Determining ABV proof After back sweetening

[Otto Distilling]

I've been experimenting with adding spices and sugar to my rums. The problem I'm running into is that after I add the sugar (simple syrup or cane spirit caramel) the ABV reading on my alcohol hydrometer drops significantly. Obviously the small amount of water in the syrup would lower the ABV, and I've read that sugar lowers the ABV as well, but I don't think by the amount I'm reading on my hydrometer. My question is, how do you determine the correct ABV of the rum after back sweetening? What are the alternatives to using a hydrometer?

[stillwagon]

You will have to proof by distillation, or have it done by a ttb approved lab. I use Vinquiry.

[Otto Distilling]

Thanks Stillwagon. Have you used a digital alcohol meter before? If so is there one you recommend?

[Silk City Distillers]

For what purpose?

[Otto Distilling]

For measuring the ABV after adding sugar. But I've done more research and realized the digital meters don't account for sugar either. Found this thread in the ADI Forums and it basically summed up what I need to know.

http://adiforums.com/topic/9644-proofing-spirits-proofed-with-sugars/

My only remaining question.. Is there a ballpark figure for calculating the ABV accounting for the sugar added on a much smaller scale? Ex if I were to add 2 oz simple syrup (38g sugar) to one .75ML bottle of 40ABV, how much would the ABV decrease? 

[JailBreak]

1 hour ago, The Don said:

For measuring the ABV after adding sugar. But I've done more research and realized the digital meters don't account for sugar either. Found this thread in the ADI Forums and it basically summed up what I need to know.

http://adiforums.com/topic/9644-proofing-spirits-proofed-with-sugars/

My only remaining question.. Is there a ballpark figure for calculating the ABV accounting for the sugar added on a much smaller scale? Ex if I were to add 2 oz simple syrup (38g sugar) to one .75ML bottle of 40ABV, how much would the ABV decrease? 

For my added sugar spirits I do a ballpark calculation using simple math. 750 ml of 40% ABV translates to 300 ml of absolute alcohol (750 * .4). Adding 2 oz (59.15 ml) of simple syrup to the 750 ml gives you an approximate net of 809.15 (I'm sure there's some reactions that cause this to be more or less to a degree). Now we just divide 300 by 809.15 to get an answer of .371 or 37.1 ABV. Like others have said, you're still required to do a gauging by distillation but this should give you a rough idea. There's also a program that people rave about called AlcoDens. It could also be something to look into.

Edit: The above is more for recipe development. It won't tell you how much the proof is obscured during a hydrometer gauge. 

[daveflintstone]

My goodness gracious just use alcodens lq...

[indyspirits]

4 hours ago, daveflintstone said:

My goodness gracious just use alcodens lq

Absolutely the best money I have ever spent. 

[Otto Distilling]

Thank you all for the help!