Pre Boil Gravity Calculation

[JakeFegely]

I'm getting ready to do my first all grain brew. The recipe is based on Dude's Celebration IPA. Beersmith info is below. I intend to take a gravity reading after lautering, so I can make an adjustment if needed.

My question is what preboil gravity to expect. Since the recipe calls for 5.25 gallons at 1.062, I expect my preboil gravity times the preboil volume should equal 5.25 (62) = 325.50. (Total sugar shouldn't change during the boil).

The problem is that BeerSmith brewsheet tells me to expect a preboil volume of 6.25 at a gravity of 1.057. 6.25(57) = 356.25. I don't know why Beersmith is coming with something other than 325.50.

One possibility is that I have set the preboil volume at 6.25 gallons because I am using a 7.5 gallon brew pot and don't want to risk a boil over. Is it possible that with the amount of grain and the estimated efficiencies, the first 6.25 gallons out of the tun will give me more sugar than I need? If so, I suppose I could cut back on the grain, or since this is AG #1 (and I have no idea of my efficiency), just stop the lauter at 5.75 or 6 gallons and check gravity. If I have enough sugar, top off with water. If not continue draining the tun.

Any thoughts would be appreciated.

Jake

Type: All Grain
Date: 3/9/2011
Batch Size: 5.25 gal
Brewer: Jake Fegely
Boil Size: 6.25 gal Asst Brewer:
Boil Time: 60 min Equipment: Brew Pot (7.5 gal) and Igloo Cooler (10 Gal)
Taste Rating(out of 50): 35.0 Brewhouse Efficiency: 75.00
Taste Notes:

Ingredients

Amount Item Type % or IBU
10.50 lb Pale Malt (2 Row) US (2.0 SRM) Grain 86.89 %
1.00 lb Caramel/Crystal Malt - 80L (80.0 SRM) Grain 8.28 %
0.58 lb Cara-Pils/Dextrine (2.0 SRM) Grain 4.84 %
1.00 oz Centennial [10.00 %] (Dry Hop 7 days) Hops -
1.00 oz Chinook [13.00 %] (Dry Hop 7 days) Hops -
1.00 oz Chinook [13.00 %] (60 min) Hops 36.0 IBU
1.00 oz Cascade [5.50 %] (Dry Hop 7 days) Hops -
1.00 oz Centennial [10.00 %] (15 min) Hops 13.7 IBU
1.00 oz Cascade [5.50 %] (15 min) Hops 7.6 IBU
1 Pkgs California Ale (White Labs #WLP001) Yeast-Ale



Beer Profile

Est Original Gravity: 1.062 SG
Measured Original Gravity: 1.065 SG
Est Final Gravity: 1.014 SG Measured Final Gravity: 1.005 SG
Estimated Alcohol by Vol: 6.29 % Actual Alcohol by Vol: 7.84 %
Bitterness: 57.2 IBU Calories: 287 cal/pint
Est Color: 11.4 SRM Color: Color


Mash Profile

Mash Name: Single Infusion, Medium Body, No Mash Out Total Grain Weight: 12.08 lb
Sparge Water: 3.97 gal Grain Temperature: 72.0 F
Sparge Temperature: 168.0 F TunTemperature: 72.0 F
Adjust Temp for Equipment: FALSE Mash PH: 5.4 PH

Single Infusion, Medium Body, No Mash Out Step Time Name Description Step Temp
60 min Mash In Add 15.12 qt of water at 165.9 F 154.0 F



Mash Notes: Simple single infusion mash for use with most modern well modified grains (about 95% of the time).

 

[CPooley4]

I'm on an itouch right now so can't run it for you. However, the link in my signature is my brew chart. It will help you figure this out if you plug everything in. Use the recipe sheet to plug in your recipe and you can then use the brewday tab to handle the rest of the math. It's really nice to have on brewday as it calculates all of the potential adjustments for you. All you really need to do is concentrate on brewing and make sure to measure accurately. If you have questions don't hesitate to ask.

 

[JakeFegely]

Thanks Cpooley4, there is a lot of good info in your spreadsheets that will be helpful.

However I'm trying to make sure I understand the processes and some of the math behind the processes. The better I understand, the easier it will be to make adjustments on brewday (or for later batches).

I assume I am correct that preboil volume times preboil gravity should equal recipe volume times recipe gravity (OG).

What I don't understand is why BeerSmith comes up with different results for those 2 values. I doubt I found a bug in BeerSmith - it's much likely that I am missing something.
Any ideas on what I'm missing would be appreciated.

Thanks

 

[CPooley4]

Yes, you are correct about that.

For instance:

7.5 gallons preboil at gravity of 40 = 300 gravity points

300 divided by 6 gallons = 50 gravity points

50 gravity points multiplied by 6 gallons = 300 gravity points

I've never had Beersmith so it's hard for me to comment much further. I'm sure it's just something in the information you've used to setup your system in Beersmith is all. I doubt it has much to do with what you are setting your preboil volume at. The sugars you extract should be what is needed per the recipe and efficiency you are plugging in. It should assume that you will collect 6.25 gallons preboil from the mash assuming the efficiency you are assuming and will boil it down to your target volume.

Good luck.

cp

 

[JakeFegely]

Thanks for the response. I did figure out the discrepancy. In the equipment details there is a field for loss to trub and chiller. That had defaulted to .5 gallon. When I set that to zero, pre-boil and post-boil gravity points were identical.

So the software is telling me to collect extra sugar for those losses, which makes total sense. So now I can go over-analyze the next step of my first AG brew

I assume there is some way to get these smilies to be pictures instead of text????

 

[JakeFegely]

Oh, they become pictures after you post

 

[CPooley4]

Glad you figured it out. Good luck with that first all grain. Hope it all goes smoothly for you.

cp