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Second question first, yes the volume listed for the dextrose on the design tab is an estimate of the volume displacement of that ingredient. Other than that, the program does not use this number to adjust the water volumes needed.
The program does not even take into account the thermal expansion of the water when calculating out the pre-boil gravity. The pre-boil gravity target BeerSmith calculates is off by the thermal expansion coefficient. If you have any significant volume added from your pre-boil addition, then that will compound the error in this target.
Thanks! This will explain my difference between measured and calculated SG. I used the software to build a wash for distillation 20% malted barley and 80% dextrose. The dextrose is added into the boiler.
I build an experimental recipe in BS3 in such a way that the preboil volume is 100l and adding 1kg of sugar (no other fermentables) into the boiler. BS3 estimates the preboil gravity is 1.024. This seems very high for 1 kg sugar in 100l
I then used another calculator to calculate the gravity of 1kg sugar in 100l water and it equates to 1.002.
What 'type' of recipe did you make? If your recipe type is set to all-grain, then the program uses the brew house efficiency to calculate how much of the fermentables (sugars included) make it to the fermenter. To get a result more in line with the calculator, change the recipe type to 'extract'. Then the program will use the points from the extract and the volume (fermenter + process losses) to calculate the gravity target.
At this stage I'm only looking at the figures stated in the pre-boil tab. To try and understand how BS3 work with sugar added to the kettle I did not add any fermentable to be mashed. So the post mash gravity is 1.000. I changed the batch size so that the pre-boil volume is 100l. I added 1kg of sugar to the kettle (boil). According to me this should not be different than taking any large container fill it with 100l of water and add 1kg of sugar.
I know BS3 does not take the volume displacement into account. Which in this case is almost 630ml.
What I do not understand is why does BS3 calculate the pre boil gravity to be 1.024