MATERIALS

LIME

Lime, from the Latin calx, is an inorganic binding based on calcium compounds, obtained from the firing of calcareous rocks and the chemical reaction with water that gives a solid and resistant compound.   

The therm lime indicates a series of building materials, known since ancient times, that were obtained thanks to a high-temperature cooking of limestone, marble, shells or other materials containing calcium carbonate, yellowish in color.    

The Romans abd Phoenicians had already learned to use lime as a building material, mixed with sand to form a mortar. 

 Vitruvius, in his work De architectura describes its production starting from white stones (limestone), fired in ovens where they lose weight (today we know as a result of the release of carbon dioxide). The material thus obtained, quicklime, is subsequently “quenched” with was plenty of water, giving rise to “slaked lime”.   

Initially it was used in the form of “aerial lime” (which hardens only if in contact with air) it was subsequently mixed with pieces of baked clay (pottery, bricks, etc.) or pozzolana, a sand rich in silica, which alters its resistance and impermeability characteristics, and above all it allows the setting and hardening of the mortar even in environments not in contact with air (typically underwater). 
Thus were born the “hydraulic mortars”, although based on aerial lime.

POZZOLANA

Pozzolana is an effusive eruptive rock, the term is extended to volcanic powders of various kinds, capable of reacting with lime to give mortars with remarkable hydraulic properties, particularly resistant to water. 

The name pozzolana derives from Pozzuoli, Puteoli powder, exported all over the world, originally mainly from the Phlegraean Fields. 

As in the past, pozzolana is still an important element in the production of cements, in particular those made of pozzolana, having particular resistance to chemical agents and perfect for underwater use, by virtue of their resistance to the dissolving action of marine waters. 

In fact, pozzolana became so popular during the Roman Empire thanks to its hydraulic characteristics and great works were made such as: artificial basins, bridges, port piers and even domes (such as that of the Pantheon). If even today, after almost 2100 years, we can still admire these structures we only have to thank the quality of these materials and impeccable execution.

COCCIOPESTO

Cocciopesto is a building material used as a waterproof coating for both indoor and outdoor floors, but also for wall covering. 

It is composed of brick fragments (tiles or bricks) minutely crushed and fine mortar based on aerial lime. 

It is laid in several layers, characterized by different granulometries, which are beaten and wetted several times. It has been used since Roman times as a waterproofing agent (covering tanks or cisterns) or for floorings. 

Even today it finds its application with the same importance.
  
The ancient Romans called it “Opus signinum”, a Latin term deriving from the city of Segni (Signa), near Rome, where it was invented according to ancient sources. Vitruvius describes its manufacture and use.  

It is particularly suitable for the recovery and restoration of buildings in historic centers and also for new architectural solutions.

BRUSONI

Brusoni: derives from the ancient Venetian language (brusà = burnt, overcooked), a term still strongly used in Veneto, especially in Venice, where the ancient term “brusone” means brick cooked too much. These strong bricks of black or grayish color or with yellowish shades were cooked in furnaces by firewood. In nature it is extremely porous.   

These “brusoni” were used in ancient times in fine architecture for the construction of floors on wooden ceilings in villas, palaces and castles.

CALCINAROLI

The “calcinaroli phenomenon” indicates the typical chemical reaction of aerial lime, which occurs after the “extinguishing” of quicklime CaO (calcium oxide). The limestone (CaCO3) during firing dissociates according to the reaction: CaCO3 -> CaO + CO2. Calcium oxide (CaO, also called quicklime) is obtained and carbon dioxide (CO2) is released. The lime extracted from the firing kilns can be put directly on the market as lump quicklime. More often it is transformed into hydrate (slaked lime) according to the exothermic reaction: CaO + H2O -> Ca(OH)2 or, with the addition of water (H2O) to calcium oxide (CaO) a calcium dihydroxide (Ca(OH)2, also called slaked lime) is obtained.

The quicklime extinguishing phenomena can take place in two ways:

• by sprinkling: with the supply of water strictly necessary for the reaction. Atomized and pressurized water is used, favoring the formation of a powder (lime flower), sold in bags, used for mortars and lime paints.
• by immersion: with a supply of water superabundant to the reaction. It is called “in large waters” and is carried out on site in large tanks with high edges, in order to avoid accidents since the reaction is highly exothermic and the heat production determines the boiling of water. At the end of this phase, before the total evaporation of the water, the lumps are covered with a layer of sand. The slaked lime thus obtained is called “grassello” in italian, (white, dense and greasy) and cannot be used before fifteen days for masonry mortars and before three months for plaster mortars.

It can happen, however, that some lumps of quicklime end up extinguishing after use, producing swelling and material disintegration, often circular,  due to their increase in volume.

This is the phenomenon of calcinaroli and occurs when using unaged grassello or defective hydrated lime.

Once the hydrated lime has been applied, the fllowing reaction take place in the presence of the air: Ca(OH)2 + CO2 -> CaCO3 + H2O

This process is called the “setting and hardening reaction”. Slaked lime (Ca(OH)2) in contact with carbon dioxide (CO2) reforms the initial element, limestone (CaCO3) and releases water.

MARBLES

Marble is a metamorphic rock composed mainly of calcium carbonate. It has been used since ancient times as a material for sculpture and architecture. In this sense, the term is also used to indicate other “polishable” stones, whose surfaces can be made shiny through sanding. 

Marbles have multiple colors, depending on the quality and arrangement of their minerals. The presence of quartz, silicates, sulfur, metal sulphides, magnetite, fluorite, mica, chlorites and gypsum – concentrated, diffused or arranged in geodes – can gives colors ranging from white to gray-black, green, pink, red, yellow with a variety of striations, clouds and, arabesques. They are characterized by good hardness, resistance and above all excellent polishability. Their sculptability is all the more difficult the larger the size of the crystals. They are used indoors and outdoors, depending on climatic conditions, for all types of architectural and artistic applications. 

The most common Italian varieties of marble come from the Apuan-Versilia area (the most renowned area in the world for its enormous marble production capacity), then there are the Bianchi di Carrara, the Arabescati and the Statuari; other marbles are also extracted in the provinces of Bolzano (Bianco Lasa), Udine (Marmi di Timau), Novara (Crevola d’Ossola, Marmi di Valle Strona) and Siena (Giallo di Siena). From a commodity point of view, all rocks susceptible to polishing are considered marble; other metamorphic rocks such as gneiss, cipollini and serpentines are thus defined as marbles, but also many well-polishable sedimentary lithotypes such as calcareous breccias (Breccia Aurora, Breccia Pernice), calcareous alabasters and compact limestones (Botticino, Perlato Coreno, Asiago, Aurisina, Chiampo, Custonaci, Verona marbles).  

Lastly, the term marmor (pl. marmora) was adopted in Roman antiquity to describe all rocks susceptible to polishing (real marbles, limestones, alabasters, most of the breccias). 

CLASSIC MARBLES

This category is composed of a wide range of irregularly shaped and unworked natural stones such as marble, porphyry and granite available on different grain sizes. The main uses of granules are for urban furniture, Venetian flooring, decoration of public and private green areas and architectural gravel.

PEBBLES

The pebble is a stone (rock) made smooth by the action of water, especially the water that flows in rivers and streams. In construction, pebbles are used as flooring and in gardens. You can find pebbles of marble, porphyry and granite.

NATURAL PIGMENTS

Natural earths are all those mineral substances provided by nature.

These are salts, acids, sulphides, existing in different forms in the soil in more or less deep deposits. They have stratifications of various types, depending on the geological era that allowed their formation. This long geological formation attributes to the soils  peculiar coloring and resistance characteristics, that are further enhanced after the various stages of processing which, for some types, also includes calcination.

The burnt earths (earths of Siena, particularly those of Mount Amiata), the yellow earths, the green earths, next to vegetal blacks such as nero di vite and whites of horns and oyster shells or, later the binachi di San Giovanni, come out of the Middle Ages from a fresh painting to enter in the great works of the Italian Renaissance.

These masterpieces are the most evident demonstration of the immortality of these earths, and testify that the colour intensity of ochres, of the terre ombre di Cipro and the terre di Siena, are unreachable by other modern pigments, as well as the transparencies and shades. All characteristic and indispensable in artistic painting and conservative restoration.

These below are some of the natural earths used by Feltracco Fratelli:

Arancio Intenso
Blu Deep
Bruno Uso Cassel
Brown Ceram
Corinthian Purple
Limonite di Cipro
Nero Roma
Nero Vite Germania
Ocra Avana
Ocra Desert
Ocra Dunkel
Ocra Icles Limone
Ombra Bruciata
Ombra Cipro
Rosso Ercolano
Rosso Pozzuoli
Rosso Veneto
Siena Bruciata
Terra Gialla
Terra Ombra
Terra Ombra Bruciata
Terra Ombra Cipro Bruciata
Terra Ombra Cipro Naturale
Terra Ombra Naturale
Terra Ombra Naturale Verdastra
Terra Ombra Bruciata
Terra Rossa
Terra Siena Bruciata
Terra Siena Naturale
Terra Verde Antica
Terra Verde Brentonico
Terra Verde Nicosia
Verde Acqua

Chemical composition: Mineral oxides of natural origin (coeladonites-hematites-limonites-manganesites) in variable combinations depending on the various types (on average 20-40%).

SEMIPRECIOUS STONES

Gems are minerals that differ in rarity, transparency, color and brilliance. They are used for the production of luxury furniture, high quality finishes and amazing manufactures, their uniqueness is linked to aesthetic appearance and optical properties.

AGATE

The name Agate derives from the river Achates in Sicily, today called Dirillo. 

Agates are formed in the cavities of volcanic rocks in the form of round-shaped or almond-shaped deposits. The typical striations of Agate are due to the oxidation of manganese, iron and other minerals. 

Agate is a striped Chalcedony with concentric bands, which can be of different colors or of a single color. Agate belongs to the group of microcrystalline quartzes. 

Agate is a much desired gem since ancient times, both for its beauty and for its hardness: in 3000 BC it was already used in the East for decorative and practical purposes, such as for the production of vases. In the world of gems has found its use as a precious stone and seal. In Ancient Rome, carved Agates were particularly popular, gems worked with a particular cutting technique according to a specific drawing. 

In the Bible, Agatha is mentioned in the second book of Moses as one of the gems of Aaron’s breastplate. Sardonyx, a variety of Agatha, belongs to the twelve stones that made up the foundations of the wall of Jerusalem. 

Even in the Middle Ages the Agate was a particularly loved gem. It was customary, for example, to tie an Agate to the horns of oxen as a positive influence on the future harvest. 

Agates show colored streaks on their surface; The individual layers of these wonderful colored bands can be transparent or even opaque with a strong fluorescence in yellow, white or brown shades. 

The different colors are caused by the presence of iron and manganese. The layers of the Agate can show different intensities of colors, but inside the geode they are almost identical.

OBSIDIAN

Obsidian is an effusive rock, mainly or completely glassy rock, and therefore also indicated as volcanic glass, which is formed by rapid cooling of lava of variable composition.   

Due to the lack of recognizable minerals, only the chemical analysis or the refractive index measurement can allow the petrographic classification of obsidians that is constituted by: liparitic, trachytic, dacitic, andesitic and basaltic.   

The most common have an acid composition, similar to that of quartz porphyries. Obsidians, mostly blackish in color, show conchoid fracture and sharp edges. The oldest obsidians, following a slow process of recrystallization, have a cryptocrystalline or even microcrystalline structure.    

Since the ancient Neolithic, obsidian has been used, throughout the Mediterranean basin, for the manufacture of particularly beautiful and sharp tools that were exchanged even at long distances. the physico-chemical analyses demonstrated that the most important raw material sources in this area were, the Lipari islands, Monte Arci in Sardinia, and the Greek island of Melos.    

In later times, obsidian is used for the manufacture of elaborate ornaments and ritual use, typical of state civilizations such as Egypt or, in the New World, the Aztec empire.

TRANSPARENT GLASS AND GLASS PASTE

Glass is a solid, amorphous, rigid and transparent artificial material that is obtained from the slow cooling of a viscous liquid obtained, in turn, from the fusion of silica sand and other components.   

Silica sand is a sand that contains very fine quartz crystals (a mineral of silica). When this sand is heated to high temperatures it does not pass into a liquid state but has the typical consistency of hot honey; This state is defined as viscous because it is characterized by viscosity, that is, the difficulty of the particles that form the material to flow with respect to each other as it happens in liquids.

When this viscous liquid cools and passes into the solid state, the particles that form it do not have time to arrange themselves in an orderly manner (to crystallize) and its internal structure therefore remains disordered. For this reason the solid obtained is defined as amorphous which means “without a form” and this condition determine many of its properties. 

In chemistry, glass is defined as a liquid with high viscosity; a liquid that is not completely crystallized, but it appears solid due to its high viscosity.

The only glass of natural origin is obsidian, a rock that is obtained by vitrification of magma (formed of silicates: minerals containing silica) which, escaping from the volcano, cools rapidly on contact with the outside air and does not have enough time to create crystalline structures. 

Glass is one of the oldest known materials and is closely linked to the history and cultivation techniques of different civilizations. 

Glass is widely used in craftsmanship and architecture.