Author Topic: My actual pre-boil volume is more than estimated pre-boil volume (BIAB)  (Read 668 times)

Offline friis

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My actual pre-boil volume is considerably higher (about 0.4 gallons) than my estimated pre-boil volume.  This is around 165-170F during my mash out.

Unless I'm wrong, it seems like Beersmith already accounts for the heat expansion of the water when determining pre-boil volume.

After the mash I suspend my grains above my kettle and let them fully drain.  So maybe I get more water than others that just squeeze?

Any ideas?  Or where I can make adjustments to nail down pre-boil volume?








Offline friis

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Ah, I think I may know what is happening.  Would like someone to confirm if this is true or not.

Beersmith is telling me to add 8.95 gal of water at 157.6 F.  I added 8.95 gal of water at ambient/ground temp.  I should have 8.95 gal of water in my kettle at strike temp, or something in the neighborhood of starting with 8.68 gal of water at ambient temp (calculated by temporarily changing Cooling Shrinking from 4% to 0%).  Then due to heat expansion of the water, I end up with 8.95 gal at strike temp.

That would account for 0.3 gal of the 0.4 gal difference, where 0.4 was a bit of a guesstimate (but pretty close) anyways.

Is my understanding correct?




Offline Oginme

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Your interpretation is correct.  When BeerSmith calculates a volume it is at temperature stated.
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Offline Smellyglove

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I've mailed Brad a bit back and forth about this. And unless there is something in the conversation I misunderstood the only temp-correction BS does is from boiling down to pitch-temp. I've had a time where I was calculating thermal expansion left and right until I just didn't care about it anymore since there are other factors affecting the volume in much bigger extent then this.

So when it says "add xxx of water at xxx degrees" it doesn't take into account (approx) 3% thermal expansion at typical mash temperatures. If you measure volume at mash temp, you should subtract the given expansion relative to ground temp.

Anyhow, this shouldn't amount to 0.4 gallons, unless you brew big.

The simples solution would be to go into options, click advanced and adjust the grain absorption. If you have 0.4 gallons to much, just calculate it down to fl oz/oz (of grain used), and subract that number from the number already in the grain absorption box(es). But it's worth noting that this is not linear. Bigger grist sizes will give you a bigger pre boil volume, for some reason I don't understand, but only have accepted.

Offline friis

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I've mailed Brad a bit back and forth about this. And unless there is something in the conversation I misunderstood the only temp-correction BS does is from boiling down to pitch-temp. I've had a time where I was calculating thermal expansion left and right until I just didn't care about it anymore since there are other factors affecting the volume in much bigger extent then this.

So when it says "add xxx of water at xxx degrees" it doesn't take into account (approx) 3% thermal expansion at typical mash temperatures. If you measure volume at mash temp, you should subtract the given expansion relative to ground temp.

Anyhow, this shouldn't amount to 0.4 gallons, unless you brew big.

The simples solution would be to go into options, click advanced and adjust the grain absorption. If you have 0.4 gallons to much, just calculate it down to fl oz/oz (of grain used), and subract that number from the number already in the grain absorption box(es). But it's worth noting that this is not linear. Bigger grist sizes will give you a bigger pre boil volume, for some reason I don't understand, but only have accepted.

If I change the 'Pct Cool Loss' from 4% to 0%, it decreases the amount of strike water required (by about 3%).  So I'm inclined to think that the strike water volume does actually take into account the thermal expansion of the water.  Although I may be missing something.

What about the estimated pre-boil and post-boil volumes?  They are at boiling temperature, right?

Offline Oginme

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Pre-boil and post boil volumes are at boiling temperatures.  You can see this by the adjustment for thermal expansion on the 'vols' tab for the post boil volume calculation.

Volume into fermenter and trub loss are at room temperature.

Recycle your grains, feed them to a goat!