When flour and water are combined, microscopic yeast organisms will become active and begin a process that eventually makes Chamets. These yeast organisms are found everywhere, they are in water and in flour and in the air we breathe.
According to our Traditions, under normal conditions the yeast requires at least 18 minutes to make Chamets. However, with warmth the yeast will be more active and can make Chamets in less than 18 minutes. This is the meaning of the superior Matzos boasting that they are 18 minute Matza. This means that the production is stopped every 18 minutes and the machinery and working surfaces are thoroughly cleaned before production is resumed.
It must be noted though, that according to Halacha, as long as the dough is being manipulated it will not become Chamets. Thus, as long as the machinery is active the dough it is processing will not become Chamets, no matter how long it takes. So Kosher Matza can also be made without stopping the machinery every 18 minutes.