Cider ABV

Hey guys,

This is my third attempt at a hard cider. I believe I over fermented the primary as I got a final gravity of .998 after have an OG of 1.068. I was kind of excited because the ABV of this cider was 9.3%. I figured that after back sweetening the cider with apple juice and a cinnamon caramel sauce it would be some where around 6 or 7%. I took a reading the other day and it came out to be about 4.3%. Why would it be such a low ABV after starting with such a difference of OG to FG?

Just for clarification i started with 3 gallons of apple juice added 1lb of dextrose and yeast nutrient. To back sweeten I used 2 cans of apple juice concentrate, and caramel sauce made from 1 cup water, 1 cup brown sugar and 1 tbs apple pie spice.

Shouldn't I have had a higher ABV?

Sounds like you may not be understanding the use of the hydrometer.
Not quite sure what you’ve done but here’s two random pointers ... when using the hydrometer you can’t just put it in the sample and read the “ABV%” reading on the side of the bulb-stem - there is additional math involved ... point #2 - when you added the backsweetening you skewed the accuracy of any “current gravity” reading because you’ve manually changed the brix.
Probably need to read up on the use of the device and the math.

A “back of the cocktail napkin” figure ... In general, if you had 3 gallons of 9.30% abv and further diluted the volume with approximately 24oz of concentrate, 8oz of water and another 5 oz or so of sugar (5 oz by volume displacement) ... you’re ABV would drop from 9.3 to something around 8.4 to 8.6% ABV.

To add to the confusion sugar will actually absorb and fill in the empty spaces in molecules causing less than the 5oz displacement for adding 5oz of sugar.

Hence why its really only an estimate...

So I may not have filled in all the details. I took the original gravity with a hydrometer and then in my infinite wisdom, shattered it. I went to replace it and decided to try a refractometer instead. In talking with another brew buddy he stated that the refractometer is going to be skewed because I had liquid, alcohol and sugar all bending the light and not just the liquid and alcohol. When figuring the abv of all my other brews, I generally just take the OG and the FG and then use an online calculator to figure the abv for me. I used the two measurements and plugged them into the website and came up with the 4.2%. I didn't really figure that was accurate but wasn't sure why. Is there somewhere that easily explains how to accurately calculate abv with the numbers from the hydrometer. I will be replacing the broken hydrometer and use both until I get comfortable with the refracometer.

johnsonbrew said:

So I may not have filled in all the details. I took the original gravity with a hydrometer and then in my infinite wisdom, shattered it. I went to replace it and decided to try a refractometer instead. In talking with another brew buddy he stated that the refractometer is going to be skewed because I had liquid, alcohol and sugar all bending the light and not just the liquid and alcohol.

Click to expand...

Yep. With a refractometer, alcohol refracts differently than sugar and so that’s why you use a calculation to adjust when you are testing anything other than pre-fermentation ... reduction in brix causes a decrease in the refractive index while at the same time the alcohol causes an increase.

Nothing like a nice large hydrometer.

johnsonbrew said:

... Is there somewhere that easily explains how to accurately calculate abv with the numbers from the hydrometer.

Click to expand...

Calculating ...
(Original Gravity – Final Gravity) X 131 = ABV%

That said ... alcohol production is not a linear function, and so there is a bit of a slide in the “131” figure depending on where your OG was ... but for our purposes I’d think 131 is fine ... unless you are making beer in which case 129 might be a bit more accurate (tho brewing is not my area of expertise).

There’s lots of BBB ("blah, blah, blah") online on how to calculate alcohol ... all pretty good for insomnia - viz. http://www.realbeer.com/spencer/attenuation.html .

Factoring out the sugar addition from backsweetening; assuming you arrested fermentation prior to backsweetening (continued fermentation obviously changes things), should not be too tough ... it would just be some simple arithmetic.
You would have to have taken gravity readings just before and just after you backsweetened so you would know the amount of apparent gravity to disregard.

which I did not do, so I guess I am guessing at this point? When everything is said and done is there no easy way to determine alcohol content. Last year during my Otobrewfest party some one got the bright idea to add vodka to the cider....I am afraid that at 9% or higher if they decided to do that again it could be a long...or short night for some folks