Decorative Plastering

Students at the
American College of the Building Arts

Without question the craft of plastering has always held widespread practical utilitarian value to our built environment. Stuccoes rendered in exterior provide a sacrificial function, protecting vulnerable substrates from erosion and water damage. Plaster applied inside insulates, attenuates sound and provides a sanitary, durable wall surface. Extrusions of profiles in plaster create mouldings that add architectural interest, helping to delineate space by means of shade and shadow. However, among the many craft specializations of the Decorative and Applied Arts, plaster is by far one of the most expressive mediums. We'll take a quick overview of the Art of plastering via some of the traditions still practiced in Decorative Plastering.

Color and Texture

Clay plaster with osyter shells

Fortunately, two of the most commonly used minerals to produce plaster, lime and gypsum, are inherently very white and accept color readily. A few clays are also a light grey and can be tinted to produce a broad, if muted range of colors. Other clays are naturally occurring in a variety of earthen colors such as sienna, umber and ochre that most of us love just as they are.

Marmorino, meaning "little marble", is an Italian tradition of integral colored lime putty plastering inherited from the ancient Romans. Enjoying a 20th century Rensaissance in the Veneto it soon was popularized once again in Italy and now throughout the world.

The French have there own long standing tradition of adding colors and aggregates to plaster. The French plaster is based on gypsum which is naturally more matte than lime. So, instead of marble  the French tradition emulates limestone, called Stuc Pierre, meaning "Stone Stucco". The surface of Stuc Piere is typically shaved with a "Berthelet", a hand held plaster razor, and often scored to create joints in imitation of ashlar masonry. Virtually every culture has developed its own artistic flare using color and texture with plaster: Shikkui in Japan, Tadelakt in Morocco, Enjarre in Mexico to name a few additional examples.


Ornamentation

Moroccan "gebs" or Gypseries

There are two principal approaches to creating ornamentation in plaster. The first is reductive. Morocco has cultivated master artisans of  "gebs", otherwise known as Gypserie, a wonderful tradition of carving into gypsum plaster that is very akin to wood carving, using similar chisels and gouges.

A more widespread reductive method applied to a variety of different plasters around the world is Sgraffito, carving plaster in very low relief. Sgraffito relies on contrast of color between plaster layers for the effect and is a relatively inexpensive way to add a lot of visual punch.

Of course there are the additive forms of ornamentation for which plaster is famous. The finest ornamented stucco is done by hand, in situ. Lime is the preferred medium although sometimes a quantity of gypsum is added to speed up the work and create higher relief. The most awe inspiring work left by the ancient Romans and emulated in the Renaissance was all painstakingly carried out by hand by armies of sculptors. These must have been very exciting times to be a plasterer! As mold making technologies increased in the 18th century, in situ ornamentation became largely displaced by pre-cast ornamentation in gypsum plaster. Gypsum has a rapid set, just a few minutes, so once time has been invested in a master model, many copies can be made quickly.

Enrico Trolese, contemporary Venetian Stuccotoro

Scagliola and Buon Fresco

There are a few really special applications of decorative plastering that could easily take a lifetime to master. One of those is Scagliola. Scagliola is a technique of emulating marble, typically with gypsum plaster. The artistry required is tremendous. Just matching colors as they occur in marble or developing your own color palate is a challenge in itself. As the technique requires cutting, folding and stacking loaves of plaster in various orientations repeatedly, you must continually visualize what is happening inside, how all of those layers are coming together in a natural way, recreating the subtle variegation of color, veining, stratification and fracturing that occur in marble are all separate skills.

Perhaps the highest artistic expression of plaster, one that blurs the line Buon Fresco. Painting mineral pigments into lime plaster while it is still fresh takes incredible understanding of materials. The plaster must be prepared in a way so that it maintains a consistent level of dampness for as long as possible. Fresco can be as simple as brushing two or three coats of a mineral wash into a completed wall to give it a soft, cloudy, parchment effect to most elaborate works of fine art and trompe-l’œil.

What is important to recall about all of these various decorative plastering traditions is that many of them can and are used in combination. Scagliola might be pressed into moulds to make ornamental pieces that resemble carved marble. Marmorino or a similar fine lime putty plaster is the grounds for painting Buon Fresco.

The art of plastering really has not changed much in thousands of years. We use the same commonly available materials and techniques we always have. And although to become truly expert at the various arts of decorative plaster requires patience and practice, the truth is they are quite humanistic endeavors, appreciable and accessible to most everyone.



Contributed by Patrick Webb

Architectural Word of the Day; 21 - 30

Sketch courtesy of Gary Callahan

EGG & DART

 Carved into the ovolo (half round) profile of stone or wood or cast in plaster or metal, the iconic egg & dart mould enrichment alternates the feminine symbol of fertility, the egg with the male symbol of virility, the dart.

At the Getty Villa

TRANSENNA

The Romans did not employ balusters in the design of their parapets and banisters. Often a 'pierced screen', the Latin 'transenna' was used instead.

Also common for window openings the transenna offers security and privacy whilst providing beauty and air flow.

Photo courtesy of Palladio Mouldings

ANTHEMION, PALMETTE

The Greek ‘anthemion’ (ανθέμιον) meaning ‘flower’ or ‘blossom’ had been an extensively used motif inherited from the Ancient Egyptians, subsequently embraced by the Romans.

The anthemion or palmette was a prominent spiritual symbol of life and renewal often adorning mausoleums and sarcophagi.

 The Wentworth Mansion

 

QUOIN

We’ve adopted the French word for ‘corner’ to describe the external angles in architecture typically emphasized by rustication in stone or stucco. 


ROSETTE

Clearly derived from ‘rose’, the French diminutive version of the word describes most smaller, stylized, round, symmetrical floral or plant ornament.

I love these two plaster rosettes from the Getty Villa, lotus on the left and acanthus on the right.

Courtesy of Steve Shriver

VITRUVIAN SCROLL

Vitruvius may get the credit because this linear band pattern features so prominently in Roman architecture; however, wave scroll designs go back to antiquity. Also called a Running Dog (I never liked that name).

Steve Shriver produces an interesting variation of the pattern freehand as a sgraffito motif in marmorino. 

Photo courtesy of Palladio Mouldings

BRACKET, CONSOLE

A projecting supporting member. Depending on the style and how it is used there are various designations

Modillions and Corbels, like the one depicted in the photo, are characterized by an S-curve whereas other brackets such as the Mutule from the Doric order are angular.




Contributed by Patrick Webb  

Plaster Word of the Day; 11 - 20

ADOBE

The work ‘adobe’ comes directly from Spanish who in turn inherited it from the Arabic ‘al-tob’ (الطوب). The term simply means ‘brick’, having its origins in ancient Egypt as verified by surviving hieroglyphs.

Today ‘adobe’ has a more specific meaning of a sun dried brick formed from clay, sand, water, straw and sometimes having additives such as manure, soil, lime, etc. A similar mixture is used for mortar and as an earthen plaster to bond and protect the adobe bricks.

SCRATCH, BROWN, FINISH

This description of a 3 coat plaster system (usually over lath) is more common in the US and applies to all types of plasters: lime, gypsum, cement etc.

The ‘scratch’ coat is the base layer and as you might guess receives scratches to receive the next coat. It is important that the scratches run horizontal, essentially forming little shelves for the next coat to sit inside and lock into

The ‘brown’ coat is the middle coat. Traditionally either brown sand was used or some mineral tint was added so that the plasterer could easily gauge if he had sufficiently covered the scratch and to make sure he had good coverage when applying the finish.

The ‘finish’ is applied last. Unlike the first two coats where thickness was achieved and the geometry of the wall was established, the finish is typically a thin veneer to create a smooth surface.

Image courtesy of Franco Saladino

MARMORINO

‘Marmorino’ describes an entire system of lime plastering inherited directly from the Romans as recorded by Vitruvius. It enjoyed a vibrant revival during the Renaissance, spreading from the Veneto region, where it had continued as a craft tradition, to the rest of Italy.

The word ‘marmorino’ is the diminutive form of the Italian ‘marmo’, meaning ‘marble’. So ‘marmorino’ has a direct translation something like ‘little marble’. Outside of Venice it has taken on the more specific meaning of the final coats which are rich in lime and taken up to a high polish

Image courtesy of Simple Construct

EARTHEN PLASTER

In discussing Adobe construction a few days ago we mentioned that the bricks traditionally would receive an earthen plaster. Earthen plasters are undoubtedly the oldest form of plastering because no cooking is required. Rather than having a chemical ‘set’ it simply dries out. They are still used in Adobe construction as well as over other natural building substrates such as Straw Bales and Rammed Earth.

The binding component of an earthen plaster is clay, meaning clay is the material that holds the other ingredients (silt, straw, sand etc.) together. A certain percentage of clay is required to make a suitable plaster. Too little and the plaster is weak and friable. Too much and the shrinkage of the clay will lead to cracking.

The image provides a good initial test to see if a site soil has a good percentage of clay or will need to be modified.

FRENCH PLANE

A common tool in the French plastering tradition. Wider versions are used to level wall surfaces whereas the narrow version is the tool of choice for creating faux masonry joints.

The narrow tool is called ‘Chemin de Ferre’ or ‘iron horse’. An appropriate metaphor as the plane has the shape of a train engine and runs along a straight edge or ‘track’.

Image courtesy of Plâtres Vieujot

RUN-IN-SITU

Previously we discussed the running of plaster moulds on a bench to later be affixed. However, a more traditional method is to realize the work on site or ‘in situ’. This type of work is usually referred to as ‘run-in-place’ in the US.

The same mechanical process of running a profile along a track is used for run-in-situ as for bench running; however, the level of skill required is much higher. Instead of using Plaster of Paris which has a rapid set, a common mix is to use lime gauged with gypsum plaster and a small amount of retarder to provide more time to complete the moulding.

Image courtesy of Palladio Mouldings

MODEL

Modeling describes the art of placing enrichments on a moulding in preparation to create a mould. Hence you’ll hear the expression ‘model and mould’ although they are two distinct actions not always performed by the same person.

A good modeler must understand layout well and is responsible for geometric enrichments. However, an experienced modeler will develop at least limited sculptural ability for repeated motifs such as egg-and-darts and acanthus leaves

Image courtesy of Palladio Mouldings

ARCHITECTURAL SCULPTING

There is a distinction made between the responsibilities of the modeler and that of the architectural sculptor. Although still possessing a solid understanding of geometry and precedent in ornamentation, architectural sculpting goes beyond planting repeated motifs on a moulding to embrace free formed, often asymmetrical or unique designs such as cartouches, bas-relief or ornate column capitals such as the Corinthian capital being developed here.

Having been trained classically in figurative study and having worked in mediums as diverse as clay, plaster, wood, stone, the architectural sculptor often assumes the responsibility of art director working with his team of modelers in larger ateliers.      


Contributed by Patrick Webb  

Plaster Word of the Day; 1 - 10

Image courtesy of Plâtres Vieujot

PLASTER

One of the foundations of a good trade education is understanding the vocabulary of that trade. So for a plaster education we’ll begin with the most fundamental of terms, Plaster.

In some languages and localized areas of the English speaking world plaster is ‘mineral specific’, such as a gypsum derived material, or ‘use specific’ such as a coating applied in interior. However, our English word “plaster” ultimately derives from the Greek ‘emplastron’ (εμπλαστρον) meaning “to daub on”.

So the term “plaster” can rightly describe a variety of interior or exterior coatings that are daubed, thrown or trowel applied.


SCREED

Finally we have an English word that has its roots in…English!
Screed is an Old English word that originally meant a strip of cloth but eventually came to mean a strip of anything. In fact, ‘shred’ has the very same etymology.

In plastering it refers to strips serving as a termination and guide for the larger infill areas. Often if wood, metal or non-plaster materials are used it will be referred to as a ‘ground’. However, if the strip is made of plaster it maintains the name screed.

Also, a screed is a generic term for the straight edge used to level the infill surface and the act of leveling is called ‘screeding’. There are a variety of screeds that have specialty applications with names such as rods, darbies, slickers etc.


RENDER, FLOAT, SET

This grouping of vocabulary comes from across the pond, common terminology in the UK and Ireland.

It is most descriptive (but not exclusively) of the traditional 3 coat lime plastering system used over monolithic substrates such as brick or stone.

The RENDER is the first coat of plaster, the ‘coarse stuff’ with large, sharp aggregates. It is applies rough and and gets scratched up to provide a mechanical key or bonding surface for the next coat.

The FLOAT is the next coat with the same material. However, the surface is scoured, compressed and leveled with a wooden hand float, hence the name.

The SET, is the final coat. This is the final mix with lime putty and fine aggregates with Plaster of Paris (gypsum plaster) added to initiate a 'set' or firming up of the lime.


GYPSUM PLASTER

Image courtesy of Plâtres Vieujot

The Greek work ‘gypsos’ (γύψος) described the mineral that we today identify as gypsum.
Gypsum plasters may contain sand and small percentages of other binders such clay or lime.
Many useful gypsum plasters are in fact a blend of different types of gypsum:

Gyp – Pulverized gypsum with the chemical designation hydrated calcium sulphate (CaSO4•2H2O). Often used as a natural accelerator in gypsum plaster.

Beta Gypsum – Gypsum baked at a low temperature to form calcium sulphate hemi-hydrate (CaSO4•~0.5H2O). Also, known as Plaster of Paris.

Alpha Gypsum – The hemi-hydrate form baked under higher barometric pressure. The resulting material can have up to 10 times the compressive strength of beta gypsum.

Anhydrous Gypsum – Gypsum baked at a higher temperature to form pure calcium sulphate (CaSO4). Often used as a natural retarder in gypsum plaster.

BLISTER BRUSH

Also known as a ‘felt brush’ or just a ‘mop’.

This is an effective tool for moisture management when finishing clay, lime or gypsum plasters.

The release of water is directly related to pressure applied. Over-saturated areas common with sponges and pump sprayers are easily avoided with a blister brush.

 
SGRAFITTO

Image courtesy of Plâtres Vieujot

This technique of carving into a plaster to reveal a contrasting colour underneath is very much associated with the Italian tradition from whom we have directly borrowed the word sgrafitto meaning ‘scratched’. However, the Italians in turn had borrowed the term from the Greek ‘gráphein’ (γράφειν) meaning to write.

From the same origins the Germans first coined the common designation for the form of carbon useful for writing, ‘graphite’.

 
BENCH RUNNING

Plaster mouldings can either be formed 'in place' or on a flat table or 'bench' to be later applied.

When formed on a bench typically Plaster of Paris, moulding plaster is used which has a rapid set. You have to move quickly when using pure moulding plaster hence the term 'running'. 


GYPSERIE

The technique of chiseling into fresh plaster in deep relief in situ (called ‘gebs’ in Arabic) is a craft that was developed to perfection by the Moors. After the expulsion of the Moors from the Iberian peninsula Muslim artisans were given opportunity to convert and some continued their craft in Christian motifs developing a very rich tradition in Provence.

Gypsum is the ideal medium for this technique. While fresh gypsum plaster is soft enough to easily carve it has great plasticity and will not easily crumble. This makes it possible to achieve deep undercuts with sharp edges and thin details that soon develops hardness and durability as the plaster dries and fully cures. 


Contributed by Patrick Webb 

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

Château de Chambert

Nature. Culture. Perhaps these seemingly disparate aesthetics were no better reconciled than by the French Renaissance tradition of the formal garden.

“In the Renaissance taste the garden was an extension of the main design. It was a middle term between architecture and Nature. The transition from house to landscape was logically effected by combining at this point formality of design with naturalness of material.” – Geoffrey Scott, The Architecture of Humanism

To this point we have considered Varietals and Terroir…learning about grapes and minerals…exploring soils, weather and geology…recognizing all of nature’s generous contributions. All that we have hitherto discussed is most fundamental; however, wine and plaster are uniquely products of culture. The balance of our five part series will consider the human touch.

Viticulture in Wine

Although located in what is considered the “old world” of wine production, Bordeaux is squarely in the forefront with regard to wine-making technology.  So in this segment we are going to discuss an aspect of the Bordeaux wine industry that receives nowhere near the attention it deserves. We are talking about viticulture. Viti is latin for vine therefore viticulture roughly translates to vine cultivation.  In this article, we will examine two methods of viticulture that are essential to making a great wine; vine manipulation and pest control.

Vine leaves contain chlorophyll cells that absorb sunlight enabling the plant to extract carbon dioxide from the air and convert it to sugar. The nutrients imparted by the sugar feeds the vine roots, grape clusters and leaves ensuring the entire plant receives exactly what it needs, when it is needed.

Allowing too much foliage shields the grapes from the sunlight they need for the last stage of their healthy development, so pruning is crucial to producing a quality wine. However caution must be exercised with cutting, because every cut is an entry point for pests to enter and attack the vine.  On the other hand, if too many leaves are pruned, the plant does not have the means to absorb sufficient sunlight to sustain the entire vine.

Wine grapes emerge at the end of the growing season so the plant’s nutrients must further be shared with the new grape clusters. If there are too many clusters, the sugar and acid levels will likely be undeveloped and/or unbalanced resulting in a poor showing as a wine.  Too few clusters negatively affects potential profits from wine sales.

Pest control is another very important aspect of viticulture. In the 1870s a small, deadly phylloxera louse made it’s way to Europe and all but wiped out all wine production. Phylloxera destroys the grapes, rots the vines and often leaves its larvae in the root, eventually killing the vine completely.  Although Bordeaux and Europe at large have regained their wine producing capabilities, phylloxera and other lice, along with viruses, bacteria, fungi, mites and insects are still among the many threats to healthy vines.

In an effort to eliminate ongoing threats to their vineyards and livelihoods, many late 20^th century wine growers often used chemical fertilizers and pesticides indiscriminately.  Thankfully much has changed since then with most of the region’s winegrowers using more environmentally conscious, natural pest control methods.  For example, Bordeaux wine growers are currently and constantly experimenting with root grafting in order to find the genetic combination that is naturally resistant to harmful bacteria and viruses.  Scientists and wine growers are also experimenting with sea algae as a natural deterrent to gray rot. 

There is no doubt that viticulture is both science and art.  Winemakers must have intimate knowledge of their vineyard’s terroir as well as which viticulture methods will work best within its parameters. It is with this intricate knowledge and dedication to quality that winemakers are able to extract the best wines from the best grapes.

Viticulture in Plaster

France is a geologically, minerally rich country. Correspondingly rich in culture, the French have been very successful in exercising their influence over a number of raw mineral materials to produce some of the finest plasters in the world. The plaster equivalent to Viticulture is baking. Let’s now take a closer look at how 3 minerals are prepared for our blended plaster, Terre de Séléné.

Clay is the primary mineral used for plaster in Terre de Séléné. It is an abundant mineral worldwide, the result of millions of years of erosion. In parts of France a relatively pure form is available just under the topsoil, just a few feet below ground. It is easy to excavate and is still traditionally dried by the sun. Later, with minimal effort, it is ground into a powder ready to be used for plaster. While there are a variety of clays in France, clay with a low shrink-swell capacity such as Kaolinite is desirable for Terre de Séléné.

Historically, the French were enamored with this type of clay for additional uses. The word “Kaolin” comes to us directly from French. They in turn inherited the term from China. In the early 18^th century the French were obtaining an extremely pure form of clay useful for porcelain, “China”, from a deposit near a mountain the Chinese called Kao “high”, Ling “hill”.

Gypsum is the secondary mineral used in Terre de Séléné plaster. Gypsum is plentiful in France and particularly so in Paris. Gypsum plaster is almost synonymous with the expression “Plaster of Paris”. Paris in fact sits on a “massif” or deposit of mineral gypsum that is among the largest and finest in quality on earth. Naturally occurring gypsum is a type of salt that precipitates through cycles of evaporation from lime or other calcium compounds, typically in lagoons or inland seas.

Preparing gypsum plaster requires a little more effort and energy than clay. It is usually mined from underground deposits. Relatively soft as a stone, it is easily pulverized to a coarse sand ideal for baking. Most of the gypsum plaster useful for Terre de Séléné only needs to be baked at under 350° F for less than an hour. In general, considerable influence can be exercised in the baking process. Adjustments to the grind, temperature, length of baking and even barometric pressure can produce an amazing range of properties in gypsum plaster such as fast setting plasters good for casting or extremely dense, hard plasters appropriate for floors or countertops.

Limestone is the third mineral used for our plaster blend. In abundance in the South of France, limestone is a sedimentary stone, the result of millions of years of marine skeletons accumulating on ancient sea beds. The lime most useful for Terre de Séléné plaster is very pure, having little contamination from magnesium or silicates. By itself, limestone is very useful as a building material; however, to produce a plaster requires considerable fuel and labor.

Limestone is found underground but is plentiful and easier to extract from surface mines. Much harder than gypsum or clay, extraction is laborious. For baking limestone is broken into golf ball size pieces. Traditionally, it was baked for 24 hours in vertical kilns at an extremely high temperature of 1500° F. Modern production methods utilizing crushers and horizontal kilns have reduced the time considerably.

The resulting “quick” lime is highly caustic, potentially hazardous to handle. At this point of production enough water is introduced to cause a partial reaction that reduces reactivity and danger. The slaked lime, also known as dry hydrate, is now ready to be blended with the clay and gypsum plaster to make Terre de Séléné.

As you have read, the French traditions of Viticulture and plaster preparation are very sophisticated. The usefulness of our modern scientific, chemical understanding still lags behind the practical experience gained through centuries of empirical observation and practice. This is especially evident in our subsequent, fourth segment considering the art of the blend, Viniculture.

This article was coauthored by Angela and Patrick Webb

The History of Plaster in Classical Architecture: The Ancient and Classical Periods

Çatalhöyük fresco (ca. 7500 BC)

The art of plastering is as old as civilization. In fact, stated more emphatically, without plaster there is no civilization.  Mankind’s ability to leave the cave, raise a shelter of stones or reeds and coat that shelter with an earthen plaster enabled him to create the “cave” wherever he desired. Building permanent dwellings close to fresh water, upon a fortifiable position or adjoining arable land allowed extended families to gather and the first cities to be born.

The very first plasters were earthen. Being simple mixtures of clay, sand and straw they required no furnaces and dried with the sun. The mixture was cast as bricks and the same basic formula was used as the mortar and stucco. Earthen plasters such as cob and daub are still the most commonly used plasters worldwide.

Calcium plasters such as gypsum and lime were likely discovered through the process of pottery making. By chance, rocks of gypsum or lime were selected to form the crude kiln for firing pottery. The heat of the fire drove off water (gypsum) or carbon dioxide (lime) leaving friable rocks quickly falling to powder. With water thrown on the embers to quench the fire it was soon discovered that this powder formed a paste that quickly hardened.

The Ancient World

One of the earliest archeological examples of both civilization and plaster is that of Çatalhöyük (ca. 7500 BC) located in present day Turkey. A densely populated town, Çatalhöyük‘s dwellings had mud brick walls and floors coated with a locally available clayey marl that made a suitable plaster. What little we know of this ancient civilization survives in lime frescoes depicting numerous scenes of hunting, volcanoes and geometric patterns of purely decorative expression.

Nefertiti

The best preserved examples of plasterwork in the pre-Classical period are found in the monumental architecture of ancient Egypt dating from the 3^rd millennium BC.  Practical construction uses include the pyramids of Giza containing gypsum and lime mortars, the exteriors of which originally received smooth lime stucco. Countless surviving works of frescoes and ornament such as the renowned gypsum bust of Nefertiti attest to the parallel artistic development of plasterwork. In fact, the lime and gypsum plasters produced in Egypt were in many cases of superior quality than commercially available today. This gives testament to the fact that the empirical refinement of plaster manufacture extended many generations further back in time.

The Minoan civilization emerged in the 2^nd millennium BC on the Mediterranean isle of Crete. The Minoans were greatly influenced by the still flourishing Egyptian culture as evidenced by the architecture of the palaces at Knossos and Phaistos. However, the Minoans were to distinguish themselves by the extensive use of plaster in their interiors. In contrast to formalized Egyptian motifs typically carried out al secco, the Minoans had an exuberance of colored decoration realized al fresco. Although maintaining the profile view and stark outline typical of Egyptian art, the buon fresco techniques employed by Minoan artisans obligated a faster pace and improvisation resulting in a fluid, vibrant aesthetic.

The Classical Period

The Mycenaeans would succeed as the dominant culture of Crete and the Greek archipelago maintaining and refining the Minoan architectural style. However, as Rome would fall centuries later to the barbarians plunging Europe into a Dark Age, a similar fate befell Mycenae primarily at the hands of the Dorian and Ionian conquering tribes. During this Greek Dark Age much of the knowledge of construction and architecture was lost for a period of centuries. Finally, in the 8^th century BC, the two rival groups would join to form the Hellenes and establish a culture that left an indelible mark on human civilization.

Although the use of plaster never ceased entirely, it too would experience a renaissance in Hellenic Greece. Thanks to the Greeks we have the English word “gypsum”, directly derived from the Greek gypsos (γύψος). Similarly, it is easy to see the correlation between our word “plaster” with the Greek emplastron (εμπλαστρον) meaning “to daub on”. Beyond our debt of vocabulary, we owe the very foundation of our Western architectural heritage to the Greeks. The highest expression of ornament and representation of the Doric, Ionic and Corinthian Greek architectural orders to this day continues to be realized in plaster.

The Greeks were conquered militarily by the Romans in 146 BC. Yet culturally the Romans were simultaneously enthralled by Greek culture adopting and incorporating their philosophy, architecture and art. The Romans continued the tradition of temple architecture; however, they extended their monumental architecture to include secular basilicas, imperial monuments and palatial villas. Emperor Nero’s Domus Aurea or “Golden House” and similar discoveries in Pompeii and Herculaneum are well preserved examples of how lime plastering was brought to an artistic zenith for the Roman elite. These sites offer a glimpse into a bygone era of opulence, of lavish interiors realized in fine plasterwork, entire rooms painted al fresco and barrel vaults coffered with sumptuous ornamentation in bas relief.

Pompeiian Thermae

The Romans produced not only great artists and architects but formidable engineers. A treasure remains to us in the exhaustive architectural treatise, De Architectura, by 1^st century BC Roman military engineer Marcus Polio Vitruvius. In this work known commonly known as the Ten Books on Architecture, Vitruvius dedicates three chapters of Book II to the selection of sand, lime and pozzolans for stucco and concrete works. He further devotes the majority of Book VII to proper lime stucco preparation, application and fresco work.

The greatest civilization of the ancient world coincided with the greatest understanding and development of plaster. The Romans expanded upon a significant discovery made by the Greeks: the additions of pozzolans to lime would create a plaster that sets in water. Concrete was born, architectural engineering was ascendant and the Romans would go on to construct roads, aqueducts and ports that endure to this day. Roman engineering prowess and the discovery of concrete culminated in their unparalleled architectural achievement, the Pantheon. Having an interior diameter of 142 feet at its base the Pantheon remains the largest unreinforced concrete dome ever constructed.

The Pantheon, Rome

Vitruvius treatise began to achieve widespread publication in the early 15^th century. By the late 15^th century there is written and archaeological evidence of Vitruvius’ hydraulic stucco recipes being utilized in Venice and Murano, 300 years before the advent of modern cement. Later we will explore how his writings together with archeological discoveries at the Domus Aurea would inspire creative geniuses such as Da Vinci, Michelangelo and Rafael to attain to dizzying heights of artistic expression in buon fresco and the modeling of stucco during the Italian Renaissance.

Contributed by Patrick Webb

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

In our previous post we familiarized ourselves with the concept of varietals and how they exist in wine and plaster. For wine we learned that each variety of grape possesses unique characteristics and that a few of these grapes varieties actually produce a good wine without blending, known as a varietal.

Varietals are important; however, for the French there is one contributing factor in making a truly great wine or plaster that is absolutely fundamental. That essential component is the one we have little to no control of. It is summed up in a small yet tricky to pronounce word called terroir (ter-whah).

This blog post is the second of a five part series on French traditions of wine and plaster making framed in a very wine oriented vocabulary:

• · Varietals
• · Terroir
• · Viticulture
• · Viniculture
• · Pairing

Terroir in Wine

Terroir comprises all the geologic, atmospheric and climactic conditions found within a wine-making region that give grapes the foundation they need to develop the characteristics we enjoy in our favorite wines. Just like it sounds, terroir is an extensive topic. For our glimpse into this world; however, the following overview addresses three key aspects of terroir: temperature, moisture and soil composition.

All of the world’s major wine growing regions are situated between 30˚ and 50˚ latitude in both the northern and southern hemispheres meaning that cool to moderate temperatures are optimal for wine grape growing. In cooler climates with less sun exposure (think Washington State or Germany) ripe grapes retain enough “greenness” to produce wonderfully crisp, herbaceous wines like sauvignon blanc which pairs nicely with a green salad topped with goat cheese, green beans and basil pesto. In warmer climates (California and Bordeaux) grapes remain on the vine longer sunning themselves and developing more color, sugar and complexity in the process. The resulting big, bold, fruit is why cabernet sauvignon is known as King Cab.

California and Bordeaux are world-class wine producing regions with oceans bordering both regions providing a moderate and stable climate with minimal risk of damaging frosts. Rainfall in both regions averages a healthy 29 to 34 inches annually. In general, when grapes receive less than optimal rainfall, the vines will produce fewer grapes, though often of superior flavor. In contrast, if heavy downpours occur, particularly close to the harvest time, the grapes absorb too much water, which dilutes the flavors and produces low quality wine. So balance in moisture be it rain, fog or dew is crucial to superior grape production. However, while moisture is important for the vineyard, of equal importance is the vineyard’s drainage system. This leads to our third topic of terroir: soil composition.

As a rule the best wines come from grapes that have suffered a bit; where nutrients are available, but the vine must work for them. According to The World Atlas of Wine writers Hugh Johnson and Jancis Robinson state that best soil (for vineyards) is not particularly fertile, it drains quickly thus forcing the roots downward in search of a water supply. Vineyards in the Medoc region of Bordeaux produces some of the most notable wines because beneath the gravelly topsoils are alternating layers of hard compacted sand and clay. These quickly draining surfaces force the roots to dive deeper until they reach a moist layer of sand and clay near the water table. When nutrients are too easily accessible, vines become complacent and results are one dimensional grapes with underdeveloped structure and complexity.

Terroir in Plaster

For plaster, terroir means geology. It is what nature has provided us. You can’t make something from nothing and you can’t produce a great plaster if the geology is poor. Let’s again take a closer look at the terroir of two of the minerals used to make the plaster blend Terre de Séléné: lime and gypsum.

Lime typically is derived from limestone. Limestone is sedimentary rock formed from the skeletal remains of marine creatures that accumulated on the sea floor millions of years in the past. With time and pressure these skeletons are pressed together in beds of stone.

Some limestone contains contaminants of clay or other materials that affect its chemical properties. When these "hydraulic limes" are baked they will readily react and harden when mixed with water. However, many limestone deposits found in both France and the United States are relatively pure with little contamination from clay or other materials. This type of pure limestone produces a lime that blends well with other plasters. It is the very terroir needed for the lime in Terre de Séléné.

I mentioned in the previous post that gypsum and limestone are geologically related. While limestone was forming on ancient sea beds another phenomenon was occurring in salt marsh lagoons along the shore. Through repeated cycles of seawater infiltration and evaporation gypsum, salts and other compounds precipitated and formed large masses.

Many of these masses have been preserved relatively unchanged, covered by layers of clays that protected them from erosion. In these one can find gypsum rock with many of the original impurities that give the gypsum very interesting properties often useful for construction. In many instances though the original gypsum, being more soluble in water than other precipitates, would be carried off with underground water to recrystallize in successively purer forms in subsequent locations. Many distinct forms of gypsum with diverse crystalline, chemical structures and levels of purity formed. There are gypsum crystals found in underground caves in Mexico for instance that measure over 30 feet long and weigh several tons each, the largest crystals in the world! 

Grapes, gypsum and limestone were here a long time before we arrived on the scene. Terroir is the result of millions of years of geology and current climate conditions we study and benefit from but can’t imagine to control. That being said good wines and beautiful plasters don’t make themselves. Next blog we’ll consider the human touch, Viticulture.

This article was coauthored by Angela and Patrick Webb