Author Topic: testing a hydrometer  (Read 448 times)

Offline case thrower

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testing a hydrometer
« on: April 08, 2019, 07:13:40 PM »
My hydrometer and I aren't getting along.  I've tested it in plain water at the calibration temperature but I would like to test it against a known level with sugars.  Understanding that I am math challenged (and for some reason it seems to get worse after every birthday), how much sugar would I need to add to a pint of water to get a solution of 1.040?  I'm sure this has been covered before but I appreciate the help.  Thanks.
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Offline a10t2

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Re: testing a hydrometer
« Reply #1 on: April 08, 2019, 09:06:27 PM »
how much sugar would I need to add to a pint of water to get a solution of 1.040?

That's 10°P, so 16 oz x 10% = 1.6 oz *per pint* - i.e. add water to 1.6 oz sucrose to make 16 fl oz total solution.
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Online Robert

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Re: testing a hydrometer
« Reply #2 on: April 08, 2019, 09:11:24 PM »
how much sugar would I need to add to a pint of water to get a solution of 1.040?

That's 10°P, so 16 oz x 10% = 1.6 oz *per pint* - i.e. add water to 1.6 oz sucrose to make 16 fl oz total solution.
1 US fl oz water doesn't weigh 1 US oz.  Silly US measures.  But the idea here is right. 1.040 sg is 10°P.  10°P means a solution is 10% sugar by weight.  So if you weigh both your sugar and water to make a solution you know to be 10% sugar by weight,  you'll have your 1.040 reference solution.
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Offline case thrower

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Re: testing a hydrometer
« Reply #3 on: April 08, 2019, 09:27:55 PM »
how much sugar would I need to add to a pint of water to get a solution of 1.040?

That's 10°P, so 16 oz x 10% = 1.6 oz *per pint* - i.e. add water to 1.6 oz sucrose to make 16 fl oz total solution.
how much sugar would I need to add to a pint of water to get a solution of 1.040?

That's 10°P, so 16 oz x 10% = 1.6 oz *per pint* - i.e. add water to 1.6 oz sucrose to make 16 fl oz total solution.
1 US fl oz water doesn't weigh 1 US oz.  Silly US measures.  But the idea here is right. 1.040 sg is 10°P.  10°P means a solution is 10% sugar by weight.  So if you weigh both your sugar and water to make a solution you know to be 10% sugar by weight,  you'll have your 1.040 reference solution.

Ah, gentlemen.  Thank you both so much.  You've made an old man's life a little easier! LOL!  Thanks again.
Dave C.

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Offline a10t2

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Re: testing a hydrometer
« Reply #4 on: April 08, 2019, 10:01:54 PM »
1 US fl oz water doesn't weigh 1 US oz.  Silly US measures.

I do kind of take it for granted that my ground water is pretty close to the magical 4°C... still, it should be within measurement error (1%).
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Online Robert

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Re: testing a hydrometer
« Reply #5 on: April 08, 2019, 10:41:24 PM »
1 US fl oz water doesn't weigh 1 US oz.  Silly US measures.

I do kind of take it for granted that my ground water is pretty close to the magical 4°C... still, it should be within measurement error (1%).
At the reference temperature of 3.98°C, 1 US fl oz water weighs 1.0433 oz avdp.  (1 Imperial fl oz water does weigh nearly 1 oz, as the two were originally tied together by definition.)   Thus one US gallon of water weighs 8.3456 lbs, not the intuitive 8 lbs; 1 US pint weighs 16.6921 ounces, not 16; the discrepancies are not insignificant.  Greater than 1%, ~4.33% actually.
« Last Edit: April 08, 2019, 10:47:00 PM by Robert »
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Offline BrewBama

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Re: testing a hydrometer
« Reply #6 on: April 08, 2019, 10:49:33 PM »
A pint’s a pound the world around.  :)


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Re: testing a hydrometer
« Reply #7 on: April 08, 2019, 10:55:47 PM »
A pint’s a pound the world around.  :)


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Except not by weight, or outside the US where a pint's 20 ounces...    Metric looks pretty good sometimes.  I tried to go metric with brewing and baking for a while, but ended up having to convert back and  forth for so many reasons, I decided we've got to accept the crazy system we've got.
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Offline a10t2

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Re: testing a hydrometer
« Reply #8 on: April 08, 2019, 11:07:14 PM »
I yield! Too young to understand this Imperial/American units nonsense. ;D
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Offline BrewBama

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Re: testing a hydrometer
« Reply #9 on: April 09, 2019, 12:39:56 AM »
A pint’s a pound the world around.  :)


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Except not by weight, or outside the US where a pint's 20 ounces...    Metric looks pretty good sometimes.  I tried to go metric with brewing and baking for a while, but ended up having to convert back and  forth for so many reasons, I decided we've got to accept the crazy system we've got.

Just messin. I use 20 fl oz pints myself. I plan 32 pints from a cornie keg.


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Online Robert

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Re: testing a hydrometer
« Reply #10 on: April 09, 2019, 01:00:19 AM »
Then to confuse it a little more,  there were the traditional UK bottle sizes, the "reputed pint" of 13 ounces and "reputed quart" of 26 ounces, nominally 1/12 and 1/6 of an Imperial gallon.   Except that would add up to 156 ounces in a gallon,  and an Imperial gallon is 160, so those reputed measures don't look very reputable. 
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Offline Big Monk

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Re: testing a hydrometer
« Reply #11 on: April 09, 2019, 11:46:50 AM »
A pint’s a pound the world around.  :)


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Except not by weight, or outside the US where a pint's 20 ounces...    Metric looks pretty good sometimes.  I tried to go metric with brewing and baking for a while, but ended up having to convert back and  forth for so many reasons, I decided we've got to accept the crazy system we've got.

I'm all metric in brewing except for color. It's much easier.
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Offline Visor

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Re: testing a hydrometer
« Reply #12 on: April 09, 2019, 02:33:59 PM »
 Depending on your source, one gallon of a solution containing 1# of sugar, either cane or corn, will have an SG of 1.046 or 1.047. Assuming it's 46 and 40 is 86.9565217% of 46, and a pint is 1/8 of a gallon, 1.739 oz of sugar and water to make a gallon should be 1.040 SG. I'm sure someone will correct me if my math is wrong.
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Online Robert

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Re: testing a hydrometer
« Reply #13 on: April 09, 2019, 03:07:19 PM »
Depending on your source, one gallon of a solution containing 1# of sugar, either cane or corn, will have an SG of 1.046 or 1.047. Assuming it's 46 and 40 is 86.9565217% of 46, and a pint is 1/8 of a gallon, 1.739 oz of sugar and water to make a gallon should be 1.040 SG. I'm sure someone will correct me if my math is wrong.

I think you said gallon when you meant pint?  I get 1.7311 oz in a pint (US of course!) by your method.  At 68°F, that is. The exact figure for 1# in one US gallon at 68°F is 1.046214.  At any rate, since volume is finicky and temperature dependent,  weighing everything to get a 10% solution is still probably easiest.  Pick any units you like.  When we only know volume and want to use gravity to determine the weight of extract, that's one thing.  We can pick a simpler route when we're building in the other direction.
« Last Edit: April 09, 2019, 03:11:28 PM by Robert »
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Offline Richard

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Re: testing a hydrometer
« Reply #14 on: April 09, 2019, 03:54:20 PM »
A pint’s a pound the world around.  :)
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In the 1970s I worked with a Brit who had their version of this: "A pint of clear water weighs a pound and a quarter." It rhymed better when he said it. At that time they used Imperial pints, which are larger than our pints. So a pint is NOT a pound the world around because the definition of a pint is (or was) different.
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