Partial Boil directions: Brewing Classic styles - a ? of gravity

In Jamil Z. and John P.'s recipe book, there are instructions for performing a partial boil (for those of us still stuck with 5 gallon brew pots), but there is one part of the instructions that are unclear to me. They say that the wort that is boiled needs to be the same gravity as the target OG, and that the steeping grains need to be factored into the boil gravity too (so that the pre-boil extract is less than an even 50% of the total bill). The calculations for figuring this are, for the recipe I am working out, as follows:

2.65 lbs (steeping grain) x 24ppg/3gal = ? (gravity points at 70% yield)

then you are supposed to take those points and subtract them from the target gravity, and then use that gravity number to determine the amount of extract you need, with another equation I don't understand.....The math kills me. Is all this really necessary? How much of a difference will it make if my boil gravity is little different from the final gravity? thanks in advance for your help.

It seems as though there is misreading here or something? Or I am misunderstanding. By definition the only possible quantity of wort that can have the same gravity as the target OG is the full final quantity of wort.

MAybe they were talking about Gravity Units or points? In that case the GUs do not change during boiling or dilution. 250 GUs = 250 GUs whether you have 3 gallons or you have diluted it to 5 gallons. But for this example your 3 gallon boil would have a SG of 250 /3 = 1.0833 and your diluted final quantity would be 1.050.

So basically you need to calculate the total number of GUs required based on the fermentables you are adding to your beer. If your target is 1.050 then you will need 250 GUs for a 5 gallon batch. LME add ~ 38 pts per pound, LME adds ~45, Steep grains add 34*.7= 26 pts per pound, sugar ~42 pts per pound, etc, The 250 points can be any combination of the above. And one way to make sure that you have it right midboil is to take a gravity reading and multiply by the number of gallons.


LMAO! I just read your final question! Forget the math, use a program to calculate your recipe follow the directions. The only time the above math is critical is when you do AG.

Forget the math on that part - it's an awesome book.

in fact to make it easy I've done a lot of math in that book and when adding LME just put in 1/3 to start and the other 2/3 with 10 minutes left.

The math is there if you want to get REAL picky but is not needed to make their great recipes. I'm drinking their West Coast Blaster right now and loving it.

Basically, the book is saying if you are going to do a smaller boil, keep the gravity the same, so hold back on all of the extract until the end. Steep all of your grains and add enough extract to bring the gravity up the the recipe's OG, then do the boil. At the the end add in the rest of the extract and top up with the remaining water.

If you are doing say a 3 gallon boil, use half of the extract (since the recipe book is based on 6 gallons post boil). If you have any significant portion of the gravity coming from steeped grains, use less than half of the extract.

Ah I see, they are trying to help you with hops utilization but even then you don't have to worry too much. Just follow the recipe except that, like Grinder says, you want to add most of your extracts very near the end of the boil. Extract has already been cooked to within an inch of its life so ideally you don't want to cook it more. If you have steeping grains in the recipe then just wait until the end to add all of your extract. The boil is then primarily to solubolize and incorporate the acids from the hops.`

Thanks guys. I feel comfortable just eyeballing it (or using the 1/3 at start idea). I am brewing up the 'tropical' version of the Foriegn Extra stout and I would like to actually hit the target OG with reasonable accuracy this time. the last recipe I brewed up from the book, I somehow overdiluted with water and ended up .018 below even though I used .5 gallons less than the recommended amount. arrgg. It turned my nut brown into a mild, I think. oh well. I am working myself up to all-grain, but I'm not there yet. this will be brew number 6 for me.

1. The reprobate stout recipe has a pre-boil gravity of 1.061
2. Convert the pre-boil gravity to Gravity Units per gallon (Subtract the 1 and then multiply the decimals by 1000) = 61
3. Multiply GU per gallon (step 2) by the pre-boil wort volume in gallons. This gives the GU's required. Assuming a 3 gallon boil this gives 61 * 3 = 183 GU's
4. Calculate the # steeping grains 1.0 + 0.75 + 0.75 = 2.5#
5. Multiply the # steeping grains (step 4) by 24. This gives the GU's contributed by the steeping grains. 2.5 * 24 = 60
6. Subtract the steeping grain GU's (step 5) from the GU's required (step 3) This gives the GU's to be contributed by the extract) 183 - 60 = 123
7. Divide the extract GU's (step 6) by 36 to calculate the # LME to be added at the start of the boil. 163 / 36 = 3.4# (as near as makes no difference).
8. Add the remaining 6.4# LME about 10 - 15 minutes from the end of the boil.

I hope the above explanation makes sense. At least it uses units consistently.

-a.

ajf said:

1. That brew has a pre-boil gravity of 1.061
2. Convert the pre-boil gravity to Gravity Units per gallon (Subtract the 1 and then multiply the decimals by 1000) = 61
3. Multiply GU per gallon (step 2) by the pre-boil wort volume in gallons. This gives the GU's required. Assuming a 3 gallon boil this gives 61 * 3 = 183 GU's
4. Calculate the # steeping grains 1.0 + 0.75 + 0.75 = 2.5#
5. Multiply the # steeping grains (step 4) by 24. This gives the GU's contributed by the steeping grains. 2.5 * 24 = 60
6. Subtract the steeping grain GU's (step 2) from the GU's required (step 3) This gives the GU's to be contributed by the extract) 183 - 20 = 163
7. Divide the extract GU's (step 6) by 36 to calculate the # LME to be added at the start of the boil. 163 / 36 = 4.5# (as near as makes no difference).
8. Add the remaining 6.3# LME about 10 - 15 minutes from the end of the boil.

I hope the above explanation makes sense. At least it uses units consistently.

-a.

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I think there are a few math errors here.

What is "183-20=163"

Are you saying that you need 10.8 lbs of lme? That's what I count looking at steps 7 and 8.

To figure total GUs needed you multiply total target gravity by total final volume in gallons. Not the partial boil volume .

I don't think there are any math errors, but I did turn over two pages, and the figures refer to the Reprobate stout, rather than the foreign extra stout. There is also an incorrect reference. Sorry. I will edit the original post to correct the reference and identify the correct recipe.

Here are the adjusted figures using the recipe you are using:

1. That brew has a pre-boil gravity of 1.060
2. Convert the pre-boil gravity to Gravity Units per gallon (Subtract the 1 and then multiply the decimals by 1000) = 60
3. Multiply GU per gallon (step 2) by the pre-boil wort volume in gallons. This gives the GU's required. Assuming a 3 gallon boil this gives 60 * 3 = 180 GU's
4. Calculate the # steeping grains 0.75 + 10 oz + 10 oz + 0.5 = 2.5#
5. Multiply the # steeping grains (step 4) by 24. This gives the GU's contributed by the steeping grains. 2.5 * 24 = 60
6. Subtract the steeping grain GU's (step 5) from the GU's required (step 3) This gives the GU's to be contributed by the extract) 180 - 60 = 120
7. Divide the extract GU's (step 6) by 36 to calculate the # LME to be added at the start of the boil. 160 / 36 = 3.4# (as near as makes no difference).
8. Add the remaining 6.6# LME about 10 - 15 minutes from the end of the boil.

Hopefully, that answers the question "What is 183-20=163"
The 10.8 lbs referred to the reprobate stout. It is now adjusted for 10 lbs

The whole point of the calculation is to start the boil with a pre-boil gravity equal to that specified in the recipe. It has nothing to do with the final volume or the total GU's needed. The late extract addition and the top up water adjust for the total GU's and volume.

-a.

If you read the Hops Utilization chart in Papazians TCJOHB it recommends/states that 1 gal of water and 1 lb of DME is about 1.040 (BYO mag says 1.045) and 1 oz of hops boiled for 60 mins is about the max for extracting hop bitterness.

I've been using this formula since the mid 90s...1 gal water to 1 lb of DME, 2 gals for 2 lbs, etc.

That is true, but the recipes in that book are all based on LME (1.036 pppg), and the purpose of the calculation is not to extract the maximum bitterness, but to replicate the conditions generated by a full boil.

-a.

ajf said:

I
[*]Multiply the # steeping grains (step 4) by 24. This gives the GU's contributed by the steeping grains. 2.5 * 24 = 60
[*]Subtract the steeping grain GU's (step 5) from the GU's required (step 3) This gives the GU's to be contributed by the extract) 180 - 20 = 160
[*]Divide the extract GU's (step 6) by 36 to calculate the # LME to be added at the start of the boil. 160 / 36 = 4.5# (as near as makes no difference).
[*]Add the remaining 5.5# LME about 10 - 15 minutes from the end of the boil.[/LIST]Hopefully, that answers the question "What is 183-20=163"

The 10.8 lbs referred to the reprobate stout. It is now adjusted for 10 lbs

The whole point of the calculation is to start the boil with a pre-boil gravity equal to that specified in the recipe. It has nothing to do with the final volume or the total GU's needed. The late extract addition and the top up water adjust for the total GU's and volume.

-a.

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But what is "183 - 20 = 163"? where does the "20 " come from? You say step #5 but I see no "20" there at all. Should it be "60?"

I gotcha now on the calcs. I don't remember this particular calc from when I was doing extract but I will say that I disagree with the advice that they are giving (not you. You have explained what they are saying well.) I think you should always keep LME to a minimum until the latest possible moment. Like I said before extract has already been cooked to within an inch of its life. More cooking can not be good for it. My advice is do late late late addition extract (as late as possible. If I use it, which admittedly is rare because I hate it, I do it at flameout.) Then adjust hops accordingly based on what Berrsmith tells you.

Duh

I didn't do very well did I?

Yes it should have been 183 - 60 or 180 - 60

Previous posts corrected.

If you have Beersmith, then I would agree that it is easy to adjust the hops to get the same IBU's. If you don't have software, then it makes some sense.

-a.

I'm actually going to reply to my reply. I said before that I hate extract and that is not strictly true. Once I learned that I could do my extract additions at flameout my beers got better and I stopped disliking extract so much. As long as it is fresh then the only compromise is that your beer will turn out darker than otherwise. And this only becomes an issue when competing.