''Tadelakt'' () is a waterproof

plaster Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "re ...

surface used in

Moroccan architecture Moroccan architecture refers to the architecture characteristic of Morocco throughout its history and up to modern times. The country's diverse geography and long history, marked by successive waves of settlers through both migration and militar ...

to make baths, sinks, water vessels, interior and exterior walls, ceilings, roofs, and floors. It is made from

lime plaster Lime plaster is a type of plaster composed of sand, water, and lime, usually non-hydraulic hydrated lime (also known as slaked lime, high calcium lime or air lime). Ancient lime plaster often contained horse hair for reinforcement and pozzolan ...

, which is rammed, polished, and treated with soap to make it waterproof and water-repellant. ''Tadelakt'' is labour-intensive to install, but durable. Since it is applied as a paste, tadelakt has a soft, undulating character, it can form curves, and it is seamless. Pigment can be added to give it any colour, but deep red is traditional. It may have a shiny or

matte Matte may refer to: Art * paint with a non-glossy finish. See diffuse reflection. * a framing element surrounding a painting or watercolor within the outer frame Film * Matte (filmmaking), filmmaking and video production technology * Matte pa ...

finish.

Etymology and history

The term ''tadelakt'', meaning "to rub in", is an Amazighified expression from the

Arabic Arabic (, ' ; , ' or ) is a Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C. E.Watson; Walter ...

word , meaning "to rub or massage." ''Tadelakt'' is thought to have evolved from ''

qadad ''Qadad'' ( ''qaḍāḍ'') or ''qudad'' is a waterproof plaster surface, made of a lime plaster treated with slaked lime and oils and fats. The technique is over a thousand years old, with the remains of this early plaster still seen on the st ...

'', a similar plaster used in Yemen for millennia that is treated with calcium hydroxide and oils and fats instead of soaps.Anita Sutter, « Note sur la fabrication du qadâd », Chroniques yéménites n ligne 6-7 , 1999, mis en ligne le 18 décembre 2006, consulté le 13 février 2016. URL : http://cy.revues.org/111

Constituents and chemistry

The basic constituents of ''tadelakt'' plaster are: # lime plaster (not Portland cement) # in some cases, marble or limestone sand (but not other aggregates) # natural soap (often "black" or olive oil soap) to speed

carbonation Carbonation is the chemical reaction of carbon dioxide to give carbonates, bicarbonates, and carbonic acid. In chemistry, the term is sometimes used in place of carboxylation, which refers to the formation of carboxylic acids. In inorganic ch ...

of the surface and impart water-resistance. The soap chemically reacts with the lime plaster, forming lime (calcium) soaps. Calcium soaps are insoluble in water, and fairly hard. They are familiar, in areas with calcium-rich ("hard") water, as deposits in bathtubs, sinks, and showers; when soap is mixed with the water's dissolved calcium carbonate/lime, calcium soaps form. :2 C₁₇H₃₅COO⁻Na⁺ + Ca²⁺ → (C₁₇H₃₅COO)₂Ca + 2 Na⁺

Techniques

Traditional application includes polishing with a river stone and treatment with

oleic acid Oleic acid is a fatty acid that occurs naturally in various animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish. In chemical terms, oleic acid is classified as a monounsaturated o ...

, in the form of olive oil soap, to lend it its final appearance and water resistance. In Morocco, the traditional application technique: * plaster powder is mixed with water for 12 to 15 hours prior to the addition of pigment. * the plaster is applied in one thick coat with a wooden float, and smoothed with the same. * before the plaster sets, a flat, smooth, hard stone is used to compress the plaster, then a plastic trowel used for the final polish. * it is mechanically polished using stones or abrasives harder than the plaster, providing a smooth, sometimes shiny, finish. * lastly, an olive-oil soap solution is used to seal the plaster Long-term maintenance of tadelakt requires regularly re-sealing the surface with a soap solution; in the case of

roofs, this was traditionally done every few years.

Uses

''Tadelakt'' is the traditional coating of the

hammam A hammam ( ar, حمّام, translit=ḥammām, tr, hamam) or Turkish bath is a type of steam bath or a place of public bathing associated with the Islamic world. It is a prominent feature in the Islamic culture, culture of the Muslim world and ...

s and bathrooms of palaces and riad residences in

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to A ...

. The restoration of riads in Morocco has led to a resurgence in its use. In modern times, it has been used outside.

References

External links