Hold an instant-read thermometer under running water to find correct temperature. If the water is cold, the yeast will stay inactive and if it is too hot, the yeast will die. In a small bowl, add the amount of water called for in your recipe.

Measure out the yeast and add it to the water. Whisk to completely dissolve the yeast. If there is sugar in your recipe, add a pinch to the water. Adding the sugar will give the yeast something to eat and will speed up the process.

Wait 10 minutes. If the yeast is alive, it will form a bubbly crust as it eats the sugar and gives off gasses. If nothing happens, your yeast is dead. Do not proceed with dead yeast because your recipe will fail.