Author Topic: weight/specific gravity/gravity points?  (Read 403 times)

Offline dzlater

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weight/specific gravity/gravity points?
« on: February 10, 2011, 11:20:36 AM »
First can someone tell me if I understand this correctly?
If 100 ml of a sugar syrup weighs 359.58 grams, it has a specific gravity of 3.59?
or do you subtract out the 100 gm of for the weight of the water and come out with 2.59?
Assuming that I have one of those right,
how would I figure how many gravity points it would add to a batch of beer?
 ???
Dan S. from NJ

Offline tschmidlin

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Re: weight/specific gravity/gravity points?
« Reply #1 on: February 10, 2011, 11:23:56 AM »
No, you've got it mixed up.  100 grams of sugar in enough water to make 1 liter total gives you a solution that is 10% sugar.  This corresponds to 10 brix, which is ~1.040.

To figure out how many points it will add, you can divide 40 by the total volume you're adding it to and that will be close enough.

<edit>Sorry, I misread your post.  100 ml of syrup that weighs 359 grams . . . that's really dense.  That's higher sugar content than honey, which should only be about 145 grams per 100 ml.  Are you sure you measured right?  That's more dense than sugar itself, with no water.

But to use honey as an example, 145 grams per 100 ml corresponds to a SG of 1.45.  So each unit of honey adds 450 points of gravity.  From there you take the final volume you'll have, the number of points you want, and calculate how much to add.  For example, if you're adding it to 19 liters and want to add 1 liter of honey, that's 450 points divided by the total volume, so 450/20 = 22.5 points added.

It's important that your volume units be equal, that's why we can just say 450 points.  If you want to add 100 mls of honey to 19 liters, that's 19.1 liters but the honey is in 100 ml increments, so divide it by how many 100 ml containers you could fill, which is 191.  450/191 = 2.35 points.

That might be a weird way of doing it, but it works.  Well, close enough anyway, you need to know the actual SG of the sugar solution and a couple of minor things come into play (like SG points is not exactly the same as 4 * brix) but like I said, close enough.
« Last Edit: February 10, 2011, 11:55:27 AM by tschmidlin »
Tom Schmidlin

Offline dzlater

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Re: weight/specific gravity/gravity points?
« Reply #2 on: February 10, 2011, 03:06:32 PM »
>>>>>>>>>>>>> Are you sure you measured right?  That's more dense than sugar itself, with no water.

>>>>>>>>>>>>>>>>>>>>>>
Ummm yea I measured it wrong I thought it didn't seem right I was in a hurry.
I think I got this:
100 ml weighs 134 grams
so that's 340 gravity points
if I have 300ml of syrup, and my batch size is 20.82 L (5.5 gallons)
that gives me a total volume of volume of 21.11
340 x .3= 102 gravity points
102/21.11=4.83 points add
or close enough for homebrew
« Last Edit: February 10, 2011, 03:08:15 PM by dzlater »
Dan S. from NJ

Offline tschmidlin

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Re: weight/specific gravity/gravity points?
« Reply #3 on: February 10, 2011, 11:53:53 PM »
>>>>>>>>>>>>> Are you sure you measured right?  That's more dense than sugar itself, with no water.

>>>>>>>>>>>>>>>>>>>>>>
Ummm yea I measured it wrong I thought it didn't seem right I was in a hurry.
I think I got this:
100 ml weighs 134 grams
so that's 340 gravity points
if I have 300ml of syrup, and my batch size is 20.82 L (5.5 gallons)
that gives me a total volume of volume of 21.11
340 x .3= 102 gravity points
102/21.11=4.83 points add
or close enough for homebrew

Yup, that's what I get too.
Tom Schmidlin