balgiere
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I always have a hard time reading my Hydrometer. My question, is there a reason why weighing a sample of beer would not give you the same reading as a Hydrometer?
Hydrometer vs Weighing a Sample
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It's possible but I think you would either need to take large volume samples or get a very high resolution scale to get very much resolution out of your weighed sample.
For example: the weight of two of samples of beer, both 175 ml, one 1.050 specific gravity and the other at 1.010 specific gravity, the difference in weight is only 6.99 grams.
My scale is only good to +- a gram, that would mean that taking weighed gravity readings of 175 ml samples could only be accurate to within +- 6 points.
(And that doesn't take into account how accurate your volume reading of the sample is)
For example: the weight of two of samples of beer, both 175 ml, one 1.050 specific gravity and the other at 1.010 specific gravity, the difference in weight is only 6.99 grams.
My scale is only good to +- a gram, that would mean that taking weighed gravity readings of 175 ml samples could only be accurate to within +- 6 points.
(And that doesn't take into account how accurate your volume reading of the sample is)
In theory it could be done with incredibly high accuracy. But you need incredibly accurate measurements to be able to do it, as very small volumetric or weight errors can have a drastic effect on the numbers unless (as indicated above) you're working on a very large scale, which is very difficult to do with household equipment.
It would require the ability to know the volume of the wort exactly.
Let's put it this way, even with trouble reading your hydrometer, the margin for error and still get close is far, far higher than if going by weight.
brick_haus
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Unless you can accurately measure volume (a pycnometer may work?), precisely control temperature and have an analytical balance with a resolution of .001g, you should stick to the hydrometer method.
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The weight would be no problem, my cheep digital scale is accurate to .01 gram. The volume would be the challenge. Stick to a hydrometer, what's so hard to read? If you can't see, take a picture and zoom in.
Get a bottling hydrometer. They have .001 graduations up to 1.040. Easier to read.
This too. The only hydrometer I use is 0.990-1.020. Easy as pie to read.
brick_haus
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Never even thought of that, going shopping for a narrow scale hydrometer... Great advice.
A pycnometer does work and the beauty of it is that you do not need to measure volume accurately. What you must do, however, is fill it to the exact same volume, whatever that may be. Fortunately, temperature control is not necessary in at least one design
http://www.capitolscientific.com/Ki...vity-Bottles-with-Mercury-Thermometer-Seriali
With it one fills the bottle with cool liquid and watches the thermometer as it warms and, due to expansion, exits the side arm. When 20 °C is reached (or whatever temperature you want the SG at) you cap, rinse away any beer on the outside, dry and weigh. The specific gravity is the ratio of the tared weight of the pycnometer with sample to the tared weight with DI water.
Clearly accurate weighings are neceessary. If you want to read SG accurate to 0.0001 you would need a scale that measures to accuracy better than 0.0001 times the weight of the pycnometer plus beer. A 50 mL pycnometer might weigh 75 grams and so the balance would have to read to better than 0.0075 grams or 7.5 mg. This is not terribly demanding but not typical of the kitchen scales we use to weigh our hops either. To read to 0.001 SG would require the ability to measure 75 grams to better than 75 mg.
It's much simpler with a hydrometer.
Narrow range hydrometer FTW
(measure at the correct temperature for your hydrometer. Written on same )
Calibration temperatures.
brick_haus
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Ahhh, ASTM D153, I wasn't aware of this standard, All of my experience has been ASTM D70, semi solid bituminous material...Different protocol entirely.
Actually in our case it is ASBC MOA Beer 2A, now archived as no one does it this way any more but if you really want to know about your beer and have a few bits of distillation gear and a good balance you can get beer (or wort) SG, OE, TE, AE, ADF, RDF and ABV with a pycnometer. It requires taring the pycnometer and then getting weighings on DI water, the beer, the distillate and the distillation residue. The tare weighing is trivial but the other four, especially the beer which must, obviously, be completely degassed, aren't. It's an afternoon in the lab for sure (for one beer).
BeardedBrews
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I have trouble reading a hydrometer (old eyes), plus I don't like taking a large sample. I have a refractometer and it is great for OG, but I always doubt the calculated FG.
I bought a pycnometer to try this out. I got some 25ml ones with out the thermometer. I just made sure everything was at the same temp when I made my measurements.
I made a random sugar water solution and the pyncnometer said my SG was 1.028. I then checked it with my refractometer and it was 1.028. It looked close to 1.028 with my hydrometer, but like I said, It is hard for me to read.
I also checked it with an Irish Red Ale that was ready to be kegged today. The pycnometer said, 1.013, the hydrometer said 1.014 ish, and it was 8 brix on the refractometer. With a an OG of 1.060 the calculated FG from the refractometer is 1.015
I am liking the pycnometer method the best for determining FG.
Other than all the work, they are great.
I don't see how it is more work after you initially weigh the pycnometer when full and empty. After that you pull a sample and weigh it. I guess the extra 30 seconds to weigh the bottle and do a calculation is more work but I would spend as much time, if not more, trying to read the hydrometer or doing the calculations when using a refractometer.
The usual reason for use of a pycnometer is that you want answers more accurate than a hydrometer gives and it is usually done as part of a sequence of tests in which AE, TE, and ABV are determined. This involves weighings for tare, distilled water, beer, beer residue after distillation and beer distillate. The pycnometer must be scrupulously clean before the tare weighing and thoroughly rinsed with whatever the current sample is to make sure there is nothing from the previous weighing to contaminate the current one. Attemperation to exactly the right temperature is required.
If all you want is the SG of a beer or wort sample to accuracy comparable a cheap hydrometer then a pycnometer is overkill. Just put a weigh boat on the scale, tare it, pipet 1 mL of the beer into it and read the scale. Divide by the density of water at the reference temperature.
If all you want is the SG of a beer or wort sample to accuracy comparable a cheap hydrometer then a pycnometer is overkill. Just put a weigh boat on the scale, tare it, pipet 1 mL of the beer into it and read the scale. Divide by the density of water at the reference temperature.
brick_haus
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All of that is true AJ, but for the purpose that Loredo has in mind (getting close), the entire protocol may not be necessary. I Would however recommend that the temp of the wort/beer, the reference standard (distilled water)nand the pycnometer be very close. Calibration of the pycnometer prior to every test may be superfluous.
I favour weighing primarily because it involves lesser quantities and arguably less mess. Aside from an sg bottle, there are micropipettes (say a larger one that takes up to 5000 microlitres). Sure, they have their inaccuracies (typically calibrated and certified to 1-1.5%), but a good protocol could negate that: we are not really interested in absolute density but relative density to pure water, and both at the same temperature (not necessarily at standard temperature either, for our purposes at least, since the differences in coefficients of expansion are negligible for our purposes).
I use a 5000 microlitres one calibrated at 2500 (mean volume is 2501.5) and I take three samples or more of 4x2500 (10ml per sample) and have three readings of distilled water at the same equilibrium temperature. Divide sum of sample weights by sum of water weights for sg.
I use a 5000 microlitres one calibrated at 2500 (mean volume is 2501.5) and I take three samples or more of 4x2500 (10ml per sample) and have three readings of distilled water at the same equilibrium temperature. Divide sum of sample weights by sum of water weights for sg.
You can buy a 100ml calibrated, glass picnometer for about $20 on Amazon that will enable you to make very accurate gravity readings, provided you have an accurate gram scale to weigh it on. The device can also allow you to check the accuracy of your hydrometer, if you wish.
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Agree. I used the same for ages with everything density related, but always found it a bit messy with ejected excess fluids on and by the bottle, and cleaning up the bottle after (esp with multiple sampling). Once I experienced micropipettes, that has been my preferred method. Volumes are also much less. For both, I still need a reference sample of distilled water (to avoid temperature control) and a microgram balance. I rinse tips with a beaker of sacrificial sample as well as distilled water. I only use the sg bottles for periodic recalibration of metering pipettes nowadays and only water goes into them (lazy washer).
