La Historia de los Revestimientos: La Civilización Antigua y los Períodos Clásicos

Çatalhöyük fresco,  (ca. 7500 AC)

El arte de hacer revestimientos continuos es tan antiguo como la civilización, de hecho, dicho de un modo más enfático, sin  revestimiento no hay civilización. La habilidad humana de abandonar la cueva, construir su hábitat a base de piedras o cañas y cubrirlo con morteros de tierra, permitió al hombre crear la “cueva” deseada. La construcción de viviendas permanentes cerca del agua dulce y en una posición defendible o contigua a tierras cultivables, significó para la humanidad el inicio de la vida en comunidad y se empezaron a formar las primeras ciudades.

Los primeros revestimientos fueron hechos con tierra. Estos consistían en una sencilla mezcla de arcilla, arena y paja que no necesita fraguar y simplemente se seca con el sol. La misma mezcla se empleaba para hacer ladrillos en moldes. Estas técnicas de construcción con tierra son aún a día de hoy de las más usadas a nivel mundial.

Los revestimientos de calcio, ya sea a base de cal o yeso fueron descubiertos durante la producción de alfarería. Por casualidad, se seleccionaron piedras de yeso y cal para construir el horno donde se cocía la cerámica. El calor del fuego hizo desaparecer el contenido de agua de las piedras de cal y de yeso haciéndolas friables y convirtiéndolas en polvo, cuando el agua se añadía a las brasas para apagar el fuego, se descubrió que el polvo había creado una pasta que endurecía rápidamente.

La Civilización Antigua

Uno de los primeros ejemplos arqueológicos de ambos; de la civilización y de los revestimientos, se encuentra en Çatalhöyük (ca. 7500 AC) todavía presente a dia de hoy en Turquía. Se trata de un denso conjunto urbano hecho con ladrillos de barro, los suelos y las paredes están revestidas con el material del suelo local; una marga arcillosa que sirvió para hacer un revestimiento adecuado. Lo poco que sabemos de esta civilización antigua sobrevive en los frescos pintados representando numerosas escenas de caza, volcanes y patrones geométricos a modo de pura expresión decorativa.

Nefertiti

Los mejores ejemplos de revestimientos del Periodo  Preclásico se encuentran en la monumental arquitectura del antiguo Egipto con fecha del 3er milenio AC. Estas construcciones incluyen las pirámides de Giza hechas con  morteros de yeso y cal, y con revestimientos exteriores acabados con uno fino estuco de cal. Innumerables trabajos de frescos y ornamentos permanecen, así como el renombrado  busto de Nefertiti hecho con yeso que demuestra el paralelo desarrollo artístico de revestimientos decorativos. De hecho, la cal y el yeso producidos en Egipto fueron en muchos casos de calidad superior a la que se encuentra comercialmente hoy en día. Esto nos da el testimonio del hecho empírico de que la producción material de revestimiento refinados empezó muchas generaciones atrás.

La civilización Minoica emergió en el 2º milenio AC en la isla del Mediterráneo de Creta. Los minoicos fueron enormemente influenciados por los todavía exitosos Egipcios, como evidencia  arquitectónica está el Palacio de Cnosos y El palacio Festos.

Aun así, los minoicos fueron distinguidos por su extensivo uso de revestimientos en los espacios interiores. A comparación de los motivos egipcios elaborados en seco, los minoicos hicieron exuberantes y coloridas decoraciones al fresco. Aun manteniendo la vista de perfil y el contorno típico del arte egipcio, las técnicas del buon fresco empleadas por los artesanos minoicos obligó a una manera más rápida e improvisada de trabajar, resultando así una estética más fluida y vibrante.

El Período Clásico

Los micénicos reemplazaron a los minoicos y se convirtieron en la cultura dominante de Creta y del archipiélago griego manteniendo y refinando el estilo arquitectónico Minoico.

Aun así, Roma, caería por siglos a manos de los bárbaros sumergiendo a Europa en los años oscuros. Micenas, tuvo un destino similar a manos de las tribus conquistadoras Dóricas y Jónicas. Durante los años oscuros griegos se perdieron muchos conocimientos de la construcción y de la arquitectura  adquiridos durante siglos.

Finalmente, en siglo 8 AC, los dos grupos rivales se unieron para formar el pueblo Heleno y establecieron su cultura, la cual ha dejado un imborrable rastro en nuestra civilización humana.

Aunque el uso del revestimiento nunca cesó por completo, estos también tuvieron un renacimiento durante la Grecia Helénica. Gracias a los griegos tenemos la palabra Española “yeso”, derivada directamente de "gypsos" (γύψος) en griego. Del mismo modo, es fácil ver la correlación entre nuestra palabra "emplastar" con "emplastron" (εμπλαστρον) en griego, que significa "embadurnar con masa”.

Más allá del legado de la deuda de vocabulario griego, debemos también el mismo fundamento para nuestro patrimonio arquitectónico occidental. La máxima expresión de ornamentación y la representación de los órdenes arquitectónicos griegas: los dórico, jónico y corintio, continúa siendo hoy en día realizada en yeso.

Los griegos fueron invadidos militarmente por los romanos en el s.146 AC. Rápidamente, los romanos fueron simultáneamente cautivados por la cultura griega y adaptándola e incorporando a su filosofía, arte y arquitectura. Los romanos continuaron con su tradición de arquitectura templo; aun así, extendieron su arquitectura monumental para incluir basílicas seculares, monumentos imperiales y villas de palacio. La Domus Aurea “Casa de Oro” del Emperador Nerón y descubrimientos similares en Pompeya y Herculaneum son buenos ejemplos de cómo los revestimientos con cal trajeron el artístico cenit para la élite romana. Estos lugares ofrecen entrever el pasado, una era de opulencia, de lujosos interiores realizados con revestimientos finos muy decorativos, habitaciones enteras pintadas al fresco y bóvedas de cañón conferidas con suntuosas ornamentaciones en bajo
relieve.

Pompeiian Thermae

Los Romanos trajeron no solo grandes artistas y arquitectos, sino que también formidables ingenieros. Un tesoro permanece para nosotros; el exhaustivo tratado arquitectónico, Architectura, datado del siglo 1.AC escrito por el militar Marcus Polio Vitruvius. En su trabajo, conocido comúnmente como Los de libros de Arquitectura, Vitruvio dedica tres capítulos del libro II , para la selección de arena, cal y puzolanas para trabajos de estucos y hormigón. Además, dedicó la mayoría del libro VII a la específica preparación y aplicación de estucos de cal y pinturas al fresco.

La mayor de las civilizaciones antiguas, coincidió con el mejor desarrollo y entendimiento a la hora de hacer revestimientos. Los romanos expandieron el conocimiento más allá de los descubrimientos de los griegos: La adición de puzolanas a la cal, crearía una mezcla que fraguaba en el agua. El cemento nació a la vez que la ingeniería de la construcción estaba en crecimiento y los romanos
empezaron a construir carreteras, acueductos y puertos que todavía perduran a día de hoy. La destreza de la ingeniería romana y el descubrimiento del hormigón, culminó con su incomparable éxito arquitectónico; el Panteón. El cual permanece, siendo el domo más grande de hormigón sin reforzar que jamás se haya construido, con un diámetro interior de 142 metros a su base.

El Panteón, Roma

El tratado de Vitruvio, empezó a alcanzar su amplia publicación a principios del s.15. A finales del s.15 hay evidencia arquitectónica y escrita de las recetas de Vitruvio aplicadas en estuco hidráulico en Venecia y murano, 300 años antes de la llegada del cemento moderno. Más tarde vamos a explorar cómo sus escritos, así como los descubrimientos arqueológicos del Domus Aurea, inspiró a genios creativos como Da Vinci, Michelangelo y Raffaello al alcanzar alturas vertiginosas de la expresión
artística en fresco y estuco labrado durante el Renacimiento italiano.



Escrito por Patrick Webb

Traducido por Anna Castilla Vila

Architectural Word of the Day; 91 - 100

NARTHEX

Placed at the western end of the basilica, the ‘narthex’ is a vestibule screened or walled off from the nave. A covered exterior portico might be considered an exonarthex. Historically, in church architecture the narthex was considered a public receiving area whilst the nave was reserved for baptized members of the congregation.

PINECONE, PINEAPPLE

The stylized forms of the pinecone or pineapple oft serve as decorative finials adorning gate-piers and are a symbol of hospitality. This lichen covered one looks ripe enough to eat!







SERLIANA, PALLADIAN or VENETIAN WINDOW

The use of a semicircular arch flanked by two narrower and lower rectangular openings was revived in practice by Renaissance architects Bramante and Rafael from ancient examples dating to the reign of Roman emperor Hadrian.

However, this motif would gain wide acceptance due to the treatises of Serlio and Palladio, featuring prominently in the later Georgian and Colonial architecture of Great Britain and subsequent Federal architecture of the United States.

Image courtesy of Domiane Forte

AARON'S ROD, CADUCEUS

The Latin term we use today really derives from the Greek karukeion (καρύκειον), meaning ‘herald’s staff’. You may recall it being held by the winged foot Hermes, Greek messenger of the gods. In the Olympic games the eternal flame is kept alive by the herald running with the caduceus, less the serpents and wings.

Of course the caduceus is also a symbol of medicine which may seem strange to us today. However, the association comes from ancient Egypt where before the general domestication of house cats, non-venomous snakes were maintained indoors to keep the rodent population in check and reduce pestilence.

SOFFIT

From the Italian ‘soffitto’ meaning something ‘affixed under’, soffits can refer to the underside of a variety of projecting or transversing features from arches to balconies.

The underneath of projecting cornices are ideal places to enrich mouldings as exemplified by this exterior soffit at the Breakers, Newport RI.

SYMMETRY

Derived from the ancient Greek ‘summetria’ (συμμετρία), meaning ‘of like measure’.

I think bilateral, axial symmetry is easy for us to identify, such as the symmetry we see everyday looking at our own face in the mirror (most of us anyway!) The Breakers in Newport displays this obvious symmetry as well. However, looking more carefully we can find many other subtle examples of symmetry manifest in the proportions of the façade, wing elevations, windows all the way down to the ornamentation.

The Lamp of Beauty – Part II, Monstrosities

Perseus and Medusa, Cellini

Perhaps it sounds odd to set aside a consideration of 'Monstrosities' as a focal point of a larger description of Beauty. Nevertheless, that is precisely what John Ruskin did and with good reason. Ruskin firmly held the position that the purest sources of beauty were "derived chiefly from the external appearances of organic nature." With its practically infinite degree of variety, nature remains an inexhaustible fountain of inspiration. Nevertheless, during the Renaissance there arose a growing tendency to instead conventionalize, to recycle previous forms of decoration as well as to imitate artificial, man-made forms.

By the 19th century the dearth of originality was palpable. Craftsmen were increasingly debased to skilled laborers, simply executing specifications received from architects, drawn from pattern books. Granted, to our 21st century eyes much of this ornamental work was of high quality, still being made from heritage materials, using traditional techniques, produced by the human hand. However, Ruskin and his contemporaries were very sensitive to the direction the Decorative Arts were heading as he expressed, "There are many forms of so called decoration in architecture...I have no hesitation in asserting to be not ornament at all, but to be ugly things, the expense of which ought to be in truth to be set down in the architect's contract, as 'For Monstrification.'"

I'll attempt to highlight some examples of what Ruskin saw as abuses of the period and in his spirit, temper the 'monstrosities' with some healthy examples.

The Meander

Bismuth

Also known as the Greek Key or Fret the Meander was an ubiquitous motif of the Greek Revival period, forged into ornamental iron gates or carved into large friezes and plinth blocks. Ruskin points out that the meander pattern is exceedingly rare in nature, only known to be occurring with the cooling of molten bismuth, itself a rare metal that must first be extracted from bismuth ore. Nature by and large abhors straight lines, particularly at the human scale. Perhaps fitting as a texture at the scale of coins or jewelry, in Ruskin's judgement the meander as architectural ornamentation was just ugly.

The Portcullis

Christ's College Gatehouse

Another contention of Ruskin was that our creation of beauty is owing to an imitative dependence on nature. This wasn't to say that everything a craftman created was a direct, faithful copy of what he saw. To the contrary it might instead be a coincidental resemblance, the incorporation of a particular curve or pattern from a leaf or web into the craftsman's design. Worse than the unimitative, abstract works like the aforementioned meander, Ruskin abhorred artificial imitation of man made objects. The regular grid of the portcullis he described as "unmitigatedly frightful" contrasting it with the worthy subject of a cobweb or wing of an insect.

Tiffany & Co.

Heraldry

Charlton House

Regarding coats of arms and escutcheons Ruskin acknowledged that heraldic decoration has its place, typically a prominent place above gates, entry doors etc. Also, some of the sculpted forms contained within such as animals or flowers might be in themselves quite beautiful. However, he likewise cautioned, "For the most part, heraldic similitudes and arrangements are so professedly and pointedly unnatural, that it would be difficult to invent anything uglier; and the use of them as a repeated decoration will utterly destroy both the power and beauty of any building...it is right to tell those who enter your doors that you are such a one, and of such a rank; but to tell them again and again, wherever they turn, becomes soon impertinence." 

Scrolls and Inscriptions

Perugino's Angels

Similar to heraldry there should be purpose and meaning when writing is introduced into a composition. Neither the writing itself nor the scroll it is written on are natural or inherently beautiful things. This point was lost on many artists who treated the scroll and text ornamentally, often to the point of illegibility as Ruskin elucidates: "All letters are frightful things, and to be endured only upon occasion; that is to say, in places where the sense of the inscription is of more importance than the external ornament. Inscriptions in churches, in rooms, and on pictures are often desirable, but they are not to be considered architectural or pictorial ornaments: they are, on the contrary, obstinate offences to the eye, not to be suffered except when their intellectual office introduces them."

Ribands

Tapeworm

Till now we've considered the scale, appropriateness, in general terms the judicious use of decoration that is not inherently beautiful. Subsequently I'll declare to an outright condemnation. I share Ruskin's view that ribbons, sometimes referred to in an architectural context as ribands, are irredeemably monstrous. They are the flattest, limpest most dead thing introduced into ornament. The closest resemblance to a decorative ribbon in nature is the tapeworm. I have a colleague, an ornamental carver of significant talent, who has produced a number of beautiful works. He also sculpts a lot of ribands. He should stop. They are a sallow stain on an otherwise vibrant portfolio. Honestly, if he receives a commission featuring ribands from an architect he would be better to politely decline or at the very least insist that he be in no way credited or associated with the work.

Stylized Tapeworm

Ruskin's critique is as follows, "Is there anything like ribands in nature? It might be thought that grass and seaweed afforded apologetic types. They do not. There is a wide difference between their structure and that of a riband. They have a skeleton, an anatomy, a central rib, or fibre, or framework of some kind or another, which has a beginning and an end, a root and head, and whose make and strength affect every direction of their motion, and every line of their form. The loosest weed that drifts and waves under the types. heaving of the sea, or hangs heavily on the brown and slippery shore, has a marked strength, structure, elasticity, gradation of substance; its extremities are more finely fibred than its centre, its centre than its root: every fork of its ramification is measured and proportioned; every wave of its languid lines is lovely. It has its allotted size, and place, and function; it is a specific creature. What is there like this in a riband? It has no structure: it is a succession of cut threads all alike; it has no skeleton, no make, no form, no size, no will of its own. You cut it and crush it into what you will. It has no strength, no languor. It cannot fall into a single graceful form. It cannot wave, in the true sense, but only flutter: it cannot bend, in the true sense, but only turn and be wrinkled. It is a vile thing; it spoils all that is near its wretched film of an existence."

Drapery

Apollo and Daphne, Bernini

Like the riband, used in isolation drapery is always ignoble. Unfortunately, it is all too often encountered unceremoniously glued on a blank wall as a decorative swag or littering the urns of every cemetery, desecrating the deceased with a daub of ugliness. However, unlike the riband, drapery finds redemption. Upon the human form it wields the power to convey dynamic forces in motion as well as the static exercise of gravity in repose. Bernini was a master of the former, utilizing drapery to animate his work, Michelangelo the latter heightening the heavy weight of repose. What it lacks in beauty it is capable of conveying in sublimity.

Moses, Michelangelo

The Festoon

The festoon is such a strange, oft displaced creature. Perhaps the gathering of flowers in stone to lay across a sepulchrum in perpetuity bestows both beauty and merit. The question though is really one of architectural appropriateness. It usually appears in the severest of architecture, at a high elevation unable to be truly appreciated, a lopsided crescent gathering soot. I personally feel this at one of my favourite buildings in Paris, Le Panthéon. As Ruskin observed in a similar instance at St. Paul's in London, the awkward "displaced abundance" of the festoon results in the bare wall appearing "poverty stricken", undermining its sublimity.

In Conclusion

I could go on and bore everyone with Ruskin's view of dripstones employed in the Gothic Revival but I'm sure you've had enough. I'll just conclude by saying that I feel Cellini's Perseus and Medusa shown at the outset is one of the greatest nude statues ever conceived. Perhaps you have guessed the monster by now. No, not the head of the gorgon. Rather the true monster is the strap across Perseus' otherwise bare body with the inscription of the sculptor and the date of his work. Oooh Cellini, how could you?

Thankfully he next post in the series will return to a decidedly more positive topic: The Lamp of Life

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Contributed by Patrick Webb

An Architectural Utopia

2001: A Space Odyssey

Utopia is a 16th century literary invention derived from the Greek οὐ, "not" and τόπος, "place". Owing to an homophonic anomaly most folks think 'Utopia' refers to a 'good place'. Sorry to be the bearer of bad news, that would be an 'Eutopia'. An Utopia in point of fact is "no place" at all. I contend that we are fast approaching a global architectural Utopia, a built environment of "no place" and "no one".

An Aesthetic Cleansing

I just cringe when I hear a designer or architect say they are after a 'clean' look. What does a 'clean' look mean anyway? After all I think very few of us would prefer a 'dirty, unclean' look! 'Clean' is code for a sparse, minimalist design bereft of craft, cleansed of ornament, devoid of the polluting evidence of the human touch. A product of industry, possible only with the precision of the machine. We can practically place a date for when this pogrom against craftmanship began in earnest, January 21st 1910, with Adolph Loos' infamous lecture "Ornament and Crime". Ornament and craft were condemned as unevolved and degenerate relics of a primitive past. A self-proclaimed liberator of the craftsman, Adolf claimed their employ by the privileged was abusive and immoral. A progressive society would free them of their toil:

"We have out-grown ornament, we have struggled through to a state without ornament. Behold, the time is at hand, fulfilment awaits us. Soon the streets of the cities will glow like white walls! Like Zion, the Holy City, the capital of heaven. It is then that fulfilment will have come.”  - Adolf Loos

The foretold aesthetic cleansing arrived, carried to its logical fulfillment. The former craftsman freed from his toil, liberated from his art could now slave as a laborer in the factories supplying the materials of industry or assembling them as a "mechanic" in the field.

A School, a Style, and the Rise of the Machine for Living

Bauhaus Dormitory

In 1919 a "House of Building" or Bauhaus was established in Germany putting Adolph Loos' ideas into practical application. Surprisingly, coursework included fine arts and several years of workshop training under the direction of craftsmen and artists. However, the emphasis was technological, the preparation of designs for mass production by industry, canonized by the adopted slogan of the Bauhaus, "Art into Industry". Industrial efficiency demanded a reductive approach, an extreme simplification and unification of design that realized the elimination of moulding and ornament.

The early efforts of the Bauhaus laid the grounds for an "International Style" unveiled in 1932 at the Museum for Modern Art in Manhattan, NY. What made the this style "international"? It certainly did not embrace the millennia of accumulated cultural traditions of many nations and peoples from across the globe. Commonly held among those various humanistic traditions, man had always been held as the subject of architectural design, the building was to be the objective reality, an outward expression reflecting his inner, spiritual nature. In stark contrast, the International Style enforced the complete extinguishment of any lingering artifacts of  human culture, employing a complete reversal of the traditional thought process of design. The new doctrine dictated that "Form" was to follow only practical "Functions". The building and the attendant practical efficiencies of construction usurped the position of subject, placing people as just one amongst many objects such as chairs, toilets, stairs etc. populating the structure. The International Style might have been more appropriately called the Extranational Style, it reflected an aesthetic beyond the cultural influence of any nation or culture. It was the first step towards a new architecture, a Utopian architecture of "no place" in particular.

Drywall Factory

If the International Style achieved an architecture of "no place", several of its visionaries would envision that the built environment of the future would likewise be an architecture of "no one". Prominent leader of the movement, Le Corbusier, declared the house the "Machine for Living". The military industrial complex in place after World War II quickly adapted itself to the mass production of industrialized construction components. Traditional, simple building assemblies, adapted to local environmental conditions, often furnished and always constructed by local craftsmen were rapidly supplanted by complex, standardized cavity wall building assemblies wholly dependent on mechanical systems designed by engineers. The establishment of international building codes would ensure that those engineered building systems were everywhere to stay.

Progress and Propaganda, The Freedom of Limited Choice

Proposed Clemson Architectural Center
Charleston, SC

There is the prevailing opinion that contemporary architecture is progressive, at least among architects who have been indoctrinated in this philosophy. Examples of progress take many forms: embracing new materials, "green, sustainable" technologies and pursuing bold, unprecedented designs. This is epitomized by the American Institute of Architects annual Progressive Architecture Award. The architectural community pats itself on the back for specifying multimillion dollar complexes utilizing high-embodied energy materials of glass, concrete and metal alloys wholly dependent on mechanical systems burning fossil fuels to function, life expectancy unknown. The architects designing these projects are "International", neither educating themselves locally nor maintaining a practice locally, nor are the highly engineered proprietary building systems they specify locally furnished. Instead, they impose a signature style, free of cultural influence, independent of craft that can be plugged into any major city: New York, London, Beijing, Dubai or ceremoniously dumped in the historic districts of traditional cities such as Rome, Kyoto or Charleston. The envisioned "Utopia" has quickly morphed into a "Dystopic" reality, an alien, uncultured, craftless built environment of "no place" in particular.

Tianjin EcoCity Ecology Museum. Courtesy Steven Holl Architects

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Contributed by Patrick Webb 

Escayola

Foto por Walter Cipriani

Se ha creado la más alta expresión del arte del yesero, perdido y redescubierto. Sin embargo, durante los dos últimos milenios Escayola nunca ha dejado de fascinar ni perder su misterio.

Mitad escultura, mitad ciencia, el proceso sofisticado que da a luz Escayola exige la mente enfocada y la precisión de un químico, las manos de un yesero experimentado y el ojo sutil y sensible de un artista.

Historia

Escayola es elaborado a partir de una secuencia cuidadosamente programada para teñir, para mezclar y para organizar los yesos de imitar el mármol. Los arqueólogos han descubierto que los romanos y los egipcios emplearon métodos, desde hace mucho tiempo olvidado, para imitar el mármol en yeso. Sin embargo, fue en el siglo 16, durante el Renacimiento italiano que las recetas contemporáneas de escayola fueron concebidos y perfeccionados para efectuar complicadas incrustaciones en las superficies de los muebles.

A principios del renacimiento muchos mármoles deseados eran raras o se han agotado. Escayola podría imitar esas mármoles, así como crear colores y patrones que no existían en la naturaleza. El uso de Escayola pronto se expandió a los ornamentos moldeados, fustes de columnas y hasta paredes enteras, un proceso que llegó a ser conocido como Estuco Marmo.

El uso de Estuco Marmo expandió por toda Europa continental y finalmente a Gran Bretaña en el siglo 18. Usos destacados de estuco marmo en Inglaterra incluyen columnas y pilastras en el Palacio de Buckingham y la Casa Syon por Robert Adam. Un avance significativo en la tecnología de yeso se logró a mediados del siglo 19 con el advenimiento de Keen's cement. Keen's prepararon el terreno para un nuevo método para la producción de Escayola llamado Marezzo, conocido en los Estados Unidos como Escayola Americana  debido a su rápida aceptación y el uso prominente de mediados del siglo 18 hasta la gran depresión.

Hay innumerables recetas, en todos los casos propietarias, para los ingredientes y la mezcla de Escayola. Vamos a tratar de sacar la cortina de misterio, al menos parcialmente, con una explicación básica de la fabricación Escayola.

Fabricación

Escayola tradicional se puede hacer in situ o en un banco. El trabajo realizado in situ requiere varias precauciones en la preparación del sustrato. En todos los casos, el ambiente de trabajo debe estar limpio, seco y cálido.

Yeso de París finamente molido se utiliza como el ingrediente principal. Pegamento de la piel animal, rico en colágeno, como de conejo o cola de pescado se prepara el día de la fabricación para retardar el yeso y fortalecer el trabajo. Pigmentos minerales secos pueden ser emulsionados en el líquido o mezclados directamente con el yeso seco o incluso introducirse directamente en la masa en función de efecto deseado. Los ingredientes opcionales incluyen yeso o cal molido como material de carga, el aceite de linaza para complementar el pegamento como retardador y para ayudar la manejabilidad, y los pedazos de mármol para ofrecer efectos decorativos.

Al igual que un panadero que maneja la harina, la levadura y el agua, el artesano amasa el yeso de París y el agua colada a la consistencia de una masa firme. Esto se logra mediante la formación de un anillo de yeso seco que rodea a un "castillo" central de yeso. El "foso" se llena con agua colada y el proceso de cortar y amasar comienza.

A través de una serie de cortes, la adición de pigmentos, doblar y amasar, la masa se ​​coloca a un lado como grandes bolas divididas con relación a que logren el resultado deseado: una imitación del mármol verdadero o una creación imaginaria.  Según el resultado deseado, suspensiones de colores y otras preparaciones se reservan para efectos decorativos. Gran parte de la artesanía se encuentra en un proceso de ingeniería inversa mental. Hay que concebir el resultado deseado, tener todos los materiales a la mano y tomar sistemáticamente medidas para lograr el efecto.

Típicamente, el yeso se applica hasta 13 a 16 mm de espesor, dejando 3 mm para el corte de la superficie. Una vez que el material ha alcanzado una fija inicial puede ser afeitado con una herramienta de corte apropiado, tal como un Berthelet Francés, eliminando el exceso de 3 mm a realizar una superficie plana. En este momento el material debe ser todavía maleable y puede dejarse curar como un panel plano. Alternativamente, rebanadas de escayola se pueden presionar en un molde o directamente sobre un sustrato de yeso rayado in situ. Para el trabajo ornamental tales como balaustres, urnas y fustes de columnas, la Escayola se puede girar en un torno.

Una vez que la Escayola se ha permitido para fijar y secar naturalmente el pulido puede comenzar. Tradicionalmente, después de cortar la Escayola, piedra de piedra pómez natural y esponjas húmedas se utilizan para suavizar el trabajo.

El alisado y pulido final históricamente se logró con Agua de Ayr, una piedra natural de Escocia reconocido principalmente como una piedra de afilar para pulir peluquero navajas. Técnicas de pulido modernas llegan a un resultado similar con cada vez más fino papel de lija mojado / seco. La superficie acabada puede ser frotado con aceite de linaza para aumentar el brillo, la dureza y añadir una medida de protección contra las manchas. 

Marezzo o la técnica de "American escayola", fue una verdadera innovación que siguió una metodología distinta. No se requiere un corte de la superficie debido a que el veteado y la coloración se realiza en la cara del molde en una capa fina. Los paneles planos se realizan sobre una placa de vidrio gruesa así que los patrones creados pueden ser vistos desde abajo.

La mezcla de yeso Marezzo se basa en el Keen's cement, un cemento de yeso de lento ajuste que no requiere el uso de retardadores o endurecedores. Hilos de seda se utilizan para vetear y tintes minerales secos pueden ser utilizados para proporcionar color.

Conclusión

Escayola ha disfrutado de una rica historia que adornan muchas de las obras más prestigiosas de Europa, de la arquitectura del Renacimiento hasta el período neoclásico. Asimismo, en los Estados Unidos Marezzo ocupó un lugar destacado en muchas de nuestras obras maestras arquitectónicas del siglo 19 y todavía es de admirar en las grandes entradas de las casas estatales, estaciones de tren y grandes hoteles por todo el país. 


Este artículo fue escrito por Patrick Webb y Sloan Houser
 

Architectural Word of the Day; 81 - 90

APSE

The ‘apse’ is the terminating space beyond the nave at the east end of the basilica. The word derives from Ancient Greek ‘hapsis’ (ἁψίς) meaning arch or vault. It does in fact take the form of a polygonal or a semicircular space covered with a vault or half dome respectively.

The half domes of medieval apses often contained beautiful mosaics, gilding and frescoes. We just recently concluded our annual ‘Spoleto’ festival here in Charleston so I thought it might be nice to show off the beautiful apse from our sister city’s duomo in Spoleto, Umbria.

AEDICULE

‘Aedicule’ literally means ‘little house’ in Latin. It does in fact have the appearance of a miniature temple front, having a small pediment surmounting two pilasters resting on a sill or pedestal.

Often this design is used to give prominence to door entries or as a surround to enrich window openings. Also, it may have a niche that is filled with statuary as depicted here at Palladio’s Teatro Olimpico. 

CLERESTORY

The clerestory is a raised level above the nave, supported by the arcade pierced with windows to bring light and occasionally ventilation into the body of the building.

TRIFORIUM

In some cathedrals there is an additional mezzanine level of arcaded galleries fixed above the principal arcade and under the clerestory called a ‘triforium’, literally meaning ‘three gates’ but having a meaning of ‘thoroughfare’ or ‘passageway’.

I find the elevation at Lichfield Cathedral particularly well designed. There are cinquefoils in the spandrels of the arcade, quatrefoils and trefoils in the traceries of the triforium openings and clerestory windows respectively.

TRANSEPT

‘Transept’ means ‘across the fence’ in Latin. Architecturally it is the section that crosses the nave separating it from the chancel in a cruciform cathedral. Sometimes the division between clergy and laity is literally expressed with a fence as at the Basilica Saint Sernin in Toulouse.

The shared space of the transept and nave is called the crossing and is often surmounted by a dome or spire.

CHANCEL

Also derived from the Latin ‘cancellus’ meaning ‘lattice’ (again referring to the separating fence) the ‘chancel’ is the area beyond the transept that typically holds the choir, presbytery, altar and terminates in the apse.

BASILICA

The Latin ‘Basilica’ originally derived from the Greek (βασιλική) meaning ‘kingly’ or ‘royal’. The Roman Basilica was a public meeting place where business matters could be conducted and sometimes settled by a sitting magistrate, representing the power of the Roman state.

By the 4th century basilicas were being constructed for the church. Over the next few posts we’ll take a look at architectural features typical of basilica architecture.

NAVE

The central body of the basilica, having the highest elevation located just West of the apse. In a church it is usually partially filled with seating for the congregation.

The word ‘nave’ derives from the Latin ‘navis’ meaning ‘ship’ as it was felt the vaulting above somewhat resembled the keel of a ship. I particularly like the labyrinth in the nave of Chartres cathedral. It may not add much architecturally; nevertheless everyone, especially children are drawn to the maze, very interactive! 

AISLE

‘Aisle’ derives from the Latin ‘ala’ meaning ‘wing’. A basilica will often have one or usually two halls running parallel to the nave, the central body of the building. The aisle ceilings are typically lower than the nave.

COMPOUND PIERS, CLUSTERED COLUMNS

A series of large piers form an arcade to separate the aisles from the nave. 16th century engraver, Albrecht Dürer, made some keen observations of the designs of early Romanesque compound piers as well as their evolution manifest in Gothic clustered columns.

Wells Cathedral provides a beautiful example of the unification of the compound piers with the arches and the ribs descending from the vaults above by incorporating aligned colonettes. Although the thrust is obviously downward, the feeling conveyed is vertical and upward as if the arches and ribs ‘spring’ from the capitals of the colonettes.

Contributed by Patrick Webb 

An American Couple’s Perspective on French Wine and Plaster Traditions: Viniculture

Bacchus, circa 1497, Caravaggio

Previously considered was "Viticulture", the cultivation of the grape on the vine itself and its equivalent in plaster manufacture, the careful selection and baking of the various mineral binders. We now progress to our fourth step in the process, "Viniculture", the art of the blend.

At this point, man must utilize his intelligence, engage all of his senses to influence nature. Man as creator of the "Artificial" in the original Latin sense of the word, that which is "made by craft".

Viniculture in Wine 

As we have seen so far, wine making is truly a partnership between the wine maker and nature, with majority control vacillating between one and the other depending on the process underway.  Nature dictates the terroir and the varietals she will support while the wine maker plants and prunes according to those dictates. The partnership story continues now with a look at viniculture, the creative part of wine making; namely hand harvesting, oak barreling and blending as they are practiced by small scale, world-class Bordeaux wineries.

No doubt we’ve seen old photographs of workers manually harvesting grapes from vines and placing them in the small woven baskets on their backs for transport to the winery.  We may look at these photos with a sense of romanticized nostalgia but within them are important, time-tested instructions for the best way to harvest grapes.  Here’s why.

Harvesting begins when the grapes have reached their appropriate sugar to acid balance. Hand harvesting ensures only the best quality grapes are picked and are not damaged in the process. The grapes are then transported in small batches to reduce the risk of being crushed under their own weight.  By using vented baskets, juice from any grapes that are crushed can drain away before it oxidizes and affects the other grapes in the bushel. Once the delicate bundles of juice have been delivered to the winery they are meticulously sorted of any remaining unacceptable grapes and then pressed for fermenting.

What emerges is a wine that is full of promise but whose initial characteristics are often brash and a bit rough around the edges. Centuries of wine making have proven that grapes need time to adjust to their new role as wine and that barrels provide the ideal location for such quiet contemplation.

Through the years various types of wood have been used in barrel making, but oak remains the wood of choice primarily because it contributes the most interesting characteristics.  Oak barrels have their own tannins and are rich in aromatic compounds, which are imparted to the wine. Over time, this interaction tempers the aggressiveness of the new wine while enhancing its flavor subtleties.

Wine blending is another way an artistic wine maker can enhance wine’s subtleties. Contrary to some opinions, wine blends are not inherently inferior to varietal wines. To this point, Bordeaux wines, arguably among the most prestigious wines in the world are blends of several varietals.  In fact, the mighty Cabernet Sauvignon grape itself is a blend of mixed heritage. 

So while less reputable wine makers have been known to blend wines in a “hail-Mary” effort to make drinkable the undrinkable, quality wine makers understand that there is an art to blending and do so only to make minor tweaks to what is already fundamentally good wine.

For instance, a wine maker may decide his Cabernet Sauvignon wine is a bit cloying and bordering on flabby. To provide balance and structure he may blend in a Cabernet Franc wine, which is lighter bodied and higher in acid. Or perhaps a wine perceived to be too crisp, tart and sour, can be muted through blending with earthier, more rounded wines.  Or a wine maker in the enviable position of having several outstanding varietals may select some for blending into an extraordinary and wholly unique wine.

Thanks to high-yielding varietals, fertile soil and industrialized processing, today almost anyone can afford to buy wine; which bottle to bottle, year to year, maintains a standardized flavor profile. Many see this example of technological advancement as a profitable and efficient way for large producers to bring affordable wine to the mass market.  However, quality wine making requires full cooperation of all of our senses; touch, taste, smell, sight, hearing and intuition. For this reason technology, advanced as it may be, will never match the wine maker’s innate human ability to harness, nurture and coax into each glass the sensual essence found in each bottle of wine.

Viniculture in Plaster

Not unlike American choices in wine, "varietal" plasters made from either gypsum, lime or occasionally clay are the norm in the United States. These are largely supplied by industrial manufacturers who modify properties such as the set time, hardness, plasticity of plasters by means of synthetic chemical additives, often with unpredictable and undesirable long term effects. Europeans in general and the  French in particular have a long, continuous tradition of blending the mineral binders themselves to adapt the properties of a resulting plaster to a given use. Fortunately, many of the heritage mineral binders or "varietals" are highly compatible with each other, offering plasters with a wide range of applications, adaptable to almost any specification. Let’s now take a closer look at how this "made to measure" approach of the French utilizes clay, gypsum and lime to prepare the traditional blended plaster, Terre de Séléné.

Ecology. Clay is the primary mineral used for Terre de Séléné plaster. It is a very sustainable choice as suitable clays are widely available and require very little energy to produce. Clay is harvested, left to dry by the sun and goes through a crushing and screening process to make ready for plaster. Like clay, gypsum is also a material that requires little embodied energy to manufacture. Lime requires substantially more energy to produce but fortunately only a small percentage is needed for Terre de Séléné. All three mineral binders are free of volatile organic compounds and completely non-toxic.

Breathability.  Although shared by all three heritage mineral binders, clay has the highest capacity to absorb and release water vapour which can be attributed to its platelet structure, composed of tetrahedral sheets.This property contributes significantly to interior air quality by allowing vapour to migrate naturally through the wall assembly.

Permeability. Gypsum and limes have a loose crystalline structure that allows for the absorption of liquid water. This is a characteristic that all but eliminates condensation inside the wall assembly and absorbs water infiltration from small structural cracks. Yet, permeability can also draw standing water via capillary water rise. However, the aforementioned platelet structure of clay swells as moisture content increases, eventually creating a self sealing effect.

Durability. All three binders imbue Terre de Séléné with high flexural strength, providing incomparable crack resistance, eliminating the need for control joints. Gypsum and lime acts as stabilizers for clay reducing vulnerability to erosion from streaming water. Together with good flashing, water table and eave desgin there are many extant examples of Terre de Séléné that have served their sacrificial function of protecting the substrate for many decades, even centuries.

Efficiency and Frost Resistance.  Gypsum has a rapid set, controllable from mere minutes to several hours. Rapid setting permits subsequent coats to be applied in successive days allowing application to proceed efficiently. This property also becomes very useful for plastering in climates that may undergo freeze thaw cycles within days of application.

Workability and Mold Resistance. Lime has a lower viscosity than clay or gypsum which eases application of the plaster, particularly by trowel. Although mineral binders are inorganic, sometimes organic matter will contaminate the aggregates or water used to make the plaster, providing a food source for molds. The high alkalinity of lime combats the growth of mold during the drying process.

Beauty. Due to the self-binding nature of gypsum, there is a far wider range of flexibility in the selection of aggregates and natural fiber additions than would be available for a clay or lime based plaster varietal. Size, concentration, colour, softness and shape can all be controlled to create a plaster that has a very specific aesthetic. A Terre de Séléné version of "Stuc Pierre", a plaster resembling a limestone or brownstone, is a common composition that reflects the authenticity of traditional, artesanal plasters.

We've spent a good bit of time learning about the Bordeaux wine and Terre de Séléné plaster. Now its time to set the table! The motivation of countless generations of artisans developing these French wines and plasters will next be fully revealed in the upcoming fifth and final segment, the perfect: Pairing.

This article was coauthored by Angela and Patrick Webb