GROWING STONES — A BIOMIMETIC APPROACH

Thanks to digital fabrication, the craft of design and architecture has been steadily moving from creating forms towards designing processes, with an attempt of removing unpredictable natural factors from the act. This in turn leads to a sterile product devoid of organic traits inherent in naturally produced objects.

With the new biomimetic approach, where the imitation of nature is not formal anymore, but simulates the structures, the functions and the processes of the nature, the design aims at creating a symbiosis between the two with the goal of producing new aesthetic values.

The digital fabrication research is often putting attention on programming new materials in different scales or incorporating natural processes to grow more efficient and useful materials. One of such attempts has been the project of a Dutch duo.

The CaCO3 — Stoneware project by Laura Lynn Jansen & Thomas Vailly, was presented in 2014 as a series of tableware made using the natural process of petrification. Their aim was to grow stones on specially designed structures by taking advantage of chemical processes naturally occurring in thermo-mineral springs from limestone caves. The team was inspired by the research of geological processes of petrification in the French region of Auvergne.

So instead of extracting the stones from earth, why not grow them? The team considered the possibilities of aligning their designs with these exogenous processes. [http://vailly.com/projects/caco3/]

After 3D-printing a nylon scaffolding structure, they were placed for a few weeks in thermo-mineral springs of limestone caves with a high content of calcium carbonate (CaCO3) and carbon dioxide (CO2). The amount of time the objects were kept in this environment determined the thickness of the structure, with the final material having properties similar to porcelain or terracotta.

The limestone stalagmites (speleothems) form when there is a certain pH concentration in the caves. The underground water infiltrates the rock, heats up and get saturated with CO2 and different minerals, like calcium carbonate. Then coming out from the wall of a cave, the water is liberating carbon dioxide and goes to form stalagmites or stalactite.

The height of the stalagmites and stalactites is the result of different layers of stratification with long process of steady stream (2mm in 10 years) with cylindrical-conical shapes, due to the water that percolates from the wall and stops on the previous concretion. [https://en.wikipedia.org/wiki/Stalagmite]

The designers of “CaCO3 — Stoneware” didn’t want full control of the final product, but employed the process of random stratification of stalagmites, leaving the skeleton of objects in the caves with the ideas of letting the nature take control of the final result. In this way the colours, the final result of shapes and textures were unpredictable. Similar to how termites form the hollow body of a didgeridoo, the flowing water is the modifying agent for the Stoneware project. The particles in a liquid do not move independently of each other, but neither are they locked rigidly in one position. Because the connections are fluid and complex, the effects of these interactions are unpredictable.

The natural process of stalagmite formation can take years to form a high structure having specific environment requirements. Why not reproduce the same experiments of petrification using an artificial environment where we can control the parameters and make the process faster? In laboratory it’s possible to obtain calcium carbonate through the reaction of calcium oxide and water: CaO + H2O = Ca(OH)2. Then a stream of carbon dioxide CO2 is added and the calcium carbonate is obtained from the reaction: Ca(OH)2 + CO2 = CaCO3 + H2O.

We can also take into consideration the fact that skin oils can alter the surface tension where the mineral water clings or flows, thus affecting the growth of the formation. Oils and dirt from human contact can also stain the formation and change its colour permanently. This can be used as an additional parameter in the process of stone-growing, where people can physically interact with the process thus modifying its shape and colour, creating a more personal piece of artefact.