After 5 minutes, you should notice indications of life. The yeast should be frothy, bubbling, and growing after 10 minutes. It should have grown to cover more than half of the cup/jar and smelled yeasty. The yeast is dead if it does not bubble, froth, or respond. If this happens, start over with new yeast. Yeast can fail for many reasons. Some common causes include: Lack of nutrients in the water. If the water was not aliveic, then the yeast won't be able to grow. You should try a different source for your water. If it isn't drinkable, then don't use it for anything else! Too much heat. If the water was hot enough to kill all the bacteria that would otherwise help ferment the wort, then the yeast will die too. Try using lukewarm water instead. This reduces the risk of killing off some of the good bacteria in the mash while still allowing the yeast to grow and produce alcohol. Incorrect temperature. If the water was cool enough to slow down the yeast growth but not cold enough to kill it completely, then they will grow but not as fast as they should. You should try warming the water slightly before adding it to the mash to increase the rate at which the sugars in the malt are converted into alcohol and carbon dioxide. Out of business.