Monday, December 18, 2006

Working principle of Caffettiera

After knowing the usage of Caffettiera, the specific Italian Coffee pot, from my previous articles one may get satisfied that they found a cheap and best device which is of much use in our daily life. But those who are of my nature and those who want to look into a greater depth to understand how things work, will be puzzled to know the working principle behind the Caffettiera.

The principle merely involves the steam generation followed by the ejection of the solution with the aid of some nozzle like ejection too.

If anyone has watched the Coffee making with Caffettiera for the first time, then I am sure that one will be really surprised to see, how in a such simple device, the coffee is made in the entirely new way, by filtering against the gravity.

Though this is very common in italy, as the Caffettiera is not known to many in the countries like India, it is normal that one gets amazed. But the working principle involved is better known to all.

As explained in the construction and design features of Caffettiera and the procedure of coffee making with Caffettiera, one can appreciate the use of this simple principle of steam generation and pressurizing process aided by nozzle like ejection.

According to my own understanding of the constructional features of Caffettiera, I found by the geometry of the three pieces of the caffettiera that my assumptions are almost correct.

As usual by the heating process steam is generated. This causes the pressure inside the bottom cup over the existing water surface. The funnel like transition piece has its opening very close to the base of the bottom cup.

Due to the formation of steam, the building up of the pressure occurs and due to the complete sealing of the bottom cup with the top cup, unless there is any problem during which the safety valve operates, the steam has no other way to escape.

So the steam pushes the water which is already at 100°C to the base of the bottom cup, and as the only way to escape is the tubular projection of the transition piece or funnel, extending to the bottom, the boiling water rises through the funnel and mixes with the coffee powder with force. And the coffee is made there between two filtering plates one present in the transition piece and the other at the bottom of the top cup.

As the pressure continues to grow with the continuous heating, the water in the bottom cup will be emptied through the funnel's projection and in turn mixes with the coffee in the funnel and then all the coffee after getting filtered through the two perforated plates starts to rise through the hollow tubular projection in the top cup.

There is some sort of velocity rise of the fluid passing through the top cup hollow projection due to its decreasing cross section like in the nozzle.

So if the reader of this article is a future visitor of italy, then I hope that these four articles on Caffettiera will help him / her to find something to carry to their homes after their visit to Italy.

One more final remark: the same Caffettiera can also be used for making Tea by following the same procedure like that of the Coffee making with the Caffettiera. And the price of caffettiera may vary from 5 € to 20 € depending on the number of cups of coffee that can be made with it, and this in turn depends on the size of Caffetiera.

I personally recommend all the Indian visitors especially this simple appliance and advise them to consider buying a caffettiera which can make three cups of strong coffee, i.e., Caffe normale – Normale, as explained in the previous articles, as in India the coffee is not so strong like in Italy.

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