The Basics - Proofing Yeast for Bread Making
This basic step is vital to successfully baking bread. The first step in any bread recipe (or some other yeast dough recipe) calls for proofing or activating the yeast. This is the step where you mix sugar, dry yeast and either hot water or hot milk (about 110 degrees). The reason for this step is not only to activate the yeast but also, (if it is old yeast) this step will save you from possibly wasting your time and ingredients. Old yeast will not activate, therefore your bread will not rise.
Allow the yeast mixture (sugar, yeast & water/milk) to "proof" for 5 to 10 minutes. You will notice that the yeast granules disappear and the mixture will become frothy, bubbly and foamy (see pictures). If this foamy/frothiness does not happen then your yeast is old and you must throw the yeast mixture away and start the "proofing" process over with new yeast.
NOTE: I have a candy thermometer that I use and I tested my hot tap water - it is exactly 110 degrees at it's warmest temperature. So, if you do not have a thermometer, then most likely your hot tap water will be warm enough to "proof" the yeast. (Careful - if the liquid is too warm then that will also stop the yeast from activating)