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Don't know how to please Your loved one on st. Valentine's day?

Aktualisiert: 6. Apr. 2021

We made a chart of possible gifts for your dearest one on this event.

It is a summary of the most common practices with its PROs and CONs.

What is Vera, the concrete vase?

It is a result of a unique collaboration with academic sculptor Veronika Durová.

The manufacture of the concrete vase

In the beginning, we had a model. Unfortunately, it was a solid mass, without any intestines to put the flower in. We had to develop a method, how to tunnel a hollow space through the aortas and arteries, to make it possible to use the statue as a vase

That turned out to be quite an issue because to do that, we needed a second model to hold the hollow shape while pouring the concrete. Also, it was important to place the inner model exactly in the centre of arteries, so that the side thickness of arteries would be the same all around.

Especially interesting was to think about the right material to create an inside model from. We came up with a technique of paraffine tunnelling.

The paraffine tunnelling technique

Our goal was to empty the space of the inside model so that we will have only the concrete shell. There were not many options. We chose the paraffine model. From the original model, we cut out the inside one and make sure it is exactly in the centre of the arteries, which will work as a hole to put the flower in.

A fitted paraffine model was then coated in concrete and left to mature for 3 weeks. It is extremely important to let concrete mature enough to strengthen its inside bonds and therefore being able to withstand the pressure of enlarging wax in the following critical phase of production, which will deeply test its quality.

After a thorough maturing phase it is time to get rid of wax from inside the vase. To create a paraffine tunnel. That is possible only by melting. There are two ways, how to melt the wax, chemical way and thermic way. Both come with pros and cons.

Chemical way

+ Pros

+ No risk of thermic rupture due to volume expansion

- Cons

- Ecologically unfriendly - Takes ages - Hard to recycle the residuum - Costly

Thermic way

+ Pros

+ cca 95% paraffine could be recycled + Ecologicaly friendly + Automatically impregnates the concrete from inside + Relatively fast

- Cons

- High risk of thermic rupture due to volume expansion - Risk of overall thermic damage to concrete

We chose the Thermic way. Even that could be done in two ways, wet and dry way. Dry melting might be clearer, but you need to hold the temperature low and stable for a long period.

In this case, a wet way has much more benefits.

Separation of paraffin hydro-thermal way

We put matured cast to a water bath and slowly started to increase temperature. The temperature had to be at least 42°C and must not exceed 65°C. Water will slowly temper the concrete shell and start to melt the wax. If the temperature rises too fast, there will be parts of still solid (cold) wax blocking the way to release the pressure and the heart will crack. On the other hand, if the temperature is too low the whole mass will be tempered, but the wax on the sides will not be as liquid as it needs to be to escape. And crack might come again.

Here is a schematic workflow. First, we applied it inside the wax model, then we let it mature and after that heat it up in a regulated water bath. Since water is heavier, it will apply pressure to liquid wax and force it to move upwards, while taking its place. The higher the water cylinder above the model is, the higher the pressure is applied and the better the result might be.

After cooling down, the wax, floating on the very top of the water surface will freeze into the wax lid. Underneath the lid is the concrete shell in clear water. Great about this technique is, that surface of the shell, where the wax model touched it is now deeply impregnated by melted wax and therefore waterproof. Now we just need to move on some final touches and we are done.

Not all of the vases "survived"

As you might guess, the development required some sacrifices. Almost half of the first batch fell on the altar of science and ruptured. It was mainly due to a rupture in the tricuspid valve. The complexity of the whole process and thy symbolics of broken heart led us to try to find a way, how to save even the broken hearts, rather than just toss them away as useless shards.

Therefore we decided to give a chance even to broken hearts and restored them by Japanese technique kintsugi. But that is a different story, for a different post. Subscribe to our newsletter, not to miss any news!

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