Tadelakt hi(story)

A few days ago I received the following email that left me stunned: “We are a couple from xxx who travelled to Morocco and fell in love with the culture and much of the Berber craftsmanship. After some research we realised that the material used in some riads is not microcement but Tadelakt.” Microcement marketing will be delighted! WoW!

It is said that Tadelakt has its origin in Marrakech, but that is probably only half the truth. Marrakech was a tent city without walls until the 6th century. The beginning of construction work in Marrakech dates back to the time when the Roman presence in Morocco ended. It is more likely that there was (also) during the Roman presence in Morocco a lively exchange of workers, construction techniques and material science and that locally adapted characteristics developed.

If you visit the lime kilns in the area around Marrakech these days, you won’t miss much of being transported back to ancient times.

The limestone used is interspersed with clay and little stones. The clay gives the lime some hydraulic properties, but since firing in the primitive kilns never reaches temperatures above 950ºCelsius, the hydraulic properties are rather weak. This is also confirmed by its characteristic solidification during processing and because it only hardens very slowly when stored under water.

Tadelakt is hardly an independent technique; it is too similar to what is already known, like the classical Marmorino and stucco techniques that the Romans used “since antiquity”. the two-layer wet-on-wet processing of the lime mortar (hydrated lime, not hydraulic lime), the compacting and polishing… Of course, the processing was adopted to the locally given material and tool conditions.

Nevertheless, the original Marrakech Tadelakt lime and its processing have characteristic features that are unique. The first thing you notice is that Marrakech lime is much coarser than hydrated lime usual is. This has to do with its incomplete slaking, which is only done superficially with a garden hose after the stones come out of the kiln. The color varies in all shades of cream, white Marrakech lime is rare and sought after. The contamination of the lime powder is high, small stones are encountered again and again during processing, the sieving was only done very roughly. The reactivity of lime decreases rapidly as storage time increases.

Because the material is so coarse, it is automatically applied thicker, approx. 5mm per layer. Each of both layers must be carefully rubbed with a wooden float to grind down the lime grains. The freshly ground lime grains give the layer new strength. The final strength is comparable to that of a highly hydraulic lime. The surface is compacted and polished gradually using a steel trowel (didn’t have one before) and a flat-ground granit river pebble. The water resistance is only achieved completely the next day with an extensive surface massage with olive soap.

In this context it is also interesting to note that comparable techniques of final polishing with a river pebble are also known from Africa and South America. Here, the thin, last clay layer of the exterior plaster was polished and compressed with river pebbles to better withstand the weather.

Nowadays, real Tadelakt is a labour-intensive luxury that -outside from Marocco- is only be performed by a few specialists. The unprotected name “Tadelakt” is often misused for micro-cement and other pseudo-products. Traditional lime pressing techniques such as Tadelakt and Marmorino consist exclusively of (weakly hydraulic) hydrated lime, limestone powder and clay impurities which, in the case of Marrakech lime, provide for weak hydraulicisation. In contrast, microcement, Mortex and other one-component finished products marketed under the unprotected names of “Tadelakt”, “Marmorino” or “Stucco Veneziano” are largely cement- and acrylic-based.

Original Marrakech lime is used outside Marocco only in exceptional cases because the quality of the material varies greatly, can only be imported in large quantities for which there is no market, and the import is energy and time-consuming.

The processing also differs enormously. Traditional lime press techniques are only compacted with steel trowels, never sanded. If microcement and similar applications cannot do without a final varnish, a final oil or wax treatment of lime press techniques is technically not necessary. Since ancient times, fresh lime surfaces have been treated only with olive soap and have been handed down to us for centuries as pleasing frescos, marmorinos, stuccos and Tadelakt.

Tadelakt is waterresistant -not waterproof- and is best suited for outdoor use and showers, but only if used carefully and maintained regularly. Anyone who uses Tadelakt for surfaces that constantly come into contact with water must impregnate the surfaces regularly, otherwise the fine lime particles on the surface will be washed out. Once the surface is roughened, it needs to be repaired. I do not use Tadelakt on work tops and floors because the necessary abrasion resistance and shock proof is missing.