You mentioned once that you don't recommend rehydrating wine yeast, but I couldn't find a follow-up or reasons why. My supplier in the KC area says they always rehydrate as do most wine yeast packs. I've tried both ways and haven't noticed a difference other than rehydrated yeast usually starts working quicker. I am confused.... Name: Lynn T. State: KS ----- Hello Lynn, There is nothing wrong with rehydrating the dried wine yeast. Just as you have stated, the fermentation will start off more quickly by a few hours. Some winemakers will refer to this rehydration process as waking up the wine yeast. But if someone came up to me and asked, is rehydrating yeast necessary? My answer would be a definite, no. The reason I don't generally recommend rehydrating dried wine yeast in passing is because of the potential for accidentally killing the wine yeast during the rehydration process. We run into this issue quite often, particularly with beginning winemakers. It is usually because the water was way too hot and not checked and controlled with a thermometer, or the dried wine yeast was left in the warm water way too long because they didn't use a timer. Both temperature and time are critical to the rehydration process. Some of the yeast cells will die off while in the warm water, even if the correct temperature is used. If the wine yeast is left in for longer than directed, then an excessive amount of yeast cells will die. If the water is a hotter than directed, then the wine yeast will start dying off faster than the directions intended. Either issue can cause a significant amount of yeast cells to die – potentially all of them. The result is a fermentation that doesn't start at all. The point here is go ahead and rehydrate the wine yeast – your fermentation will start off more quickly and more vigorously – but follow the directions, exactly. That means using a thermometer to get the water to the right temperature and using a watch or timer to make sure your yeast does not have an extended stay in the warm water. If you don't want to bother with rehydrating the dried yeast along with the thermometers and timers, don't worry about it. Rehydrating yeast is not a necessity. Your fermentation will start just the same, but it might take a few more hours to do so. The blog post How To Add Yeast To A Wine Must discusses 3 different methods you can use to add your wine yeast to the wine must. You may want to take a look at this to see which method suits you best. Happy Winemaking, Ed Kraus ----- Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.