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Old 05-28-2008, 12:57 PM   #1
JMD87
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Default Partial Mash - Calculating Efficiency

When you calculate efficiency of a partial mash, I'm assuming you can only do a post-boil/post "top-off" hydrometer reading for an accurate calculation?

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Old 05-28-2008, 07:21 PM   #2
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Also, correct me if I'm wrong, but it seems if I really want to nail my efficiency, or make it seem like I nailed my efficiency, I can just top off with less than 5gal, and add water until I hit the gravity I'm looking for?

I feel like I'm cheating! Of course proportionally it wouldn't be the same as if I got a decent efficiency on the sparge and then topped off to hit my gravity.

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Old 05-28-2008, 09:21 PM   #3
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Message acknowledged, but I'm not sure I can answer for you. I skipped from full-boil extract batches straight to AG. If anything, I'm giving your question a bump here.

BrewSmith's PM brewhouse efficiency calculator looks exactly like its AG version. It does ask you for the SG of the wort as it comes out of the mash in addition to the OG of the entire batch. Bring a well-mixed sample down to room temp before reading the SG! Any reading over about 90*F is pretty much worthless, as hydrometers can't measure precisely enough for the temp adjustment.

Hopefully a guru can answer this fully for you.

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Old 05-29-2008, 07:11 AM   #4
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When I was doing PM brews I had a pretty good technique down to ensure that I nailed my OG

You can read about it here.

It does require you do have excess extract on hand though.

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Old 05-29-2008, 03:13 PM   #5
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I have one procedure and one instrument that make this easy as pie:

1. Procedure. I combine PM with late-extract. Since I boil on my electric kitchen range, I don't/can't do full-wort boil without splitting the sweet wort. I find that a complete PITA, so I run off the wort from the partial mash to my kettle until I get 3.5 gallons (which is on the upper edge of the "get it to rolling boil" limit for my stove). I boil this wort with the hops and add the extract late - just like the all-extract or extract-with-specialty-grains procedure.

2. Instrument - Refractometer. Get one. If you're going to invest hundreds of dollars in AG equipment, spend another fifty and get a refractometer. The removal of hassle will pay for it many times over. Hydrometers are for after yeast is pitched.

Using this method, if I'm shooting for a boil gravity of 1.035, I can calculate efficiency by the malt bill, liquor volumes, etc. I use the refractometer to instantly tell me what gravity my wort is. Then I add extract to make up the rest of the OG.

Make sense?

Bob

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Old 05-29-2008, 04:17 PM   #6
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So I assume Beersmith has a pre-boil gravity as well as a post top-off gravity?

I guess my question is more along the lines of, great you nailed your pre-boil gravity... but what if you put too much water in the wort post boil? Wouldn't you rather put in a gallon or so less top off water then you're supposed to, take a gravity reading, and then add water to hit your marks?

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Old 05-29-2008, 04:28 PM   #7
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Quote:
Originally Posted by JMD87 View Post
When you calculate efficiency of a partial mash, I'm assuming you can only do a post-boil/post "top-off" hydrometer reading for an accurate calculation?

You should be able to do a eff. check on your PM runnings. If you're actually mashing, and not just steeping, you should be still following a mash schedule that has a potential of extract based on the amount of grist you're using. Just take a hydrometer reading of the mash runnings, corrected for temperature of course, before adding any top off water or malt extracts.
The "How To Brew" instructions. Works the same for PM vs. AG. You're still doing a mash.

ETA: Since you're doing this pre-boil you can toss the sample back in the pot, or just take the reading right in the mash collection vessel, since you'll still be boiling it afterwards. No wasted that way.
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Last edited by FatDuc; 05-29-2008 at 04:30 PM.
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Old 05-29-2008, 05:45 PM   #8
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I am using a kit, so I'm not sure they included a mash schedule. They also did not provide ingredients/weights so I cannot put it into Beersmith.

I suppose I'll just use this one to get some practice in mashing, and then swith to AG and not worry about it anymore. I can get a 48qt SS pot for around $80. That's my next buy for sure.

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Old 05-29-2008, 07:14 PM   #9
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Calulate your efficiency of your mash/sparge runnings. Obviously you'll need to accurately measure the volume of your preboil runoff and the gravity (make sure the same is taken after a good stirring and get your sample temp down under 90F). You can do this post boil/post topoff but you really should subtract the potential of the malt extract because its going to skew your numbers towards higher efficiency.

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