Measureing ABV without OG

I made 9.5 gallons (supposed to be 11, but I messed up) of centennial blonde ale on Sunday. Due to numerous problems, I was pretty frazzled when I got everything into fermenters, and I forgot to measure the original gravity. Is there any way to measure the ABV of a beer without the OG?

It doesn't really matter at this point, since I can't do anything about it, I just like to know.

I think White Labs has a service where they will do it for a charge. I've not used it and cannot recommend one way or the other.

You need a whole bunch of laboratory equipment to test without an OG. Knowing your OG and FG allows you to calculate it close enough.

At this point it is just a WAG or a SWAG.

You can assume that your brew software will predict a pretty close OG. If you know what efficiency you get it is usually pretty close. I know that I am usually within a couple of points of my predicted OG because I have set my efficiency to what I usually get.

beergolf said:

At this point it is just a WAG or a SWAG.

You can assume that your brew software will predict a pretty close OG. If you know what efficiency you get it is usually pretty close. I know that I am usually within a couple of points of my predicted OG because I have set my efficiency to what I usually get.

Click to expand...

I changed a number of things (new MLT, brewed inside instead of out, different thermometer), so I do not feel like I can accurately guess my efficiency.

White Labs charges $138 to test the ABV, along with some other things, which is not in my price range. Looks like I'll have to treat the ABV as a surprise!

Then it definitely is a WAG, but guess what? You made beer....

You need to do a test after they are ready. Drink several and judge your sobriety?.......

I have forgotten to take OG's before myself. I don't brew overly high alcohol beers anyways. So I can safely guess my beers are always between 4.5% to 6%.

Gary

Someone posted a thread here on exactly how to do this. I tried searching for it but I couldn't guess the right keywords.

It was a bit technical for my knowledge but basically he said you take a specific gravity reading. You the then boil it some and then top it back up with water to the original volume. and measure the specific gravity of that. He said *viola* that's your o.g. although I think he meant the difference between the two can determine your o.g.

*My* take is: If you boil you remove the alcohol but keep your sugars. Hence if you compare the two potential alcohol reading the difference should be your current actual alcohol. ..... shouldn't it?.....

And then if you still want the O.G. (why? you have the ABV, so....) You can take the difference and add them to you current specific gravity (well, I don't know if the gravity readings are linear but you could add your ABV to you potential alcohol to get your original potential alcohol and figure your o.g. is the gravity that corresponds to that.)


Now, can somebody who actually knows his ass from his elbow verify and expound on that? (or find the other thread)

Cant find that thread *anywhere*.

But here are instructions on how to use the boiling method for wine.