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SG increase from dextrose or other sugars

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#brewlife

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Pretty simple question but i cant seem to find an answer without converting from ppg to i dont even know what.

Anyone know a formula to calculate the SG increase you get from dextrose or other sugars in KG/L assuming dextrose has an extract potential of 1.046?
 

MHB

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You need to use Plato (oP) and a very simple equation. Naturally the amount of Sugar (or anything else) and the Volume its dissolved in are equally part of the equation.
Plato is W/W% solids in solution 100g of sugar in 900g of water is 10% Weight/Weight solids, given that 1L of water is about 1kg.
Couple of things that will help, Sucrose (white sugar) is 100% solids, Dextrose (Dexter rotated Glucose Monohydrate) has that 1 water molecule (mono = 1 Hydrate = water) works out to be 91% Solids and 9% water that wont add to your SG, LME and honey are about 80% solids and 20% water.
So 1kg of honey will only raise the SG 80% as much as would 1kg of sugar
There is a much more complicated equation relating SG and oP but across the brewing range (from say 1.000 to 1.070 there is a close approximation namely SG=(4*oP)/1000 +1.
Play around with the equation and 10% (10oP) wort has a SG of 1.040 from SG=(4*10)/1000+1
We need the mass of the wort from Volume X SG = Mass i.e. 23L of 1.040 wort will weigh 23*1.040=23.92kg as it is 10% solids we can say it contains 23.92*0.1=2.392kg of solids.

Sorry just putting all the pieces into place, we can combine it all into one equation Mass in Solution=V*SG*oP
Depending on how good you are at rearranging equations (high school was in the 1970's) its easy enough to stick the equation is excel or another spreadsheet and then use Goal Seek to find the answer. (under the Data tab)

If you had 23L of 1.040 wort and added 1kg of Honey (0.8kg solids) what would the new SG be
Work out the mass of solids at 1.040 (2.392kg)
Add the extra mass (0.8kg) to give you the total mass in solution 2.392+0.8=3.192kg
You have added 1kg of honey (which is about 1L) so you now have 24.92kg with 3.192kg of solids.
3.192/24.92=0.128 or as a percent 12.8oP gives an SG of 1.051235... call it 1.051

A spread sheet lets you what if really easily or ask "how much LME to get to 1.060" type of question.
I think the PPG of Dextrose is less than 1.046 I think that for sucrose, DEX will be 9% lower, could be wrong don't use PPG (well Points, Pounds or Gallons) all that often.
Mark
 

#brewlife

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Mark,

Thanks for taking the time to explain this. Your contributions on this forum are always extremely valuable.

Not to detract from your extremely thorough answer, however if anyone else ever looks for this:

SG=(4x)/1000+1 therefore x=(SG-1)*1000/4

3.192/24.72=0.129 or as a percent 12.91oP gives an SG of 1.0516505... call it 1.052


Feels like primary school all over again.

Cheers
 

MHB

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I still get 24.92, not 24.72
23L X 1.040 = 23.92 plus the total mass added in example that's honey solids and water (1kg) total mass is 24.92 not 24.72. The 0.8 only adds to the total solids. Comes to 1.0512359 if you want to get picky.
Lots of ways to rearrange the equation some people would use x=(SG-1)*250, I just find the 4 so easy even I (a finger counter) can usually get the right answer in my head.

Mark
 

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