Specific Gravity - Who Checks it?

[Bob]

Bob, when it comes to extract I have to completely disagree with you here. 9.5 times out of 10 if you take your time and follow a set procedure of boil amounts, cooling, top off to the correct volume etc... and then give it 2-3 weeks in the primary and maybe some secondary time, your going to have exactly what the recipe called out. For extract brewers a hydrometer is still important, but its for that .5 times when you need to troubleshoot. If you don't have a good baseline of data you won't know what went wrong with that one batch, but that doesn't make the other 95+% of your beer mediocre.

Well...kinda. I submit that proper use of the instruments is part and parcel of "set procedure".

You are 100% correct that you need to have that "good baseline of data". How do you propose to do that without the instrument? Troubleshooting is impossible without data to analyze. If you don't, if you never use the instrument, what are you to do with that 0.5? Dump it? Dodge the exploding bottles?

There is no way to improve beer by taking a hydrometer reading after dumping in a bunch of sugar powder to say that you hit 100% efficiency and no hop alterations are required.

That's precisely what I said when I wrote, "A monkey could mix up a Cooper's kit and get bombed on the results". I suspect you're not mad enough to suggest that a tin of pre-hopped extract produces truly excellent beer.

Further, there is so a way to improve that sort of beer with a hydrometer - by tracking fermentation, by being able to spot the crappy yeast they leave in the lid of the tin pooping out at 50% attenuation. That has nothing to do with efficiency, everything to do with supervising your tiny workers.

There is however skill and patience in measuring out the proper amounts of ingredients and water and following the brewing process to a T every single time. That is what makes good extract beer, not taking 50 hydrometer samples.

Note I never said anything about hydrometer readings in a vacuum, outside of procedure. I maintain instrumental observations are part of a good extract-brewing procedure, part of the process.

Really, the hydrometer usage I've in mind transcends extract, all-grain or any other sort of brewing, because I'm not really talking about its use in the brewhouse; I'm talking about using the instrument to monitor fermentation.* I insist you cannot properly monitor fermentation without using a hydrometer to observe the metabolization of sugars to alcohols. I also maintain that arguing to the contrary is folly on a colossal scale; discrete data sets cannot be determined by looking at bubbles in an airlock! Or is there a unit of measurement of airlock bubbles which my Bamforth and Fix texts inadvertently omitted?

Cheers,

Bob

* I don't use a hydrometer in the brewhouse; I use a refractometer.

 

[reefwreak]

Very interesting thread. I've made about 7 or so batches now (all extract with steeping grains except the first 2, which were Mr. Beer) and never taken hydrometer readings. That being said, I bought a thief yesterday so on my future batches I'll be able to use a hydrometer. I have two questions to ask and since it sounds like many people around here have experience measuring specific gravity.

First question is:
I've tried to use a refractometer before (I've got one because my other hobby is Saltwater Aquariums, where I've always got to be on top of my tank's salinity), but I was unable to get a reading on it. I believe that a refractometer is a refractometer is a refractometer, the only differences were the scales listed on them. I know for alcohol they use specific gravity and degrees brix, however for aquariums we use specific gravity and ppt salinity. That being said, anyone who uses a refractometer, are there any tricks to using it with fermenting wort versus salt water? I just added drips, laid down the flap, and tried to get a reading like I would with saltwater (never had a problem with SW except if it isn't bright enough in the room to get a reading). When I looked through the eyepiece, it was solid brown, as if there wasn't enough light getting through, but using the same lighting I would have no problem with saltwater. Is the darkness and density of the beer that much of a problem that I'll need a brighter light to look at?

Second question:
Everyone is using a floating hydrometer (for the most part), but have you ever calibrated it? I know from aquariums that floating hydrometers are usually MUCH more accurate than the plastic swing-arm ones (which I've never heard mentioned around beer, probably for good reason), however even hydrometers can be off a few points, so it's best to calibrate them using a premade solution. Refractometers should definitely be calibrated to a specific gravity solution that you're sure of it's numbers (you can even hit a local aquarium store and see if they sell salinity calibration solution and then just compute the specific gravity into brix or whatever other method you would prefer it be in). Calibrating to a 0.000 fluid isn't a guaranteed calibration for measuring higher gravities.

If anyone wants some information on calibration, homemade calibration solution, and/or the instruments that can be used for salinity and/or density measurement, I suggest checking out our Reef Aquarium's magazine article on it written by a VERY smart phd chemist who participates in our community. Reef Aquarium Salinity: Homemade Calibration Standards by Randy Holmes-Farley - Reefkeeping.com

BTW I hope I don't upset anything/anyone with crossposting to another forum site. I don't know if that's allowed here or not, but it should be a far off enough topic to not upset anyone.

 

[Yooper]

If anyone wants some information on calibration, homemade calibration solution, and/or the instruments that can be used for salinity and/or density measurement, I suggest checking out our Reef Aquarium's magazine article on it written by a VERY smart phd chemist who participates in our community. Reef Aquarium Salinity: Homemade Calibration Standards by Randy Holmes-Farley - Reefkeeping.com

BTW I hope I don't upset anything/anyone with crossposting to another forum site. I don't know if that's allowed here or not, but it should be a far off enough topic to not upset anyone.

No, it's fine to crosspost to pertinent information- no worries.

I'm NOT an expert on refractometers (is Bob still around?) but I know that they are not accurate for fermenting/fermented wort, and many still use the hydrometer or complicated calculations after fermentation has begun.

A hydrometer can not really be calibrated- except if you float it in 60 degree distilled water, it should read 1.000. If it does not, you can simply +/- the difference. If if is far off 1.000, the hydrometer should not be trusted.

 

[Revvy]

Very interesting thread. I've made about 7 or so batches now (all extract with steeping grains except the first 2, which were Mr. Beer) and never taken hydrometer readings. That being said, I bought a thief yesterday so on my future batches I'll be able to use a hydrometer. I have two questions to ask and since it sounds like many people around here have experience measuring specific gravity.

First question is:
I've tried to use a refractometer before (I've got one because my other hobby is Saltwater Aquariums, where I've always got to be on top of my tank's salinity), but I was unable to get a reading on it. I believe that a refractometer is a refractometer is a refractometer, the only differences were the scales listed on them. I know for alcohol they use specific gravity and degrees brix, however for aquariums we use specific gravity and ppt salinity. That being said, anyone who uses a refractometer, are there any tricks to using it with fermenting wort versus salt water? I just added drips, laid down the flap, and tried to get a reading like I would with saltwater (never had a problem with SW except if it isn't bright enough in the room to get a reading). When I looked through the eyepiece, it was solid brown, as if there wasn't enough light getting through, but using the same lighting I would have no problem with saltwater. Is the darkness and density of the beer that much of a problem that I'll need a brighter light to look at?

Second question:
Everyone is using a floating hydrometer (for the most part), but have you ever calibrated it? I know from aquariums that floating hydrometers are usually MUCH more accurate than the plastic swing-arm ones (which I've never heard mentioned around beer, probably for good reason), however even hydrometers can be off a few points, so it's best to calibrate them using a premade solution. Refractometers should definitely be calibrated to a specific gravity solution that you're sure of it's numbers (you can even hit a local aquarium store and see if they sell salinity calibration solution and then just compute the specific gravity into brix or whatever other method you would prefer it be in). Calibrating to a 0.000 fluid isn't a guaranteed calibration for measuring higher gravities.

If anyone wants some information on calibration, homemade calibration solution, and/or the instruments that can be used for salinity and/or density measurement, I suggest checking out our Reef Aquarium's magazine article on it written by a VERY smart phd chemist who participates in our community. Reef Aquarium Salinity: Homemade Calibration Standards by Randy Holmes-Farley - Reefkeeping.com

BTW I hope I don't upset anything/anyone with crossposting to another forum site. I don't know if that's allowed here or not, but it should be a far off enough topic to not upset anyone.

Nah, we cross post stuff all the time...I thank you fro the link on calibrating the floating one...but may I suggest that you start a seperate thread about the refractometer. It's agreat question, and I know nothing about them, but you'll probably get some info/feelers if you post it in a new thread. More than likely the people who own refractometers have probably ignored this thread, or posted it an moved on...Maybe make the title something like aquarium vs homebrew refractometers, or how can I use my aquarium refractometer or something like that.

And thanks for the calibraton link...I haven't ever done it, and one one of mine it appears that the paper is unravelling inside a little bit on the bottom...so I've wanted to check it out or toss it, I have a couple more anyway.

 

[SkinnyShamrock]

Once before pitching, and once before bottling or moving to secondary to check if the fermentation is done. Always.

 

[FireBrewer]

1. Pre-boil with refractometer: helps prevent unpleasant surprises
2. OG with refractometer
3. FG with hydrometer: gotta test the sample for flaws (that's my excuse, anyway )

Always for me, unless I forget something. Watching my homebrew intake whilst brewing usually helps too.

 

[Bob]

I'm NOT an expert on refractometers (is Bob still around?) but I know that they are not accurate for fermenting/fermented wort, and many still use the hydrometer or complicated calculations after fermentation has begun.

Refractometers have no place in the fermenting room; it's easier to just suspend a hydrometer. As you say, it is possible to use a refractometer to measure the gravity of fermenting wort, but it's so bleedin' complicated you might as well use the hydrometer.

For that matter, refractometers should be used with care no matter where one uses them. Usually scaled in °Brix, they are designed to measure the percentage of sucrose in a pure solution. Wort has many different kinds of sugars. Thus, a correction must be made which varies from brewery to brewery. The refractometer user must calibrate his brewery to accurately use a refractometer. While it sounds complicated and scary, it really isn't: Take a sample of sweet wort. Take a refractometer reading. Chill the sample to safely measure with your hydrometer. [FONT=Verdana, Arial, Helvetica, Sans-Serif]Convert the hydrometer reading to Brix using the equation: Brix = (SG-1)/0.004. Then divide the reading of the refractometer by your actual hydrometer reading. You should have a number between 1.02 and 1.06. If you do this for several worts and average them, you will get a number that you can use for your brewery. My number is 1.04.[/FONT] [FONT=Verdana, Arial, Helvetica, Sans-Serif]Once you have this number, divide all of your subsequent refractometer readings by your calibration number to get the actual reading. For example, if your reading is 14.6 Brix then your corrected reading is 14.04 Brix (14.6/1.04=14.04). Then, we can convert the measurement in Brix to specific gravity. [/FONT]

A hydrometer can not really be calibrated- except if you float it in 60 degree distilled water, it should read 1.000. If it does not, you can simply +/- the difference. If if is far off 1.000, the hydrometer should not be trusted.

Yup. You can use a small screwdriver to calibrate a refractometer, but the only way to calibrate a hydrometer is to chuck it in the bin and purchase another. Really, there's no reason it should ever lose its calibration; it's not as though there are any adjustment points to bump - once you've bumped it, it's usually in a jillion pieces!

My hydrometer set is now more than ten years old (I have a set of three overlapping Brix instruments). They are remarkably accurate!

Bob

 

[jpsloan]

I always check my OG, directly before pitching. I do this to see how my wort is matching up to the intended recipe (which I generally reference by using Brewsmith).

However, and I'm sure someone will smack me for this... I don't check final gravity after fermentation. I have yet to attempt a recipe with a gravity over 1.055, and I leave my batch in the primary for a minimum of two weeks. Lately, three. I tend to go on faith that my typical session beers are fermented by the end of two weeks. And at this point in my brewing, I'm not worried about ABV. Should I get into trying to nail styles, or entering into competitions, I'll be checking final gravity at that point. Also... if I try a big beer, and need to know where the fermentation is precisely.

 

[jhb]

I check sometimes in the kettle (so I can make adjustments in case I have any efficiency surprises), always before pitching (so I can calculate efficiency and abv after the fact) and always at the end of primary (so I can be sure I'm done and also to calculate abv.)