Mead-making and measuring alcohol content

January 10, 2007 6:20 AM

Measuring alcohol content without a hydrometer?

So I am making a couple batches of mead. Unfortunately, this is the first time I've done this, and I forgot to measure the specific gravity before charging with the yeast starter.

Bubbling is slowing down, and I'm a few days away from transferring to the secondary vessel. I'm curious what the rough alcohol content will be in the final product.

Without having a starting specific gravity, I don't think I can use a hydrometer to make the relative calculation needed for an accurate measurement. I'm assuming I can't use 1.0 as the initial specific gravity because of the (alcohol-like) sugars and other compounds in the starting broth.

Is there a way, without employing the services of the local organic chem lab, to easily measure alcohol content of a generic substance?

posted by Blazecock Pileon to science & nature (8 comments total)

How about taking proportional, yet much smaller, amounts of the ingredients, mixing them up, and measuring the specific gravity of that? Would this introduce too much error for your needs?
posted by Roger Dodger at 6:42 AM on January 10, 2007

Did you follow a recipe? You could scale the ingredients back to half a pint or so, and so measure the specific gravity of a near-identical liquid.
posted by Leon at 6:43 AM on January 10, 2007

When I've made beer, there's always been a "your specific gravity will be x-X at this stage" estimate in the recipe. Do you have something like that? If you get a hydrometer and measure specific gravity at the end, you should at least be able to calculate the alcohol content range, which should be fairly narrow.
posted by croutonsupafreak at 6:46 AM on January 10, 2007

We "roughly" followed two recipes. We added a little more of the herb flavorings, based on the recommendations of the recipe writers. I don't know if we can recreate the initial conditions precisely, and whether that imprecision would affect hydrometer readings too much.
posted by Blazecock Pileon at 6:51 AM on January 10, 2007

one thing you might try is take a sample of the brew, weigh it, heat it up to about 80c, which is just over the boiling point of ethanol. the alcohol should come out (and a small bit of water, too, though not as much). then weigh and measure the volume afterwards. if you assume that what's left the mixture is only alcohol, i think you can figure it out that way.

(this assumption might be poor though, someone could take a crack at figuring out how much water evaporates as well.)
posted by sergeant sandwich at 6:56 AM on January 10, 2007

Do know the weight of the honey you used? IIRC, a pound of honey in a US gallon of water will give you 1.036 OG. With some mathematical fumbling, you could likely figure out an approximate starting gravity.
posted by glip at 7:50 AM on January 10, 2007

If you have access to a refractometer, you can take both the refractometer reading and the hydrometer reading and use it to compute percent alcohol. One catch - I don't know the calculation, but you can plug the numbers into Promash. See this link.

Perhaps with a bit of googling, you can figure out the formula, if you don't have Promash.
posted by jclovebrew at 10:21 AM on January 10, 2007

Ah, I found an online calculator that can give you the starting gravity based on the ending hydrometer and refractometer reading. So from there, just do the regular calculation to get get % alcohol.

Enjoy the mead!
posted by jclovebrew at 10:25 AM on January 10, 2007