Vespera - dimmable bedside lamp made of concrete | Handmade in Germany – Handworkz

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What makes our concrete special?

One thing can be said in advance: not all concrete is the same!
Through extensive testing, we have developed the perfect concrete mix for us. Our focus was particularly on developing a high-quality concrete that is impressive in terms of durability and robustness. We also felt a particular need to optimise the concrete mix so that it is waterproof. This has the advantage that we can use the concrete to make flower pots and vases, and it also creates the well-known lotus effect, which allows water to run off the concrete. It also makes cleaning easier because dirt has a harder time "sticking" to the surface. In construction, this is even referred to as "self-cleaning concrete" because, for example, as a facade element, it is cleaned by rain and thus practically cleans itself.
The hydrophobic effect achieved with our concrete is not only created by a simple surface coating, as is often used, but is already anchored in our special concrete recipe. In addition, our concrete not only impresses with its even and smooth surface, but also with a completely colored mass.

A ready-mixed product was out of the question for us from the start, as it leaves little room for adjustment due to the lack of a list of ingredients. So we designed our own concrete using cement, sand and other ingredients.
We started with prior knowledge of the composition of concrete in construction, but determining a concrete recipe for a concrete wall with a thickness of 200 mm is quite different than for a vessel with a wall thickness of 10 mm.
The first and probably easiest step is to adjust the so-called "maximum grain size" to the concrete's grading curve. The grading curve describes the composition of different grain sizes, from sand to gravel in the concrete. In construction, a maximum grain size of 8 mm is usually chosen for delicate components, but in exceptional cases this can be smaller. For thick components, such as foundations, a maximum grain size of 32 mm is often chosen. In general, the larger the maximum grain size selected, the cheaper the same amount of concrete can be obtained. Due to the nature of the component, however, it is not always sensible to choose the largest possible grain size. This becomes clear when you concrete a container with a wall thickness of 10 mm with a maximum grain size of 8 mm. It will just about fit in, but when processing it, you will very quickly notice that the individual grains wedge together and the mold is not filled properly. To avoid this, we use a maximum grain size of 2 mm for most of our products, but we reduce the grain size to less than 1 mm for some very delicate pieces to achieve even better results.
But this only lays the foundation for the concrete recipe, as the maximum grain size only describes the dimensions of the largest grains. However, it is very important to incorporate the right mixture of different grain sizes in the range of 0 - 2 mm into the recipe, as this is the only way to create the densest concrete matrix possible.

In the construction industry, people often talk about waterproof concrete (waterproof concrete). This is often used for basement walls or other components that are in direct contact with moisture or water. A basement made of waterproof concrete is then referred to as a white tub.
As the term "WU" suggests, no water can penetrate through the concrete, but water can penetrate to a certain depth of around 10 - 20 mm. This works very well in construction due to the greater component thicknesses, but with our delicate vessels we do not have the leeway of 10 - 20 mm. We were therefore forced to create a structure that was as dense and hydrophobic as possible in order to repel any water at the outermost layer.

This extremely dense structure is known in the construction industry as high-strength concrete. Examples of applications include bridges, high-rise buildings, dams, etc. Here, relatively delicate structures are created using high-strength concrete, which are extremely resilient to chemical or mechanical influences.

In conclusion, we have taken high-strength concrete from construction and adapted it to our needs without minimizing its enormous strength, resistance or durability.