Glossary

Abrasive / Sand Paper Paper sheets are covered with miniscule natural or artificial crystal fragments that depending on their size give the sheet a grade of roughness. The higher the number, the finer the grade resulting in a better finish. The number can go as high as 1800/2000. It is used to smooth or clean surfaces.
Acid The word “acid” comes from the Latin acidus meaning “sour,” but in chemistry the term acid has a more specific meaning. There are some common ways to define an acid:

  • Arrhenius: According to this definition developed by the Swedish chemist Svante Arrhenius, an acid is a substance that increases the concentration of hydrogen ions (H+), which are carried as hydronium ions (H3O+) when dissolved in water, while bases are substances that increase the concentration of hydroxide ions (OH-). This definition limits acids and bases to substances that can dissolve in water.
  • Brønsted-Lowry: According to this definition, an acid is a proton (hydrogen) donor and a base is a proton acceptor. The acid is said to be dissociated after the proton is donated. This definition includes water-insoluble substances that would not apply to the Arrhenius definition.

Acidity is measured by pH (potential for hydrogen) which is the concentration of hydrogen ions when the acid is dissolved in a solution.

(Source: Wikipedia)

Acrylic Resin Acrylic resin is transparent and colorless with a consistency like molasses. With a base of ethyl acrylate, methyl methacrylate, ethyl methacrylate are use as binders in wall paint and plasters and to make varnishes.
Affresco The technique used to apply waterborne pigments on fresh, damp plaster.
Aggregate Granular stone material (sand, gravel, crushed stone) used as the binder in plaster and concrete. It is used to reduce shrinkage in lime and cement mixtures.
Alkaline In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Alkalis are best known for being bases that dissolve in water.  The adjective alkaline is commonly used in English as a synonym for base, especially for soluble bases, though this is nontechnical.The terms “base” and “alkali” are often used interchangeably, particularly outside of a scientific context, but they do not have the same meaning. While all alkaline solutions are basic, not all bases are alkaline.

(Source: Wikipedia)

Base In chemistry, a base is most commonly thought of as an aqueous substance that can accept protons. A base can be (commonly) thought of as any chemical compound that, when dissolved in water, gives a solution with a pH higher than 7.0, meaning a molarity of less than 10^-7 of H+ ions. (technically H3O+)Bases can be thought of as the chemical opposite of acids. A reaction between an acid and base is called neutralization. Bases and acids are seen as opposites because the effect of an acid is to increase the hydronium ion (H3O+) concentration in water, whereas bases reduce this concentration.

(Source Wikipedia)

Bees’ Wax Bees’ wax is a tallow-like substance that honeybees secrete when they build their honeycomb. It’s available in a pure white form, or a natural yellow-brown color, and is used as a base for a variety of furniture and floor polishes. In the past, it was used in a variety of ways: as a binder in encaustic paint (heated beeswax to which colored pigments are added), in pastels and in the finishing process; as a component in paint, normally blended with resin; as a way to soften a paint’s translucence; and to increase water repellent properties. In the past, bees’ wax emulsified with lime presumably constituted ‘punic’ wax used in encaustic.See: Wax, Cera Punica and Encaustic.
Calce The Italian word for lime. Ca(OH)2 (Mineral name: Portlandite).
Calcestruzzo The Italian word for concrete.
Calcium Carbonate This organic salt, CaCO3 is the main component of the rock used to make lime. It is widely used for the preparation of plasters such as Marmorino.
Carbonatization This is the physical-chemical process where water is released from plaster during the hardening and drying process. It allows for the reaction between spent lime (Ca(OH)2) and carbon dioxide (CO2) reforming into lime carbonate (CaCO3).
Carboxymethyl-cellulose In restoration, this is used as a thickener, emulsifier, detergent and stabilizer.
Carnauba This is very thick wax, coming from the Brazilian palm (Copenicia cerifera). It is added to waxes and polishes to make them more consistent. See: Wax.
Carrara Carrara is a town in the province of Massa-Carrara (Tuscany, Italy), famous for its valued white marble.
Casein It is a white, tasteless, odorless protein precipitated from milk by rennin, that is, from milk curds. In alkaline solution, it is used as an adhesive. It is used as a binder in paint or in plaster preparation.
Cement In the most general sense of the word, cement is a binder, a substance which sets and hardens independently, and can bind other materials together. The word “cement” traces to the Romans, who used the term “opus caementicium” to describe masonry which resembled concrete and was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick additives which were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum, cimentum, cäment and cement. Cements used in construction are characterized as hydraulic or non-hydraulic.The most important use of cement is the production of mortar and concrete – the bonding of natural or artificial aggregates to form a strong building material which is durable in the face of normal environmental effects.

Cement should not be confused with concrete as the term cement explicitly refers to the dry powder substance. Upon the addition of water and/or additives the cement mixture is referred to as concrete, especially if aggregates have been added.

(Source: Wikipedia)

Cera The Italian word for wax.
Cera Punica This is virgin bees’ wax boiled repeatedly in seawater. To make the wax soluble, niter and sodium carbonate, in addition to other components including soda and potassium are added. This paste, soluble in water, is used in the encaustic technique.See Bees’ Wax and Encaustic.
Clay Produced from the decomposition of rock, and composed primarily of aluminum silicate hydroxide, lime carbonate and silicate. It is porous, very crumbly and malleable. It can be shaped by external pressure and when it dries it, keeps its form. It becomes very hard when baked at high temperatures. There are a variety of types which depends on the percentage of aluminum silicate, iron oxide, carbonate and quartz molecules. Sometimes it is used as an additive to change certain characteristics such as baking time, hardness, refraction and porosity. When clay dries, it shrinks in volume (10%) and it loses hygroscopic water (between the molecules) which is responsible for its plasticity. A similar shrinkage occurs during baking.
Cocciopesto This is an Italian word. Coccio means earthenware and pesto means crushed.In the past, they used to crush bricks and broken roof tiles to get a sand to mix with lime to make plaster.

In Venice, it was very common to apply a layer of “Cocciopesto Plaster” directly on the bricks before applying normal lime-based plaster. It helped to protect the finish of the wall against the damp of seawater.

The addition of terracotta to slaked lime makes the slaked lime hydraulic, that is, it can harden even in the presence of water. The antique Romans were the first to discover it and used it widely.

Concrete Concrete is a construction material composed of cement (commonly Portland cement) , aggregate (generally a coarse aggregate such as gravel, limestone, or granite, plus a fine aggregate such as sand) and water.The word concrete comes from the Latin word “concretus”, which means “hardened” or “hard”.
Cotto This is the Italian word used for bricks and other materials made of terracotta.
Dry Wall A board made of several plies of fiberboard, paper, or felt bonded to a hardened gypsum plaster core, is used as a divider and for covering internal walls.
Dye A water or oil soluble substance which gives color to other materials.
Encaustic This is an ancient technique which also goes by the term “hot wax painting”. The artist heats beeswax to the liquid stage; then mixes in pigmentation. The resulting medium is applied to a surface and reworked once it has dried. The word comes from the Greek meaning ‘engrave with fire’ which describes this painting technique which uses hot wax as a binder for pigments.
Epoxy Resin This compound came into use in 1949. It is composed of an epoxide resin, therefore its name) and a polyamine hardener which, when mixed together, harden at room temperature releasing heat (for this reason these resins are called thermal hardeners). Yellowing occurs when exposed to sunlight.
FRP – Fully Refined Paraffin Mineral Wax with an oil content of less than 0.5%
Fresco See “Affresco”.
Gesso di Bologna (Plaster Gipsum of Bologna) CaSO44 +2 H2O, calcium sulfate hydroxide. It is found in its natural state as a mineral and is used in the preparation of plasters. It is the main component in Spatolato Veneziano.It is also known as white plaster of Meudon, plaster of Spain and plaster of Vilt. It is a calcium carbonate that comes from sea shell deposits. It is the stable form of chalk. It can be mixed with any binder without changing its characteristics.
Glitter Small mineral, metallic or plastic particles similar to fish scales that reflect light or sparkle.
Glue – Natural Natural Glue: Glue is a substance used for joining materials.Before 1930 all the glues were of natural origin: animal glue is obtained by boiling bones and hides (For example, “Lapin” glue comes from rabbit hides).

One of the strongest natural glues is Casein which is obtained from milk.

Another type of glue is derived from fish.

These glues were often used when finishing walls: in the preparation of paints and plasters such as Spatolato Veneziano. Even today, they are used in restorations.

Vegetable glues, which are very weak, were derived by boiling flours and starches in water and adding garlic juice.

Grassello The Italian word for slaked lime. There is also a modern wall finish called grassello made of a material which is predominantly slaked lime.
Gypsum Gypsum is one of the more common minerals in sedimentary environments. It is a major rock forming mineral that produces massive beds, usually from precipitation out of highly saline waters. Since it forms easily from saline water, gypsum can have many inclusions of other minerals and even trapped bubbles of air and water.Gypsum has several variety names that are widely used in the mineral trade.

  • “Selenite” is the colorless and transparent variety that shows a pearl like luster and has been described as having a moon like glow. The word selenite comes from the Greek for Moon and means moon rock.
  • Another variety is a compact fibrous aggregate called “satin spar”. This variety has a very satin like look that gives a play of light up and down the fibrous crystals.
  • A fine grained massive material is called “alabaster” and is an ornamental stone used in fine carvings for centuries, even eons.

Crystals of gypsum can be extremely colorless and transparent, making a strong contrast to the most common usage in drywall. The crystals can also be quite large. Gypsum is a natural insulator, feeling warm to the touch when compared to a more ordinary rock or quartz crystal. Sheets of clear crystals can be easily peeled from a a larger specimen.

Gypsum crystals can be extremely large – among the largest on the entire planet.

  • Color is usually white, colorless or gray, but can also be shades of red, brown and yellow.
  • Luster is vitreous to pearly especially on cleavage surfaces.
  • Transparency crystals are transparent to translucent.
  • Crystal System is monoclinic; 2/m
  • Crystal Habits include the tabular, bladed or blocky crystals with a slanted parallelogram outline. The pinacoid faces dominate with jutting prism faces on the edges of the tabular crystals. Long thin crystals show bends and some specimens bend into spirals called “Ram’s Horn Selenite” Two types of twinning are common and one produces a “spear head twin” or “swallowtail twin” while the other type produces a “fishtail twin”. Also massive, crusty, granular, earthy and fibrous.
  • Cleavage is good in one direction and distinct in two others..
  • Fracture is uneven but rarely seen.
  • Hardness is 2 and can be scratched by a fingernail.
  • Specific Gravity is approximately 2.3+ (light)
  • Streak is white.
  • Associated Minerals are halite, calcite, sulfur, pyrite, borax and many others.
  • Other Characteristics: thin crystals are flexible but not elastic, meaning they can be bent but will not bend back on their own. Also some samples are fluorescent. Gypsum has a very low thermal conductivity (hence it’s use in drywall as an insulating filler). A crystal of Gypsum will feel noticeably warmer than a like crystal of quartz.
  • Notable occurrences include Naica, Mexico; Sicily; Utah and Colorado, USA; and many other localities throughout the world.
  • Best Field Indicators are crystal habit, flexible crystals, cleavage and hardness.

(Source: Article by Amethyst Galleries, Inc.)

Hydraulic Lime Hydraulic lime is a variety of slaked lime used to make lime mortar. ‘Hydraulicity’ is the ability of lime to set under water. Hydraulic lime is produced by heating calcining limestone that contains clay and other impurities. Calcium reacts in the kiln with the clay minerals to produce silicates that enable the lime to set without exposure to air. Any unreacted calcium is slaked to calcium hydroxide. Hydraulic lime is used for providing a faster initial set than ordinary lime in more extreme conditions (including under water).

(Source: Wikipedia)

Intonachino A traditional Italian plaster usually made of lime and marble grains. It is colored by the addition of pigments, but can also be obtained by adding colored marble grains.
Lime Calcium oxide is also known as burnt lime, quicklime or unslaked lime; Calcium hydroxide is also known as slaked lime, slack lime or pickling lime; Hydraulic lime.Lime, which is a solid white substance, is produced by baking calcareous rock. When treated with water, the lime swells, heats up and becomes calcium hydroxide or spent lime. Wetting it with a quantity of water which is two and a half times its weight, you obtain slaked lime or lime putty, which is the binder for mortar. By mixing the spent lime together with excess water you get a white liquid called lime milk, which is used as a base for various methods of dry painting. Lime can be either rich or poor. Rich or fat lime is derived from pure, or very nearly pure, limestone whereas poor lime comes from magnesium or argyllic (clay) limestone which is less pure. The rich limes are more suitable for painting. They become spent faster, give a high quality shine and set well.
Lime Paint See Whitewash.
Lime Putty See Lime.
Lime Water The common name for saturated calcium hydroxide solution.
Magnesium Magnesium in its form, MgCO3 is part of the rock from which lime is extracted and can make up 20% of it.
Marble Marble is a metamorphic rock composed primarily of calcium carbonate (CaCO3). Used since antiquity for sculpting statues, it has always been used in the building trade for the construction of decorative and load bearing elements.
Marmorino A finishing plaster with a base of spent lime and powdered rock. It is called Marmorino because it is the most natural imitation of marble in terms of both composition and its final appearance.
Marsiglia Soap / (Marseille Soap) It is unrefined soap and therefore contains more alkaline than regular soap.
Mica The word mica comes from micare, the Latin word for shine. The term mica stands for a group of phyllosilicates. These minerals tend to form pseudo-hexagonal crystals. The characteristic exfoliating of mica is due to the laminating disposition of these sheets of juxtaposed crystals. The main producers of mica are China, The United States, South Korea and Canada.
Micro-crystalline Wax This wax, obtained from a mixture of heavy lubricating oil distillates, has an ill-defined crystalline structure and a dark color. It generally has a higher melting point and viscosity than paraffin. Depending on its elemental composition, it can range from soft and sticky to hard and brittle.
Mother of Pearl This is an organic-inorganic composite material which some mollusks produce as an inner shell layer. It is very strong, resilient, and iridescent.
Nacre Synonymous with Mother of Pearl.
Paraffin Obtained from petroleum distillates, it is composed of about 90% short chains of hydrocarbons (from 20 to 30 carbon atoms). Some of its properties are:

  • Waterproof
  • Nontoxic
  • Non-reactive to other components
  • Burns with a clean flame
  • Transparent
pH pH is a measure of the acidity or alkalinity of a solution. It means “potential for Hydrogen ion concentration.” pH can be measured if an electrode is calibrated with solution of known hydrogen ion concentration.  pH is the negative logarithm of the molarity of hydrogen ions in a given solution. Pure water is said to be neutral. The pH for pure water is close to 7. Solutions with a pH less than 7 (more hydrogen ions) are said to be acidic and solutions with a pH greater than 7 (less hydrogen ions) are said to be basic.
Pigment A powdered substance, either natural or artificial, which colors another material. It is not soluble in water. Substances which are soluble in water are dyes and colorants.
Pittura a Calce The Italian word for lime wash.
Plaster of Paris Plaster of Paris is made by heating gypsum to about 300 degrees Fahrenheit, which drives 75% of the water out of the mineral. This reaction absorbs energy, enabling a sheet of drywall containing it to be fire resistant. Heating further to about 350° F drives out the remaining water and results in conversion to the mineral, anhydrite.
Portlandite The mineral name of Lime.
Pozzolana This sandy, volcanic ash is a siliceous material which reacts with calcium hydroxide in the presence of water to form hydraulic cement. It was often used in Ancient Rome to produce plasters. In Venice, terracotta was substituted for it.
Primer This liquid product is applied by brush or roller on surfaces to be painted. This insure good paint or plaster adhesion. Another reason to use primer is to join two substances which are normally difficult to bind together, like plaster and mortar (because of their opposing pHs).
Punica Wax See: Cera Punica.
Puntinato The Italian word for some wall finishes which show speckling caused by the presence of black quartz sand.
Quartz Silicon dioxide, SiO2, from the German, quarz is a mineral which is found mainly in the Earth’s crust (making up about 12% of its volume).
Rasato di Calce A traditional interior finish used in Venetian construction consisting of liquid lime. It is applied with a brush on lime plaster and sand, and smoothed with a metal trowel. Originally it was applied in up to six or seven layers.
Resina A class of polymer substances used as a principle component in paints.
Restoration Conservation of a work of art, returning it nearest to its original condition when there has been deterioration.
Sand Granular material composed of the detritus which results from the pulverization of rock which is carried to streams, rivers or seas or lies in caves. It is used in mixtures as an aggregate.
Scagliola A decorative technique used on walls or floors. In Italy it is also called meschia, marble paste or artificial marble. In Germany it is called Stuckmarmor. And in England it is known as Bossi work (from the Italian craftsman who worked in Dublin in the 1700’s). There was a gradual diffusion of this technique throughout Europe between the 17th and 19th centuries. The word Scagliola come from the kind of plaster used which comes from mixing glue made of bones and colored pigments. See: Scagliola Gypsum.
Scagliola Gypsum A finely powdered plaster which when mixed with water solidifies to a hard porous mass. It solidifies in 15-20 minutes and is useful for making molds or forms, but it is not strong enough to be used as wall plaster. When borax is added to the water during the mixing process, the plaster becomes more resistant.
Semi-refined Paraffin Wax Wax with an oil content of 1 to 3%
Slack Wax Mineral wax (it can be paraffin or micro-crystalline) with a high content of oil.
Slaked Lime A thixotropic material composed of calcium hydroxide Ca(OH)2 and water. This process involves slaking baked calcium hydroxide, with an ample amount of water and aging it in a pit for a minimum of 3–4 months until it becomes fully hydrated.
Spatola A small trapezoidal-shaped tool with a flat blade, made of wood or metal used by masons, plasterers, and painters for missing or spreading mortar, plaster, or paint.
Spatolato Veneziano This is a traditional, polished Venetian plaster. It is composed of plaster of Bologna, natural Lapin glue, linseed oil and colored pigments.
Sponge Float A trowel with a small palette covered with a layer of sponge which is attached to a handle. It is used for smoothing out plasters.
Stucco The Italian word for finishing plaster made of lime and powdered marbled or a base of plaster. The word stucco can also mean wall decoration in relief.
Stucco Lustro / Stucco Lucido Polished Stucco is a plaster made of 1 part plaster, 5 parts grassello, 5 parts of fine marble powder, and glue. It is often confused with Marmorino because they are both shiny.
Stucco Mantovano A traditional finishing plaster coming from the city of Mantua. It is made of lime putty colored with pigments and applied in several layers with a trowel.
Stucco Romano The Roman plaster, similar to today’s Marmorino, was composed of up to seven layers of plaster made of lime putty and rock powder with a final smoothing which gave it a slight sheen.
Tadelakt Tadelakt is a shiny, lime wall coating which is water resistant. It can be used for both interiors and exteriors. It is the traditional coatings of the palaces, hammams and baths of the riads in Morocco. This finish is polished with river stones and treated with a soft, black soap to acquire its water resistance. Tadelakt has soft look with undulations caused by being worked with the river stones. This gives it great decorative capacities.
Terracotta This is produced by baking clay at temperatures of about 950°C. Its color varies from light yellow to deep red. Dishes, vases, pots, bricks and tiles are made of terracotta.
Thixotropy The property of a material which is a gel when in repose and which liquefies when it is agitated.
Travertine This is a calcareous, sedimentary rock which was often used for building, particularly in Rome, until the first millennium BC.
Trowel A special kind of spatula which has a rectangular shape and a handle. It is used to apply mortars and plasters. It can be made of a variety of materials, but is usually metallic.
Venetian Plaster Stucco Veneziano.
Wax The term wax indicates an organic substance, natural or synthetic, such as plastic, which is solid at room temperature and becomes liquid when melted. The common characteristics of waxes are:

  • A solid state at 20° C (68° F)
  • A liquid state above 40° C (104° F)
  • A relatively low viscosity, just above the point of fusion
  • A combustion capacity (during which it produces a yellow flame)
  • Impermeable and insoluble in water
  • The capacity to form creamy or gelatinous substances by being dispersed in solvents or waterproofing emulsions.

A catalog of existing waxes:

With the technological evolution, the products on the market termed wax have multiplied, and have a variety of chemical compositions and characteristics.

The cataloging is done in general terms according to their origins:

Natural waxes:

  • Animal (bees’ wax, lanolin, tallow)
  • Vegetable (carnauba, candelilla)
  • Fossil or Mineral (ceresine, montan, ozocherite)
  • Petroleum (paraffin, microcrystalline, petrolatum)*

Synthetic waxes:

  • Ethylene polymers (polyethylene and polyol ethers-esters)
  • Naphthalene chlorates
  • Fischer-Tropsch waxes

*Waxes derived from petroleum:

Unrefined petroleum extracted from underground is a mix of various hydrocarbons and results from the decomposition of small aquatic plants and animals that lived in the oceans millions of years ago.

After the raw material is taken to the refinery, it is undergoes a series of complex processes to obtain a variety of finished products. One of these derivatives is lubricating oil from which we get wax.

Wax Paint See Encaustic.
White Wash A type of paint made from slaked lime. Chalk (whiting) can be added along with various other additives.