Chemical Applications: The Chemical Gardens

by Katrina Hermanns


Although I’m sure we are all focused on the next unit, this is a really interesting
combination of art and chemistry!
Recently, in Germany an artist by the of Tobias Cohlmer opened an exhibition that  features Chemical Gardens “grown” to look like a garden from the future. This chemistry based process was first described in 1646 by chemist Johann Rudolf Glauber and is now being used to create some awesome art.
Each “piece” consists of a large glass tank filled with distilled water and a thick layer of sodium silicate at the bottom. Two thirty-five watt Xenon lights, which are high intensity, are then placed above the tank. Different transitions metal salts are then added to the water filled tank, and once they sink to the bottom the magic begins! Each salt produces a different coloured plant, depending on how it reacts with the water and sodium silicate solution.
In the video below, you can see that even though the labels of each substance are in
Germans, the common hazard symbols are still used.
See the process of making each piece below:



For example, lets use calcium chloride . As the crystals reach the bottom of the tank and start to dissolve, the metal ions combine with the silicate ions to form an insoluble and semi-permeable membrane of calcium silicate around each crystal. Water then diffuses through the membrane in an attempt to balance the high salt concentration inside the membrane, causing pressure to build up. Eventually enough pressure is built up that the membrane ruptures, causing the salt solution inside the cell to shoot upwards. As the solution moves upwards, more membrane it formed around the moving salt solution, trapping it inside the membrane once again and creating growth in the structure. The process then continuously repeats itself.




The combination of the insoluble membrane, and hollow, solution filled tubular structure of these “plants” is what allows them to not only physically appear like sea flora, but actually move within the water’s current like water plants do as well.
The Xenon lights placed above the tank don’t have an affect on the reaction process that
creates the “plants”, but are rather used to help Cohlmer document the process of his  work. Xenon lights in particular produce short but intense burst of light, which are ideal for special effects or producing high quality photographs. By placing the lights above the tank, Cohlmer eliminates the need to use the flash on his camera, which would interfere with the glass tank and ruin his photographs.
By using combinations of calcium chloride, copper (II) sulphate, iron (III) chloride, chromium (III) chloride, iron (II) sulfate and manganese (II) chloride (just to name a few!), Tobias Cohlmer has found a way to use chemistry in the creation of his stunning artistic expressions, which capture the attention of not only chemists and scientists around the globe but the art community as well.