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Vintage Plaster Traditions: Viniculture

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In our previous article, we considered "Viticulture," the cultivation of the grape while on the vine 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, the artisan must utilize his or her intelligence as well as fully engage all of their senses to further influence what nature has provided. Man as creator of the "artificial" in the literal Latin meaning of the word, that which is "made by craft."

Viniculture in Wine

As we have seen thus 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.

Grape Harvest from the Tacuinum Sanitatis

Grape Harvest from the Tacuinum Sanitatis

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.

Bacchus fresco, House of the Centenary

Bacchus fresco, House of the Centenary

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 vapor that can be attributed to its platelet structure, composed of tetrahedral sheets. This property contributes significantly to interior air quality by allowing vapor 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 design, 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, color, 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. – Contributed by Patrick & Angela Webb

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