Earthen plaster - AbsoluteAstronomy.com

Earthen plaster is a blend of clay, fine aggregate, and fiber. Other common additives include pigments, lime

Lime (mineral)

Lime is a general term for calcium-containing inorganic materials, in which carbonates, oxides and hydroxides predominate. Strictly speaking, lime is calcium oxide or calcium hydroxide. It is also the name for a single mineral of the CaO composition, occurring very rarely...

, casein

Casein

Casein is the name for a family of related phosphoprotein proteins . These proteins are commonly found in mammalian milk, making up 80% of the proteins in cow milk and between 60% and 65% of the proteins in human milk....

, prickly pear cactus juice (Opuntia

Opuntia

Opuntia, also known as nopales or paddle cactus , is a genus in the cactus family, Cactaceae.Currently, only prickly pears are included in this genus of about 200 species distributed throughout most of the Americas. Chollas are now separated into the genus Cylindropuntia, which some still consider...

), manure

Manure

Manure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil...

, and linseed oil

Linseed oil

Linseed oil, also known as flaxseed oil, is a clear to yellowish oil obtained from the dried ripe seeds of the flax plant . The oil is obtained by cold pressing, sometimes followed by solvent extraction...

. Earthen plaster is usually applied to masonry

Masonry

Masonry is the building of structures from individual units laid in and bound together by mortar; the term masonry can also refer to the units themselves. The common materials of masonry construction are brick, stone, marble, granite, travertine, limestone; concrete block, glass block, stucco, and...

, cob

Cob

-Places:* Cobb, California* Cobb, California, former name of Pine Grove, Lake County, California* Cobb County, Georgia, United States* Cobb, Georgia, an unincorporated community in Sumter County, Georgia, United States...

, or straw bale interiors or exteriors as a wall

Wall

A wall is a usually solid structure that defines and sometimes protects an area. Most commonly, a wall delineates a building and supports its superstructure, separates space in buildings into rooms, or protects or delineates a space in the open air...

finish. It provides protection to the structural and insulating building components as well as texture and color.

Physical composition

All plaster

Plaster

Plaster is a building material used for coating walls and ceilings. Plaster starts as a dry powder similar to mortar or cement and like those materials it is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after setting,...

s and stuccos have several common features: they all contain a structural component, a binding element, and some form of fiber. Usually the term plaster refers to a wall covering made from earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

, lime

Lime (mineral)

or gypsum

Gypsum

Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...

, while stucco

Stucco

Stucco or render is a material made of an aggregate, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as decorative coating for walls and ceilings and as a sculptural and artistic material in architecture...

uses a cement

Cement

In the most general sense of the word, a cement is a binder, a substance that 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 resembling modern concrete that was made from crushed...

or synthetic binding element.

Clay: the binding agent

Clay

Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...

is a soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

component consisting of extremely fine particles. Most clays consist of hydrous aluminum silicates, though there is a considerable amount of chemical variation among the clays. Clay is cohesive and binds to the sand

Sand

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

and the straw

Straw

Straw is an agricultural by-product, the dry stalks of cereal plants, after the grain and chaff have been removed. Straw makes up about half of the yield of cereal crops such as barley, oats, rice, rye and wheat. It has many uses, including fuel, livestock bedding and fodder, thatching and...

, holding the mixture together, as well as securing the mixture to the wall. Clay

Clay

is also plastic when wet, which makes the plaster mixture workable.

Sand: structural strength

Sand

provides structure, strength, and bulk to earthen plasters. Sand consists of tiny mineral granules of rock

Rock (geology)

In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

, its parent material. Predominately composed of silicon dioxide

Silicon dioxide

The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...

(quartz

Quartz

Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

), sand

Sand

is a non-reactive substance. Because sand

Sand

occurs naturally in many subsoil

Subsoil

Subsoil, or substrata, is the layer of soil under the topsoil on the surface of the ground. The subsoil may include substances such as clay and/or sand that has only been partially broken down by air, sunlight, water, wind etc., to produce true soil...

s, all of the sand

Sand

necessary may be already found in the clay

Clay

Fiber: tensile strength and reinforcement

Dry straw

Straw

, hemp

Hemp

Hemp is mostly used as a name for low tetrahydrocannabinol strains of the plant Cannabis sativa, of fiber and/or oilseed varieties. In modern times, hemp has been used for industrial purposes including paper, textiles, biodegradable plastics, construction, health food and fuel with modest...

fiber, catails, coconut

Coconut

The coconut palm, Cocos nucifera, is a member of the family Arecaceae . It is the only accepted species in the genus Cocos. The term coconut can refer to the entire coconut palm, the seed, or the fruit, which is not a botanical nut. The spelling cocoanut is an old-fashioned form of the word...

fiber, and animal hair are all suitable fiber choices for earthen plasters. Fiber forms a reinforcing meshwork in plasters, which helps to hold the plaster together. Fiber also provides some flexibility to a dried plaster. When Clay

Clay

dries it shrinks and tends to crack, but this cracking can be countered by the fiber. The fiber used in plasters must be clean, dry, and mold-free.

Additives

Additives are usually blended with the clay

Clay

, sand

Sand

, and natural fiber

Natural fiber

Fibers or fibres are a class of hair-like materials that are continuous filaments or are in discrete elongated pieces, similar to pieces of thread. They can be spun into filaments, thread, or rope. They can be used as a component of composite materials. They can also be matted into sheets to...

to improve the workability and strength of a plaster. Sometimes additives are added to the finish coat and other times additives may be added to all coats. Some of the most common additives are wheat flour paste, manure

Manure

, cactus juice, casein (milk protein) and various natural oils such as linseed oil

Linseed oil

. Other additives include, salt

Salt

In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

, sterate, tallow

Tallow

Tallow is a rendered form of beef or mutton fat, processed from suet. It is solid at room temperature. Unlike suet, tallow can be stored for extended periods without the need for refrigeration to prevent decomposition, provided it is kept in an airtight container to prevent oxidation.In industry,...

, tannin

Tannin

A tannin is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids.The term tannin refers to the use of...

, leaves

Leaves

-History:Vocalist Arnar Gudjonsson was formerly the guitarist with Mower, and he was joined by Hallur Hallsson , Arnar Ólafsson , Bjarni Grímsson , and Andri Ásgrímsson . Late in 2001 they played with Emiliana Torrini and drew early praise from the New York Times...

and bark

Bark

Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner...

of certain trees, xanthum gum, alum

Alum

Alum is both a specific chemical compound and a class of chemical compounds. The specific compound is the hydrated potassium aluminium sulfate with the formula KAl2.12H2O. The wider class of compounds known as alums have the related empirical formula, AB2.12H2O.-Chemical properties:Alums are...

, natural glues, gum arabic

Gum arabic

220px|thumb|right|Acacia gumGum arabic, also known as acacia gum, chaar gund, char goond, or meska, is a natural gum made of hardened sap taken from two species of the acacia tree; Acacia senegal and Acacia seyal...

, kelp

Kelp

Kelps are large seaweeds belonging to the brown algae in the order Laminariales. There are about 30 different genera....

, lime

Agricultural lime

Agricultural lime, also called aglime, agricultural limestone, garden lime or liming, is a soil additive made from pulverized limestone or chalk. The primary active component is calcium carbonate...

, powdered milk

Powdered milk

Powdered milk is a manufactured dairy product made by evaporating milk to dryness. One purpose of drying milk is to preserve it; milk powder has a far longer shelf life than liquid milk and does not need to be refrigerated, due to its low moisture content. Another purpose is to reduce its bulk for...

, or the blood

Blood

Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

of livestock.

Flour paste

Cooked flour paste is an a cheap natural glue

Glue

This is a list of various types of glue. Historically, the term "glue" only referred to protein colloids prepared from animal flesh. The meaning has been extended to refer to any fluid adhesive....

that is easy to make from common ingredients. The water and flour

Flour

Flour is a powder which is made by grinding cereal grains, other seeds or roots . It is the main ingredient of bread, which is a staple food for many cultures, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history...

slurry is cooked until the gluten binds the elements of the mixture, creating a durable glue. In plaster, the flour paste serves as a binding agent and a hardener.

Manure
Manure
Manure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil...

Manure

serves as a binding agent and gives plaster more body. Manure

Manure

also contains small natural fiber

Natural fiber

s that provide additional tensile strength

Tensile strength

Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...

as well as reduce cracking and water erosion. Different types of manure

Manure

have different effects. Horse manure has a high microfiber content, but cow manure has more hardening enzymes. People have reported success with llama

Llama

The llama is a South American camelid, widely used as a meat and pack animal by Andean cultures since pre-Hispanic times....

and alpaca

Alpaca

An alpaca is a domesticated species of South American camelid. It resembles a small llama in appearance.Alpacas are kept in herds that graze on the level heights of the Andes of southern Peru, northern Bolivia, Ecuador, and northern Chile at an altitude of to above sea level, throughout the year...

dung. Manure

Manure

should be as fresh as possible when mixed with plaster, as composted manure loses its enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s and adhesive qualities. Manure

Manure

should be sifted before use.

Prickly pear cactus juice

The liquid from prickly pear

Opuntia

cactus is one of the most common additives. Prickly pear is one of the most prevalent species of cactus

Cactus

A cactus is a member of the plant family Cactaceae. Their distinctive appearance is a result of adaptations to conserve water in dry and/or hot environments. In most species, the stem has evolved to become photosynthetic and succulent, while the leaves have evolved into spines...

in the world.

Interior earthen plaster

Pure earthen plaster (plaster without lime, cement, or emulsified asphalt) is applied to interior surfaces more frequently than exteriors. Before the plaster can be applied, it must have a surface to bind to. Many types of wire mesh may be used, such as expanded-metal lath, woven wire lath, or welded wire lath. Reed mats are another option. If the plaster is being applied to a smooth surface such as drywall or plywood, a mixture of sand and wheat paste may be painted on to the surface to create the texture needed for plaster to bond.

The plaster is usually applied in three coats. The first layer of plaster is called a "scratch coat". A "comb" is used to scratch the surface horizontally or in a crisscross pattern to provide a key for the second layer. In the United States, the "comb" is commonly referred to as the "scratcher". The next layer is called the "brown coat" or leveling coat. It is leveled with tools called "Darbys" and "Rods", scraped smooth, and floated to provide a nice even surface onto which to apply the color coat. It is then allowed to dry (cure) for 7–10 days minimum to allow "checking" (shrinkage) to take place. The final layer is referred to as the "color coat" or "finishing coat", and is typically 3 mm (1/8") thick. It usually consists of clay with no fiber and little added sand. Coloring pigments are often added.

Advantages and disadvantages of earthen plaster

Earthen plasters are less toxic and energy intensive than many other wall coverings, which makes them appealing to the environmentally-conscious. Earthen Plasters are also easily repaired and inexpensive. Earth plasters resist water penetration but are permeable to water vapor

Water vapor

Water vapor or water vapour , also aqueous vapor, is the gas phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Under typical atmospheric conditions, water vapor is continuously...

. However, earthen plasters are often more labor-intensive than other forms of wall covering. If the mix is not correct in component proportions, then many other problems may occur, such as dusting and cracking. Earthen plasters are not approved by all local building codes, as some require the use of cement

Cement

stabilizers or asphalt

Asphalt

Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...

emulsion. Earthen plaster is a rare wall covering in the developed world and there is a dearth of local experts for construction and repair.

Physical composition

Clay: the binding agent

Sand: structural strength

Fiber: tensile strength and reinforcement

Additives

Flour paste

ManureManureManure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil...

Prickly pear cactus juice

Interior earthen plaster

Advantages and disadvantages of earthen plaster

See also

Manure
Manure
Manure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil...