3. Detergency mechanism

The diagram at 6 shows that water, which has a surface tension of around 70 dynes, will have difficulty penetrating a crack. Beer, on the other hand, with a surface tension of around 55, will be able to penetrate deeper into the crack. A good detergent with a surface tension of between 30 and 40 dynes will penetrate deeper and dislodge any impurities lodged there. On the other hand, the rinsing water will not be able to remove any remaining detergent from the crack.