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18

The general principle is based on density. That is, less dense things will float on top of denser things. By analogy, imagine a human floating in a pool of water. Now imagine a human floating in a pool of saltwater- the human will float higher in the saltwater, since the density of the saltwater is higher. A hydrometer works similarly- it's just a ...


17

If brewing all-grain, taking gravity readings after mashing allows you to calculate your mash efficiency. If your efficiency is low (meaning you're not getting good conversion), you can use this knowledge to pin down problems in your recipe, milling, and mash/sparge processes. Measuring the gravity before and after fermentation allows you to calculate the ...


11

This is a community wiki post. Anyone with more than 100 reputation may improve it. I get no reputation points for votes. Background Definition Specific gravity (SG) is a measure of density. By convention, pure water has a SG of 1.000. Substances denser than water have a higher specific gravity. For example, if a beer has an OG of 1.050, it is 5% heavier ...


10

If you boil the entire volume of your extract batches, go ahead and measure it. But most extract brewers do a partial boil and add top up water afterward. In that case, it's REALLY REALLY REALLY hard to get the extract and water mixed thoroughly enough to get an accurate reading. The extract is heavier due to the sugar in it and sinks to the bottom of the ...


8

Good Answer by Fishtoaster. The science is ancient, discovered by Archimedes. 1: Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object. In other words, if you put a ball, with volume 1 litre completely under water, there is an upwards force on the ball (buoyancy or flotation) ...


7

I'd bet that you didn't get it as well mixed as you think you did and you got a false reading. I've seen it happen many, many times. The other thing to address is your boiloff amount. You should be boiling off maybe 1.5 gal. in an hour. Boiling off 50% of your wort needs to be addressed.


7

Pure sugar is the most fermentable substance, at 1.046 points per pound per gallon. With 12 pounds of sugar in 3 gallons, you'd expect a OG of 1.183. Honey has an estimated yield of 35 ppg, and correspondingly the gravity would be lower - 1.135. There could be 3 possibilities for the observed high gravity the stratification is causing the reading to be ...


7

Here's some tips on getting an accurate hydrometer reading: check the hydrometer is calibrated, by checking that water reads 1.000 at the calibration temperature (either typically 65F or 20C). I've tried both distilled water and tap water and by both read the same. when taking a sample from a extract-based brew, particularly partial boil where top up water ...


6

If we steal the numbers from this question, we can assume that liquid malt extract has a value of about 37 points per pound per gallon, and dry has about 44. This is not exact. total gravity points needed = Desired total gravity - current total gravity total gravity points needed = 47 * 5 (desired reading * desired volume) - 37 * 5 (current reading * ...


6

A number that big strictly sounds like mixing errors to me. Stratification of warm wort and cold top off water happens a lot. You need to shake vigorously anyway to get some aeration into the fermentor. Take your gravity readings after that step in the future. Also, if you used 2.5 gallon of water for the boil and 3 gallons to top off, what happened to ...


6

Two most prevalent issues for poor efficiency when batch sparging are 1) grain crush and 2) void volume in the tun. 1) Take a real close look at your crush. Crush it twice if necessary. If you are getting your grain pre crushed through a mail order, I'd invest in a mill and start doing it at home. My LHBS has a mill that is fixed to a certain gap. ...


6

You are absolutely correct. Unless something is dissolved into the liquid, or there's so much trub that the hydrometer is sitting on top of it, the reading will be unaffected.


5

I have brewed many batches where I never checked the gravity in the past. You don't really need to check the gravities to make great beer. You do run the risk of not knowing when a beer is complete and maybe having overcarbonation issues in the bottle. But good fermentation practices should, normally, take care of that. However, I think that when you get ...


5

Measuring the OG post boil isn't the right place because if its off, how do you fix it? You'll have to calculate how much you are off and what amount of DME to add, all the while the wort is sitting hot, but cooling. The hop profile will be changing slightly as it sits hot. If you add the DME at this point you'd have to stir it to get the DME well mixed, ...


5

Could be many things. The first thing I would do is separate your conversion efficiency from your lautering efficiency. That will narrow down the problem. The article at this link has some really great information on efficiency. It gets a little technical, but the chart in the Conversion Efficiency section is especially interesting. What it's saying ...


5

(TOG - GR * (BV/FV)) / (45/FV) = lbs of DME to add pre-boil to hit target OG TOG = Target Original Gravity in Points GR = Gravity Reading in Points BV = Boil Volume (This is what you are taking your reading from) FV = Final Volume (i.e. 5 gallons) 45 = # Gravity Points you get per lb of DME per gallon So lets say you are making a 5 gallon smash beer with ...


5

Yep, you've got it. I've seen it and had it happen many times before I started doing full boils. Even when you think you've got it well mixed, you probably haven't! Since you use extract, it's going to be more accurate to calculate the OG than measure it.


5

An OG reading of 1.12 seems about double what you would expect for that grain bill, and gravity is only really affected by dissolved solids. Obviously the first thing you should do is check your hydrometer to make sure it is accurate, that is almost certainly the cause of the error. In water the specific gravity should read 1.00 since specific gravity is ...


5

You do it by multiplying the ratios of the imperial/English units to metric units: 1 kg is 2.204 lb 10l is 2.641 gal To convert from pounds per gallon to kilos/decaliter you multiply by 2.204/2.641 = 0.834 The answer is then 46*0.834 = 38.4 points per kilo/10 l. Edit: I always find these things confusing with "cascaded" ratios - points per pound ...


5

If the starter fully fermented, most of the 1.040 should be gone; normal yeast attenuation is around 75%, so you should have 1L of 1.010 beer in the starter vessel. 1L of 1.010 beer into 19L of 1.076 OG wort would reduce the OG down to about 1.073. (76 points * 19L + 10 points * 1L) / 20L = 72.7 points = 1.073. Though if possible, you should try to ...


5

If you follow a process like this, you won't be far off: Dilute the syrup to create a 10% solution. E.g. add 10g of syrup to 90g of water and stir well. Take the specific gravity of the 10% solution, e.g. 1.030 Express this as a fraction of a 10% solution of sucrose, which has specific gravity 1.040. So, our example of 1.030 is .75 the gravity of a 10% ...


4

Assuming you are using the hydrometer right: It could be your efficiency in the steep. If that is the case you are working at 64% efficiency instead of 72% like the recipe says. ( 70 GU * 0.72 efficiency / 78 GU = 64.6% ) Rinse the grain bag with hot water around 170ยบ. That will get more sugar out of the grain. How much wort did you get? If you ended ...


4

If you're doing a concentrated boil, it's possible you're just adding too much water to the fermenter when you finally put it together. For a five gallon batch, a difference of about half a gallon of water will cause that exact difference in OG. If you're doing a full wort boil, it could be the difference between boiling with the lid on and boiling with ...


4

A late malt addition doesn't affect final gravity. The only difference compared to a regular addition is that a 1 hour boil alters the flavor and color of the extract to a small degree. (The wort gravity will also be different for most of the boil, affecting hop utilization, but since the recipe states a late addition, this will have been taken into ...


4

EDIT: I'm not sure I realized it was 50 points we were talking about here, or just let my attention wander for a bit! Suspended solids can make a difference (see the comments), but you'd almost have to be measuring the SG of slurry for it to make that much of a difference! If the original recipe called for 2 cans of extract, and you used 3 then that's just ...


4

You don't need a starter since you're pitching to 1/4 batch size that a whitelabs vial is good for. Normally you'd use 2-4 vials for a 20 liter batch, depending upon gravity, so that's equivalent to 1/2 to 1 a vial for a 5 liter batch. For the detailed figures, see Always making a starter vs. following package description. One way to know the OG prior to ...


4

The key piece that's missing here is extraction efficiency - how much sugar you can get out of the grains. In the calculator, it's set at 80%, but it's doubtful you got that just from steeping and lautering in a pot. You typically need continual recirculation to get 80%+. With my old equipment (a large cooler with a hand-made series of pipes with slits.) I ...


3

The usual problem is that a brewer will do a partial boil and top up the fermenter with water. Since wort, containing sugar, is heavier than water it will sink to the bottom of the fermenter. When you take the sample, you're getting watered down wort from the top of the fermenter. When doing a partial boil, it's usually easier to compute the OG than to ...


3

Assuming you had the right amount of everything, I'm guessing your mash efficiency was off for some reason, so it's time to troubleshoot: 160 'F is fairly high for a mash temperature, generally you want something in the range of 150-155 'F. You may have denatured most of your beta amylase and lost efficiency here. How much water did you use in the mash? I ...


3

Sugar provides 46 gravity points per pound, per gallon (PPPG). Based on the nutritional data, you've got a total of 2.964 kg of sugar, which is 6.53 lb. Your total volume is 5 gallons + 3 cups = 5.1875 gallons. (6.53 * 46) / 5.1875 = 57.9 So your predicted starting gravity is 1.058



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