# A partial mash question for the numbers geeks out there...

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#### Turner_Brown

##### Active Member
For now I've just been doing 5 gal partial mashes. The next batch I plan on doing the same but I'm going to try to dial things in a bit.

I'm brewing a big IIPA and I want to try to hit an OG of ~1.040 for the boil so I can get the most out of my hops. Then do a late boil extract add to hit 1.090.

This can be a little tricky since I'm confined to boiling only 4 gallons.

My question is this:

I'm using 4.2 lbs of grain. Assuming an efficiency in the high 60's...about how much water will I need for the strike mash and then for the sparge?

I plan on using DeathBrewer's method (2 pots - mash in first then soak in second for a "sparge").

Basically I want the wort to = 4 gallons and be around 1.040 for the initial boil.

OP

#### Turner_Brown

##### Active Member
My SS pot is 5 gal.

I plan on picking up an Al pot this weekend (probably about a 6 gal or so).

My other limitation is my gas stove. I think 4 gallons is at the upper limit of my boiling abilities.

#### mbird

##### Well-Known Member
I figure about 1.3 qt per lb. of grain so stike 1.3gal water at 168f. You will lose about 1/2 the water to the grain when you sparge so plan to sparge with 3.3 gal. at 180f. As far as the gravity goes, you may have to add more grain because with 2-row your at 1.037 per lb per gal less whatever your efficiency. If your efficiency is 75% than you can expect to get 1.028 per lb. per gal so you want do plan on using about 6lbs of grain.
(6lbs x 37 = 222 divided by 4 gal. = 55.5 x 75% eff. = 1.041)
mark
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OP

#### Turner_Brown

##### Active Member
I figure about 1.3 qt per lb. of grain so stike 1.3gal water at 168f. You will lose about 1/2 the water to the grain when you sparge so plan to sparge with 3.3 gal. at 180f. As far as the gravity goes, you may have to add more grain because with 2-row your at 1.037 per lb per gal less whatever your efficiency. If your efficiency is 75% than you can expect to get 1.028 per lb. per gal so you want do plan on using about 6lbs of grain.
(6lbs x 37 = 222 divided by 4 gal. = 55.5 x 75% eff. = 1.041)
mark
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Rather than mash more grains, I was thinking about adding some of the 9 lbs of LME to bump up the OG to 1.040.

#### BuzzCraft

##### Well-Known Member
My SS pot is 5 gal.

I plan on picking up an Al pot this weekend (probably about a 6 gal or so).

My other limitation is my gas stove. I think 4 gallons is at the upper limit of my boiling abilities.
First, I'd suggest that you mash as much grain as possible....I can mash 7 lbs in a 4 gallon pot using 1.25 qts water/lb for both the mash and rinse/sparge, so you should be able to get away with more. Don't worry if you end up with more wort than you can boil (which you probably won't). You can just boil it in the second pot with some more water and add your extract there, which is what I'd recommend. Once this comes to a boil, you can add you extract so that your total gravity ends up where you want it for the batch.

The best way to think of this is in total gravity units for your batch. Once you do your mash and sparge, figure out how many gallons of wort you have and figure out the specific gravity. Multiply those together and you've got the total gravity units from your mash. Let's just say you've got 4 gallons of 1.050 wort after the mash, that's 200 gravity units (4 gal X 50...just drop the 1.0 from 1.050 for this calculation and subsequent ones). For a 5 gallon batch of 1.090, you ultimately need 450 gravity units (5X90). So you'll have to add gravity units using your extract. If you're using dry extract, it gives you 45 units per pound, so you need 5.6 pounds (250/45) to hit your 1.090 for your final batch.

That make sense?? If you want to hit your gravities and especially if you have no idea what your efficiency is going to be, you really need to be able to work with this concept on your batches. It should allow you to hit your gravity within a point every time.

#### BuzzCraft

##### Well-Known Member
If you're really set on using only 4.2 pounds of grain, you should still be able to figure everything out from my previous post.

Make it easy on yourself and just boil the extract for 10-15 min in your second pot instead of adding it late to your wort boil.

#### mbird

##### Well-Known Member
Also, if your making an IPA I would suggest substituting some of the malt extract with cane or corn sugar. Malt extract tends not to finish dry enough for an IPA, with the sugar you should be able to get the final gravity down some. Consider adding 10-15% sugar. IMO
mark
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