The concern that a moka pot could explode arises from the fear that the pressure could build up to the point of causing a violent rupture, as happens in the case of some explosives, but on the basis of the few existing experimental studies, generally, a moka used correctly does not explode. The pressure that develops when we use it is relatively low and, especially in the most modern coffee makers, there are safety devices that limit the accumulation of energy. This doesn’t mean that nothing serious can’t happen or has never happened, on the contrary. Dangerous events can occur when the “correct” procedure that leads to our espresso coffee is not applied 100%: a blocked internal channel or the failure of the safety valvefor example. The moka is not a bomb, but like any system that works with heat and pressure it can become dangerous if used incorrectly or neglected. In any case, based on the experimental pressure data, if something went wrong we should not witness a real explosion, but at most a sudden release of steam and hot liquid.
The pressure that develops is too low
The moka uses a simple but precise thermodynamic process studied ad hoc. Once the flame is lit, the water contained in the lower boiler heats up and begins to produce steam, which causes an increase in internal pressure. Thanks to pressure boostthe hot water manages to rise through the filter containing the ground coffee to the upper chamber. During this step, the heat of the water allows the extraction of soluble substances, responsible for the aroma and flavor of coffee), transforming water into the well-known and appreciated drink. If the flow is free, the pressure does not increase beyond certain values e everything goes smoothly.
An experimental study states that i pressure values typical developed inside the moka in general do not exceed 1-2 bar (100-200 kPa), much lower than those typical of domestic pressure cookers, and this alone reassures us.
What could be the (unlikely) causes of the mocha explosion?
There are no scientific studies who state with certainty that explosions cannot occur, but on the basis, for example, of the pressure values calculated in the previous study, it is reasonable to say that an explosion is very unlikely.
The problem could arise when the system is no longer able to release the pressure. In sparticular situationsthose pressure values can certainly rise, but not enormously. In that case, the main risk should not be an actual explosion, but the sudden release of warm fluid. It’s the same principle as a closed bottle left in the sun: it doesn’t “explode” like a bomb, but it can open abruptly, spraying liquid, especially if carbonated.
This can happen, for example, if the coffee is ground too fine, if the filter is clogged or if the safety valve is not working properly. Also forget to add water or leaving the moka on the stove for a long time can lead to very high temperatures and pressures, capable not only of burning the coffee, but also of seriously damaging the coffee maker.
This does not mean that we should underestimate the risk – we are still talking about an object that works with heat and pressure, two ingredients that, if handled poorly, can become dangerous – but we certainly shouldn’t be alarmed by thinking of one of the most classic movie explosions.
How to reduce risks: maintenance and attention
To further reduce any risk simply follow the correct procedure of coffee preparation: water added without exceeding the indicated level, unpressed coffee and adequate grinding.
Furthermore, it is important to combine these good practices with some prevention: regular cleaning, filter control and pay attention to the general condition of the moka. In other words, respect for basic rules and common sense. In essence, unpleasant and potentially risky events can happen, especially in case of incorrect use or poor maintenance, but a real catastrophic explosion is to be ruled out in the vast majority of cases.
