09 July 2014

My Hydrometer Broke! What Now?

OK! Time for a break from the science heavy stuff. Want a quick tip/technique? Try this on for size.

This for those of you who run into a broken hydrometer and find yourself unable to take an original gravity reading for your beer, wine, or mead.
First things first, always have a spare hydrometer. I've got 2 normal hydrometers and 3 fine scale hydrometers, and if any break I have a replacement that covers a similar range and immediately get a replacement. However, if you are not prepared for some reason, this process works perfectly (in fact it's how brewers used to measure their gravities, though they used pounds and barrels for their measures), and if you have very accurate scales and beakers it can actually be more precise than a standard hydrometer.

Things you'll need:
A scale that is precise to a minimum of 4 significant figures (look it up if you don't know what that means, it's important)
A way to measure a given volume (either 100 or 1000mL works best) such as a beaker or a flask
A way to take samples (a wine thief is essential to have period! (I meant exclamation point.))

Make sure that your volume beaker/flask can fit on the scale, and make sure your scale can measure the volume your using (for 1000mL you need a max of 1.3kg or more; for 100mL it needs to be able to weigh at least 130g).
Note: It is far easier to use SI units unless you feel like converting.

Here's the procedure for a 100mL sample:
1. Weigh your beaker/flask dry
2. Take a 100mL sample and put it into your beaker/flask
3. Weigh the filled beaker/flask
4. Subtract your beaker/flask weight from the reading
5. Transpose your decimal point so your number reads 1.XXX(X)
Ta Da!

Why it works?
100mL of distilled water at 4*C (at standard atmospheric pressure) weighs 100g. A hydrometer works by comparing this known density to the density of the unknown sample, usually correcting to 20*C (68*F). To do this adjustment by hand, multiply your result by 1.00177. If the temperature of your sample is not 20*C (68*F), then take the number after multiplying and plug it into an SG temp correction calculator.

Volume: 100mL
Beaker weight: 200.00
Sample temp: 70*F
Weight of total sample: 311.00g
311.00 - 200.00 = 111.00
1.1100 x 1.00177 = 1.1120 (rounded)
Temp corrected and rounded for SG 1.111

Note that this procedure will not work with fermenting must unless it has been fully removed of CO2, which requires some special equipment. However, if your in a rut and need to measure fermentation progress it will work, it just cannot be compared to a standard SG scale.

No comments:

Post a Comment