Pre-boil gravity adjustment

What went wrong? Was this supposed to happen? Should I throw it out? What do I do now?

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Pre-boil gravity adjustment

Postby Crusty » Fri Mar 05, 2010 6:14 am

Hi fellow brewers,
I have recently merged from Beersmith brewing software to Beer Tools Pro & need some help. I am brewing an all grain Amber Ale tomorrow & cannot work out how to use a dilution tool in BTP if there is one. I need to collect a kettle volume of approx 34 litres at 1.033sg. If I collect the required volume of 34 litres, but have a sg reading of say 1.035, how do I use the software to tell me how much water to add to the kettle to hit my target sg of 1.033?
Beersmith has a dilution tool that you add your volume & your sg & you add the required volume of water to hit target pre-boil.
Thanks guys,
Brian
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dilution

Postby slothrob » Fri Mar 05, 2010 7:49 am

With the Style tab selected in the bottom half of the window, you'll see the OG displayed. If this isn't your actual OG, change the Efficiency or Evaporation/hour, as appropriate. If this OG is higher than you would wish, change the Water Volume Added value, in the top half of the window, to get the OG you want, and to find out how much water to add.
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Postby Crusty » Fri Mar 05, 2010 9:06 am

Thanks for your input Rob,
I still cant make any sense of it. I went into Beersmith & typed in a pre-boil volume of 32 litres at 1.035 as an example. My target pre-boil is 32 litres at 1.033. Beersmith tells me to add 1.7 litres of water to the kettle giving me 33.7 litres for the boil at my target of 1.033. I tried changing efficiency, added water volumes in BTP & couldnt get anywhere. Bit of a noob.
Brian
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volume

Postby slothrob » Fri Mar 05, 2010 10:31 am

Make sure your Final Volume reads 32 liters, then increase your efficiency until your OG displayed reads 1.035. Now, adjust the volume in the Water Volume Added field until your OG reads 1.033.

Unless I'm missing something, I think the correct volume is actually 1.9 liters:
Based on the knowledge that:
volume x gravity (pre-diluton) = volume x gravity (post dilution).

32 L (actual) x 35 points (actual) / 33 points (target) = 33.9 L (target).
33.9 L (target) - 32 L (actual) = 1.9 L (to add)

As an aside, you probably have your reasons for wanting to make this adjustment, but I rarely make any post boil corrections to my all grain batches. I suppose I would if I was way off the mark, but I think the difference between 1.033 and 1.035 is really undetectable. Most craft breweries would also accept this as batch-to batch variability.
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Postby Crusty » Fri Mar 05, 2010 5:52 pm

Thanks again Rob,
I will have a go at that.
With your above calculations, does a points chart work like this,
1.049 = 49 points
1.045 = 45 points
1.036 = 36 points & so on.
Brian

Brewed an all grain Amber Ale this afternoon using Beer Tools, 23litre batch, 70% efficiency & had a strange pre-boil reading. Mahed in 16l at desired strike temp 73 , mash rested at 66.8, lost not even 1 deg after 60min rest. Collected first runnings. Sparged with 10.5l water at 76, collected runnings 10mins or so after a short stir & rest. Sparge round 2 with exact same measurement & volume as first sparge. Stopped collecting after desired 32 litres. Measured pr-boil gravity temp corrected, came in at 1.056 instead of 1.033, what the heck! In a slight panic, re-checked all measurements & volumes & all correct. I obviously achieved a greater than 70% efficiency. I actually had to add 7 litres to my pre-boil to achieve desired 1.033. After boil & cooled into fermenter, it is at 1.046, my target sg. I had to resort back to Beersmith dilution tool to work out water to add to pre-boil. Cant get it worked out in Beer Tools.
Brian
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Joined: Fri Mar 05, 2010 6:05 am
Location: Yamba, NSW, Australia


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