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Historical Notes On The Origins Of Paints And Italian Plasters

Paints: Distempers - Lime Based Paints

Distempers

Distempers are those paints obtained by mixing water and glue. More in general they are those paints in which charges and pigments are kept together by a glue or a binder so to create a homogeneous amaigame.

The name "distemper" comes from "stemperare", ie: make a paste from a powder by blending with a liquid. In the ancient times distemper was used also in reference to blends with paints and oils. Afterwards, it has been referred only to identifying pigments kept together by animal glues, vegetable glues, egg, milk and so on. In the years distempers composition evolved and changed so much to be sometimes confused, in its results, with frescoes or oil paints.

From the explanation above, it is possible to summarize that distemper can be defined as a kind of paint containing pigments, bound by different gluing substances, to be applied pigmented on a dry base.

Distemper is an evolution:
Pigments and Fillers
Binders
Ground marble dust (calcium carbonate)
Earth Pigments
Egg yold, egg white, bones glue, rabbit glue, fish glue, milk, milk coagulates, (casein). Four glue, rice glue,
Ground marble dust (calcium carbonate)
Earth Pigments
Casein blended in lime-milk, cooked and raw linen-seed oil.

Meudon white,
Earth pigments, iron oxides

Cellulose ethers
Meudon white, calcium carbonate
iron oxides, organic colorants
titanium dioxide
Cellulose ethers
Polyvinylic resins
Calcium Carbonate
iron oxides, organic colorants
titanium dioxide

Cellulose ethers
Acrylic resings, Ethylene resins, Vynilversathate resins, styrol-acrylic resings

In a nutshell, distemper is the mother of today's synthetic latexes, which range from present distempers to "breathable" latexes, from water-repellents to washable paints, from quarts-based paints to syloxanics.

Lime-Based Paints

Whereas distempers in ancient times were used mainly to obtain decorations, lime-based paints were used most-of-all to paint big surfaces and facades.

After having known centures of heavy-use, in the second half of the 19th century, lime-based paints lost popularity. Only in the last 10 years lime-based paints became popular again, most of the time somewhat modified to make it more suitable to present times.

Raw materials suitable to lime-based paints are lime-grasselio and "fiore" hydrated lime. Both are aerial limes (ie: they harden slowly once in contact with air). Both are derived from the same material (cooked lime stones) whether dry-ground or made wet and left to dry.

Pigments, fillers, mineral binders
Organic binders
Lime grassello or hydrated lime
Meudon white
Earth Pigments
Bones glue, fish glue, leather glue, flour glue, rice glue, potato flour glue, milk casein, egg yolk, egg white, ficus milk, nut oil, olive oil, raw and cooked linen oil.
Lime grassello or hydrated Lime
Calcium carbonate
Earth Pigments
Iron Oxides
Titanium Oxide

Methyl cellulose
Acrylic resings
Linen oil
Pine oil

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Stuccos: Lime-Based - Gypsum Based

Lime-Based Stuccos

In general, lime-based stuccos are meant those finishing plasters composed mainly of lime grassello or hydrated lime, blended with marble powder (calcium carbonates) and organic substances.

According to the grain size of the filler (marble powder) they would accomplish different effects:

grassello lime-plaster shiny finish
marmorino lime-plaster satinated finish
travertine lime-plaster matt with scars of variable depth

Lime-based plasters and their evolution:

Pigments, fillers, mineral binders
Organic binders
Lime grassello or hydrated lime
Meudon white
Earth Pigments
Lime grassello or hydrated lime
Inorganic pigments, earth pigments

Fish glue, rabbit glue, casein, virgin wax,
soap, egg, olive oil, linen oil

Oil
Methyl cellulose, acrylic resin

Gypsum-Based Stuccos/Putties

Gypsum-based putties (or synthetics) were made of water, gypsum and a solution of glues. They were used for interiors only for decorative levellings or base-reliefs. They had the same durability and consistency of lime-based stuccos with a fast hardening process and no causticity at all. On the other hand, they had a very small workability time-frame, being gypsum a hydraulic material, it would harden in just a few tens of minutes. In time, with the development of polyvinylic resings, gypsum for decorative decorations was substituted by calcium carbonate, which allows a workability similar to lime.

Gypsum-based stuccos and their evolution:

Fillers and pigments
Binders
Gypsum
Earth Pigments
Fish glue, rabbit glue, flour glue
Gypsum, hydrated lime
Earth pigments
Fish glue, rabbit glue, casein
Gypsum, calcium carbonate
Inorganic and organic pigments
Methyl cellulose
Calcium carbonate
Inorganic and organic pigments
Methyl cellulose
acrylic resin

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Plasters

Lime-Based Plasters

Since forever, plasters conjugated their aesthetic function with the protection of the building.

The first examples of plasters can be identified with blends of mud and clay, frequently modified with vegetale materials like leaves, straw or animal dung.

By the times of the Greeks and the Romans, plaster was composed of a number between 4 and 7 different layers. Today the usual habit is 3 layers, on top of which decoration is created.

The first layer starting from the bricks is composed of a blend of cement, hydraulic lime and coarse sand (approximately 2 to 8mm).

The second layer is composed of middle-size sand (0.6 to 2mm) blended with hydraulic lime and hydrated lime.

Plasters and their evolution:

The composition of plasters remained practically unchanged from the Greeks. The only variations have taken place in the number of coats and in the finishing of the plaster. A plaster application at the Romans' time for a patrician house was composed of 7 layers:

Rinzaffo Pozzolana, lime and coarse sand
Arriccio Possolana, lime and mid-size sand
Velo Lime and fine sand
Velo Lime and fine sand
Stucco Lime and marble dust
Stucco Lime and marble dust
Stucco Lime and marble dust

Cement-Based Plasters

Cement-based plasters are very similar to lime-based plasters as far as granulometry is concerned. Different from lime-plasters, they do greatly reduce their permeability to water and become very hard even in the presence of high humidity.

They are most suitable for structures in direct contact with the weather where high surface durability is required.

They are absolutely unsuitable to support lime-based cycles.

Synthetic Plasters

They can have the same granulometry of the inerts, quite like the lime or cement-based ones. Nevertheless, their binder is a resin instead of a mineral. Such fact implies an overall durability higher than lime or cement-based plasters. On the other hand, such substrate prevents breathability.

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Colourants

The first colorants used in paints were earth pigments; they are available in nature and change colour according to the place they come from and the kind of sediment. The best known earth pigments, presently used in restoration jobs are the following:

Vine Black Obtained by the cooking of grapevine wood
Manganese Black Composed of Managanese dioxide
Ocres and yellow earths

Composed of clay and silica.
Famous among them:

Sienna earth - manganese dioxide with iron oxide
Burnt Umber - cooked raw umber
Kassel earth A kind of bituminous earth
Red earths Verona red, Pozzuoli red, Nuremberg red, with nuances from orange red to violet red according to the oxidation degree of the iron oxide in the mineral.
Green earths Iron hydrosilcate with magnesium salts and potassium originated by sea clay. The most appreciated one is the Brentonico green.
Blue earths With their well known weak resistance to clay alkalinity. For that reason blues in frescoes were usually made only with distempers. Giotto's skies are quite famous even today.

Earth pigments were ground and dispersed in water before use. They were left separate from the water which was changed a few times to take away as much impurities as possible. After that phase they were blended with milk and thus used in frescoes or blended with distempers or lime paints.
In ancient times bright colours were obtained from organic materials like leaves, flowers, fruit, insects, and clams.

Following this phase, oxides became most used. They had similar shades to the earth pigments but were obtained from the metals: iron oxide fo ryellow and red, chromium oxide for green, etc.

Today, together with oxides, organic colorants are widely used. They are obtained form metals (eg: green and blue from copper) or from chemical synthesis (reds, yellows) which , unlike standard oxides, result in very bright shades.

Fresco Paint

Fresco painting is a quite simple kind of painting. It must be made on lime-based plaster before the plaster dries. Normally such techniqus are used with natural pigments like earth pigments, washed and blended with milk.

The wet substrate allows for the colors to penetrate deeply and become one with the plaster.

Encausto Paint

Encausto paint, used by Egyptians, Greeks and Romans, has been formulated in many different, often contrasting, ways. Even today's analysis on different works leads to stunningly different results.

One of the few raw materials which remained common to all those formulations is the bees-wax.

Encausto comes from the ancient Greek language and means "to burn". In painting "Encausto" refers to a technique of blending pigments and wax through heat.

In a nutshell, Encausto is a wax or a distemper using wax as its main binder. It's difference with the "cold wax technique" is given by the fact that the former is obtained by applying the pigmented wax through heat, on a heated wal, after that the pigment and wax have been blended through heat. On the contrary, the "cold wax technique" wax is blended with a solvent (turpentine) and applied on a cold wall.

Today many people refer to Encausto in an inappropriate way, referring to shiny finishing plaster, both lime-based and synthetic.

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