Originally Posted by toddrod
Here is a question that I just thought of. What is the correct way to figure out the residual sweetness of a wine before it is fermented?
Could I take an alcohol potential reading from my hydrometer and substract the alcohol tolerance of the yeast strain I will be using? The reason I am asking is that I can not stand a dry wine. All my wines are semi-sweet or sweet. I would rather not back sweeten at the end of fermentation if possible.
In theory, your idea will work. However, it's not always that predictable. Sometimes a yeast that is listed at 14% tolerance will have a happy fermentation that will go easily to 15-16% so you still may have a dry wine that is "hot". Some people have found that adding sugar at the end of the fermentation helps to overcome the yeast and give a sweet finish.
I don't know why you wouldn't want to sweeten at the end, but if you want to try to get a yeast that finishes at a lower ABV and give it a try, it might work for you. I find that it's more dependable to allow the fermentation to finish up, stabilize it and sweeten it to exactly where I want it.