months, or even years, to ensure complete hydration. Historical accounts suggest that the Romans enforced a regulation stipulating that slaked lime could only be employed if it had aged for a minimum of three years. [7]
Venetian plaster, a distinctive type of wall covering, boasts a rich historical legacy that traces back to ancient times, with its origins linked to Pompeii and the subsequent Roman Empire. Vitruvius, who lived around 80-70 B.C., documented the process of manufacturing lime plaster in his renowned work "De architecture" or "Ten Books of Architecture." [8] [9] These methods were further elaborated upon by Pliny the Elder in his book "Natural History," dating back approximately 2,000 years. The Romans referred to the finished product as "Marmoratum Opus," meaning "smooth marble." The rediscovery of Venetian plaster can be attributed to the Renaissance period, characterized by a renewed interest in the ancient techniques of Rome. Palladio, a renowned Renaissance architect, referred to the process as "Pietra d'Istria" since the plaster bore a striking resemblance to natural rocks such as marble, granite, and travertine commonly found near Venice. Palladio's architectural creations, although seemingly constructed from stone, were in fact composed of brick and stucco. The plastering process involved the initial application of a coarse layer of plaster known as "arricio," followed by subsequent layers of lime putty blended with powdered marble to achieve a smooth and polished surface. On occasion, pigments were added to the wet plaster to introduce vibrant hues.
During the Baroque period, Venetian plaster experienced a decline in popularity, echoing the diminished prominence witnessed after the fall of the Roman Empire. [10] However, in the 1950s, a notable Venetian builder named Carlo Scarpa played a pivotal role in revitalizing the use of Marmorino in contemporary construction.[9] Scarpa not only adhered to the methods outlined by Vitruvius and Palladio but also introduced innovative techniques involving the utilization of animal hides and acrylic resins.
Venetian plaster is a wall and ceiling finish consisting of plaster mixed with marble dust, applied with a spatula or trowel in thin, multiple layers, which are then burnished to create a smooth surface with the illusion of depth and texture. Venetian plaster techniques include marmorino, scagliola, and sgraffito. [11] When left un-burnished, Venetian plaster has a matte finish that is rough and stone-like to the touch. Un-burnished Venetian plaster is also very brittle and damages rather easily.
When applied correctly, Venetian plaster can be used to create a highly polished, rock-hard, marble-like finish. Venetian plaster is especially useful on surfaces where marble panels could not be installed easily, and on surfaces that would be too expensive to have carved from real marble such as columns, corbels, and curved walls.
Venetian plaster can be tinted, or colored using natural or synthetic colorants. The ability to tint Venetian plaster is especially helpful when a specific color of "marble" is desired, or when a color that does not exist naturally is wanted. Through the application of a top layer of wax sealant, Venetian plaster can also be rendered waterproof. [12]
Fresco is a technique of mural painting executed upon freshly laid ("wet") lime plaster. Water is used as the vehicle for the dry-powder pigment to merge with the plaster, and with the setting of the plaster, the painting becomes an integral part of the wall. The word fresco is derived from the Italian adjective fresco meaning "fresh", and may thus be contrasted with fresco-secco or secco mural painting techniques, which are applied to dried plaster, to supplement painting in fresco. The fresco technique has been employed since antiquity and is closely associated with Italian Renaissance painting.
Terrazzo is a composite material, poured in place or precast, which is used for floor and wall treatments. It consists of chips of marble, quartz, granite, glass, or other suitable material, poured with a cementitious binder, polymeric, or a combination of both. Metal strips often divide sections, or changes in color or material in a pattern. Additional chips may be sprinkled atop the mix before it sets. After it is cured it is ground and polished smooth or otherwise finished to produce a uniformly textured surface. "Terrazzo" is also often used to describe any pattern similar to the original terrazzo floors.
Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "render" commonly refers to external applications. The term stucco refers to plasterwork that is worked in some way to produce relief decoration, rather than flat surfaces.
Stucco or render is a construction material made of aggregates, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as a decorative coating for walls and ceilings, exterior walls, and as a sculptural and artistic material in architecture. Stucco can be applied on construction materials such as metal, expanded metal lath, concrete, cinder block, or clay brick and adobe for decorative and structural purposes.
Scagliola is a type of fine plaster used in architecture and sculpture. The same term identifies the technique for producing columns, sculptures, and other architectural elements that resemble inlays in marble. The scagliola technique came into fashion in 17th-century Tuscany as an effective substitute for costly marble inlays, the pietra dura works created for the Medici family in Florence. The use of scagliola declined in the 20th century.
Lath and plaster is a building process used to finish mainly interior dividing walls and ceilings. It consists of narrow strips of wood (laths) which are nailed horizontally across the wall studs or ceiling joists and then coated in plaster. The technique derives from an earlier, more primitive process called wattle and daub.
Lime is an inorganic material composed primarily of calcium oxides and hydroxides, usually calcium oxide and/or calcium hydroxide. It is also the name for calcium oxide which occurs as a product of coal-seam fires and in altered limestone xenoliths in volcanic ejecta. The International Mineralogical Association recognizes lime as a mineral with the chemical formula of CaO. The word lime originates with its earliest use as building mortar and has the sense of sticking or adhering.
Tadelakt is a waterproof plaster surface used in Moroccan architecture to make baths, sinks, water vessels, interior and exterior walls, ceilings, roofs, and floors. It is made from lime plaster, which is rammed, polished, and treated with soap to make it waterproof and water-repellent. Tadelakt is labour-intensive to install, but durable. Since it is applied as a paste, tadelakt has a soft, undulating character, it can form curves, and it is seamless. Pigment can be added to give it any colour, but deep red is traditional. It may have a shiny or matte finish.
Lime plaster is a type of plaster composed of sand, water, and lime, usually non-hydraulic hydrated lime. Ancient lime plaster often contained horse hair for reinforcement and pozzolan additives to reduce the working time.
Plasterwork is construction or ornamentation done with plaster, such as a layer of plaster on an interior or exterior wall structure, or plaster decorative moldings on ceilings or walls. This is also sometimes called pargeting. The process of creating plasterwork, called plastering or rendering, has been used in building construction for centuries. For the art history of three-dimensional plaster, see stucco.
A plasterer is a tradesman or tradesperson who works with plaster, such as forming a layer of plaster on an interior wall or plaster decorative moldings on ceilings or walls. The process of creating plasterwork, called plastering, has been used in building construction for centuries. A plasterer is someone who does a full 4 or 2 years apprenticeship to be fully qualified.
Lime mortar or torching is a masonry mortar composed of lime and an aggregate such as sand, mixed with water. It is one of the oldest known types of mortar, used in ancient Rome and Greece, when it largely replaced the clay and gypsum mortars common to ancient Egyptian construction.
Joint compound is a white powder of primarily gypsum dust mixed with water to form a paste the consistency of cake frosting, which is spread onto drywall and sanded after dry to create a seamless base for paint on walls and ceilings.
Plaster veneer or plaster skim is a construction methodology for surfacing interior walls, by applying a thin layer of plaster over a substrate—typically over specially formulated gypsum board base, similar in nature to drywall.
Marmorino Veneziano is a type of plaster or stucco. It is based on calcium oxide and used for interior and exterior wall decorations. Marmorino plaster can be finished via multiple techniques for a variety of matte, satin, and glossy final effects. It was used as far back as Roman times, but was made popular once more during the Renaissance 500 years ago in Venice.
Faux painting or faux finishing are terms used to describe decorative paint finishes that replicate the appearance of materials such as marble, wood or stone. The term comes from the French word faux, meaning false, as these techniques started as a form of replicating materials such as marble and wood with paint, but has subsequently come to encompass many other decorative finishes for walls and furniture including simulating recognisable textures and surfaces.
Roman concrete, also called opus caementicium, was used in construction in ancient Rome. Like its modern equivalent, Roman concrete was based on a hydraulic-setting cement added to an aggregate.
Cement render or cement plaster is the application of a mortar mix of sand and cement, and water to brick, concrete, stone, or mud brick. It is often textured, colored, or painted after application. It is generally used on exterior walls but can be used to feature an interior wall. Depending on the 'look' required, rendering can be fine or coarse, textured or smooth, natural or colored, pigmented or painted.
Venetian Renaissance architecture began rather later than in Florence, not really before the 1480s, and throughout the period mostly relied on architects imported from elsewhere in Italy. The city was very rich during the period, and prone to fires, so there was a large amount of building going on most of the time, and at least the facades of Venetian buildings were often particularly luxuriantly ornamented.
Qadad or qudad is a waterproof plaster surface, made of a lime plaster treated with slaked lime and oils and fats. The technique is over a thousand years old, with the remains of this early plaster still seen on the standing sluices of the ancient Marib Dam.