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35657Re: Accurately measuring wash alc %

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  • Trid
    Jun 3, 2009
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      --- In new_distillers@yahoogroups.com, Nathan Stanley <catfish@...> wrote:
      > Hi all,
      > Today I did a brew and before I started I put my alcometer into the wash tub to see how much alcohol it had in it.

      OK, off the bat (and please correct me if I'm reading you wrong), but by "today I did a brew" do you mean you put together the ingredients (water, sugar, nutrients, yeast, etc.) and began the fermentation process?

      > The alcometer read lower than 0%, that is to say that it was floating so
      > high that didn't even show a reading. The alcometer is one of those
      > glass ones with a weight in the bottom and it floats in the liquid to give a reading.

      OK, here's the part where it gets more important that your terminology is dead accurate:
      If you're using an alcometer (which is designed to measure an alcohol water mixture; i.e. less dense than pure water) *and* my understanding of the first part is correct, then you're getting a reading exactly as you should expect.
      When you start off the fermentation phase of the process, you've added sugar and other ingredients to water. This mixture is more dense than water. The proper tool for measuring this is a "brewing hydrometer" which is designed to measure wort/must/wash (i.e. more dense than pure water).
      The term "specific gravity" which is used a lot in brewing, is the ratio of the density of a liquid to that of pure water. As such, pure water's specific gravity (or, as you see frequently abbreviated as "sg" or "s.g.") is 1.000. Denser liquids will have a specific gravity value of >1.0 and liquids less dense than water will have a s.g. value of <1.0
      Alcometers are calibrated in units of %abv to show how a mixture of water and alcohol (less dense than water) compares to pure water. The less dense, the more alcohol, and vice versa. Obviously pure water would read 0% Now, a wash that's just starting will be denser than water due to the sugars and other ingredients. If you put your alcometer in this mixture, it will read as if there is actually "negative" alcohol due to it not being able to sink down to the 0 mark.
      Brewing hydrometers are calibrated for denser liquids and account for any kind of mixture as they're just comparing density. Even so, the denser the liquid, the shallower it floats. To use one of these to get alcohol, you can't take a direct reading and have it tell you. You have to read the wash as you start the brew; called "original gravity" or "og" for short. Then, when you're done with the brew (this is where having to have patience comes in) you take another density reading to get your "final gravity" or "fg." The *difference* between the og and fg is what translates into your alcohol content of the brew.
      Once you run this brew through your still, then you have a pure(ish) mixture of alcohol and water, and that's when it's appropriate to use the alcometer for a measurement.

      > Why does it not show a reading when I do this? The best reason I can
      > come up with is the temperature of the wash, but I've never tested that theory.

      It's been tested and documented for decades, nay, centuries...temperature does indeed affect your readings. It might not be a bad idea to read and reread http://homedistiller.org a few more times so you can catch up to a lot of the proven theories.

      > And I would figure if the wash is cooler than normal it should
      > give a higher reading shouldn't it? Not lower?

      Higher density...which means one of two things, greater potential alcohol in your wash (as measured by the brewing hydrometer) or less alcohol in your distilled spirit because higher density = less alcohol/more water. The trick is to remember when either device is applicable. They're not interchangeable.

      > Only other reason I can
      > think of is there may be excess sugar put into the wash and that affects the buoyancy of the meter?

      As noted above, yes, more sugar leads to a denser wash and therefore greater buoyancy. This is the fundamental principle that allows a hydrometer to work in the first place. Denser wash (due to more sugar) gives you a higher sg reading.

      -hopefully this clears a few things up rather than further confusing things
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