Hydrometer Question- OG

[mammachick]

I read that the batch needs to be tested for original gravity BEFORE the yeast is added. I of course added yeast and now have decided on this my 5th 1 gallon batch that I would like to know the alcohol content. Just got this batch in the carboy minutes ago. Can I still do an accurate OG reading?

 

[doug293cz]

I read that the batch needs to be tested for original gravity BEFORE the yeast is added. I of course added yeast and now have decided on this my 5th 1 gallon batch that I would like to know the alcohol content. Just got this batch in the carboy minutes ago. Can I still do an accurate OG reading?

Yes. The sooner, the better. Once fermentation takes off, the SG starts dropping fairly quickly. Before things get going, SG won't change.

Brew on

 

[mammachick]

Follow up question:
If i add addition sugar at an point in the process before taking the FG will my results be accurate? I am a newby, so I apologize if this is a dumb question.

I added sugar to a batch of blackberry hard cider the other day so now I am wondering if my final test will be correct.
Thanks!

 

[m00ps]

Use a brewing calculator online to determine how much points to the OG the sugar will add based on your batch size. If I remember right, like 1lb of cane sugar adds +0.009 to the est OG and +0.002 to the est FG for a 5gal batch

 

[GilSwillBasementBrews]

I didn't think sugar would add anything to the FG as it is 100% fermentable. I believe it will cause the FG to be lower due to higher alcohol level. I could be wrong though and will be corrected if so.

 

[bernardsmith]

I don't think the addition of sugar makes the final gravity lower. Fruit ain't grain, and fruit must ain't wort. All fruit sugars are more or less 100 percent fermentable, so you should expect the final gravity to be below 1.000 (the gravity of water) since alcohol is less dense than water. The addition of sugar will increase the potential ABV (alcohol by volume) as you have for all intents and purposes increased the STARTING specific gravity, not the final gravity.

Assuming that you are using an appropriate yeast (ie one that won't croak because of alcohol poisoning) then adding sugar after you have pitched the yeast simply means that you add the increase in SG to the starting SG to determine the potential ABV. ( 1 lb of sugar added to make 1 gallon of must will increase the gravity by about 40 points or 0.040 and 40 points of gravity will result in an increase of about 5% ABV)

If the OP knows the source of the juice (and if that juice was commercially made and sold ) then it is easy to figure out the sugar content (it will be on the label).
If the source was not labelled then you can likely assume that fruit juice at normal dilutions will have a gravity of about 1.045 - 1.050.
If we know the measured sugar content of the juice then we can calculate the starting gravity and if the OP knows the weight of the additional sugar that was added then we know the potential ABV and his/her hydrometer can then easily track where in the process the fermentation is ...