What ABV cider did I make ? By refractomer 7%, by weight of released CO2 estimate 11%

[azaxev]

Hello,

Bought 3L unpasterized cider with advertised 92g/L of sugar, measured 10.6Bx (=111g/L, sg=1.043). Added 270g sugar for 10% alcohol potential, mixed in 1tsp EC-1118 activated at 36'C.

Good shake, refractomer measured 17.94Bx/1.074SG, total weight 3598g including 66g 4L plastic jug.

Hooch was sitting for 11 days under my desk, at around 18-22'C.

Today, refractomer measured 6Bx/1.0237SG. Brewer's Friend estimates ABV=6.6% standard method or 7% alternate method.

Current weight 3324g, loss 274g of CO2 -> converted sugar 560g, created 286g ethanol. ABW=286g/(3324g-66g)=8.8% and ABV=ABW/0.8=11%

Still very new to this. Placed it outside to cold crash, so hopefully can rack it for holidays next week. Curious, what exactly did I make. Refractomer seems convenient and works well for sugar+water combination as refractive index of that compound is well researched and documented, I am not convinced it works well for sugar+water+ethanol combination (see Colin McFaul explanation here)

Thanks for responses

 

[dmtaylor]

None of the above. The closest you're going to get probably is with Sean Terrill's calculator but you need to change his default correction factor from 1.04 to something else, likely closer to 1.00. If you really NEED to know SG or ABV, you're going to have to actually measure using a real hydrometer. Otherwise, my best guess looks like:

 

[hotbeer]

Original weight - Current weight includes more things lost than just CO2. IE. water vapor. CO2 gas holds water vapor so if CO2 blows off, then so is water.

 

[dmtaylor]

Original weight - Current weight includes more things lost than just CO2. IE. water vapor. CO2 gas holds water vapor so if CO2 blows off, then so is water.

True. AND ethanol too.

 

[Zambezi Special]

Today, refractomer measured 6Bx/1.0237SG. Brewer's Friend estimates ABV=6.6% standard method or 7% alternate method.

This is wrong.
Common mistake, but refractometer readings need to be corrected in the presence of alcohol.
You need to use another calculater: Refractometer Calculator - Brewer's Friend

 

[azaxev]

Thanks all, so for refractometer there are different calculators than for hydrometer. That makes more sense.

For the accuracy, using 1.0 correction, Sean Terill calculator (thanks @dmtaylor) gives 8.9% and Brewer's Friends calculator (thanks @Zambezi Special) gives 10.15%, => that is 14% spread between the two.

So we can say my cider is between 8.9 - 10.15% ABV.

My OP weight loss based estimate 11% is not that far from the calculator, only 8.4% error from higher value, that's less than two calculator spread. Water and ethanol evaporation seem like not huge factor. For example: fully saturated air with RH=100% at room temp 20'C carries only 17g of water per 1.29kg of air, = 1.3% air weight. There are different evaporation conditions in pressurized CO2 air, but I think the weight method may still be useful, only factor weight by 90% to account for evaporation and should be in ballpark with empirical calculators.