Question on figuring out % alcohol

Hey Rusty - Did you not take a hydrometer reading of the complete must including any sugar you added before adding the yeast? If you don't have a starting specific gravity you won't be able to estimate the alcohol content of the dry, finished wine. If you do have a starting SG report back and we can calculate a potential alcohol content. There's been a ton of discussion about the subject of alcohol content and how to measure or estimate it but you do need a starting SG.

Bill Frazier Olathe, Kansas USA

It is sometimes instructive to know what the gravity is when you rack but if it is actively fermenting and healthy I never bother. To figure alcohol %abv you need 2 readings. The starting SG which is taken before fermentation begins and the ending fermentation which is taken when all fermentation has ended. The difference between these is the drop in SG and that is what is generally used to determine % alcohol.

Now for the exception. If you add any sugar during fermentation, then you must account for that by noting the SG before you add the sugar and the SG after you add the sugar so you can adjust your final readings by this addition.

Now for exception number 2. When you make fruit wine, not all sugar in the fruit will go into solution when you first mix up your batch. This can cause an error on your calculation. You may have to determine what the average sugar content of the fruit you are using is expected to be and adjust for that. With cranberries -- forget it. No adjustment.

As you might guess, alcohol calculation is seldom made accurately. It is at best a guestimation rather than a calculation. You will probably be within a percent or 2 plus or minus.

Ray

I agree with Ray. Like he says, there isn't much sugar in Cranberries. Presumably then you added sugar before or during fermentation. You can get a good estimate of alcohol then based on how much sugar per gallon was added. If you started with sweetened cranberry juice then it's a different story. You can however get a sample of the juice and measure its SG to get an estimate of how much sugar the manufacturer added.

By and large you take the SG prior to adding yeast. You measure during fermentation to decide when to rack but I also don't do that. I use the activity in the air lock to determine when. I rack when the vigor is gone but before it's quite done. Then at the end to assure it really is done fermenting. I find my taste buds make another good barometer for completion since in certain conditions the ferment can get stuck. If it tastes sweet then it's probably not done. If you're after a sweet wine then you'd better add sorbate if you want to block any more fermentation.

One more thing, it's hard to measure SG when there's active fermentation because bubbles of CO2 quickly form on the gizmo causing it to rise. I spin it to knock the bubbles off and then take a quick reading.

Chris