Homebrewers Association  AHA Forum
General Category => Extract/Partial Mash Brewing => Topic started by: bbump22 on March 09, 2010, 11:26:06 PM

I have moved on from Extract brewing into Partial Mash brewing and have done several batches now. The first few, I didn't measure my preboil gravity as I was using recipes from BYO and it didn't mention anything about preboil gravity...I would still hit the Target OG within a few points. Recently, I have been using the trial version of Beersmith to generate my own recipes. The first batch I brewed, I successfuly hit the target OG beersmith estimated assuming the default brewhouse efficiency of 75%...honestly, I think I just got lucky.
On my next batch, I generated a recipe in the same manner (assuming 75% Brewhouse Efficiency), but missed my target OG by about 12 points...After entering in my preboil gravity, preboil volume, batch volume and actual OG measurements, beersmiith spit out a brewhouse efficiency of 52%...When I did the calculations by hand, I calculated an Extract Efficiency of 74% and Brewhouse efficiency of 68%. So my question is why would Beersmith give me an efficiency % so much lower than what I calculated by hand if I used the same numbers I plugged into Beersmith? I am sure it's probably something I am overlooking, but I can't quite figure it out. I've spent the last 2 days at work searching the forum's but couldn't find anything that gave me a clear reason as to why there would be such a variance.
Below is the grain bill, measurements, and calculations I generated on my own...If one of you experts could help me out so I can get better brewhouse efficiency allowing me to use beersmith to generate a recipe I would be very greatful!
Target OG based on 75% brewhouse efficiency 1.065
Actual Original Gravity 1.053
Est. FG 1.013  1.018
Grain Bill: Lbs
US 2Row 4.5
Crystal 60L 1.5
Carapils 0.5
Rye 0.75
Liquid Malt Extract 2.5
Extra Light Dry Extract 1 (Added for the last 15 minutes of the Boil)
Calculate Estimated Original Gravity
Grain Malt PPG Malt Lbs Total Available Gravity Points
US 2Row 37 4.5 166.5
Crystal 60L 34 1.5 51
Carapils 33 0.5 16.5
Rye 29 0.75 21.75
Liquid Malt Extract 36 2.5 90
Extra Light Dry Extract 44 1 44
10.75 389.75
Original Gravity Calculation (SGP) assuming 75% Brewhouse Efficiency
=((4.5*37*0.75)/5) + ((1.5*34*0.75)/5) + ((0.5*33*0.75)/5) + ((0.75*29*0.75)/5) + ((2.5*36*1)/5) + ((1*44*1)/5)
65.1625
SGP = 1.065
Caclulate Extract Efficiency
TGP (Total Available Gravity Points)
Grain Malt PPG Malt Lbs Total Available Gravity Points
US 2Row 37 4.5 166.5
Crystal 60L 34 1.5 51
Carapils 33 0.5 16.5
Rye 29 0.75 21.75
Liquid Malt Extract 36 2.5 90
9.75 345.75
Maximum Specific Gravity
=TGP/Collected Volume in Gallons
=(345.75/3.5) 98.78571429 1.099
Extract Efficiency (EE) 74%
=(Measured SG/Maximum Specific Gravity in Points) * 100
=(73/99)*100 0.737373737
Calculate Brewhouse Efficiency
Grain Malt PPG Malt Lbs Total Available Gravity Points
US 2Row 37 4.5 166.5
Crystal 60L 34 1.5 51
Carapils 33 0.5 16.5
Rye 29 0.75 21.75
Liquid Malt Extract 36 2.5 90
Extra Light Dry Extract 44 1 44
10.75 389.75
Maximum Specific Gravity
=TGP/Collected Volume in Gallons
=(385.75/5) 77.95 1.078
Brewhouse Efficiency 68%
=(Measured SG/Maximum Specific Gravity in Points) * 100
=(53/78)*100 0.679487179
So that's what I did to figure out Extract Efficiency and Brewhouse efficiency. I mainly want to know how to improve efficiency or at least make it consistent so that I can develop recipes and hit my target OG or at least within a few points. Again, thanks for any help you can offer!

I'm having a little trouble following your calculations. What was the volume you collected from the partial mash and what was your boil volume?

I'm having a little trouble following your calculations. What was the volume you collected from the partial mash and what was your boil volume?
Yeah, did you actually measure your volumes? It looks like you used 5 gallons in some of your calculations but did you actually measure it? True volumes are critical to calculating efficiency.

Sorry fellas, I should have provided more background info...but yea, i did measure my volume...I had collected 3.5 gallons at preboil. After a 60 minute boil, I had 3 gallons remaining in my kettle at which point I added 2 gallons of bottled water to the fermenter, the added the remaining 3 gallons to the fermenter bringing the total batch volume up to 5 gallons.
Also, I mashed with 10 quarts for 60 minutes with a step temp at 154, losing 2 degrees over the course of the mash. Then I batch sparged with 7 quarts with a step temp of 165. (Added water at 186 and then stirred gently and let it sit for another 15 before draining).
I calibrated my hydrometer and thermometer and used measurements on my kettle to measure the preboil volume. I took a sample directly from the kettle after incorporating the 2.5 # of LME and adjusted my hydrometer reading for temperature.
Let me know if you need any other background info and thanks for looking into this with me.

When calculating your conversion efficiency, use only the grains, not the extract. Otherwise you'll get a different result every time the proportion of extract changes. I'm guessing that's why Beersmith is giving you different numbers.
Since you collected 3.5 gal at 1.073, that's 255.5 pointgal. Factoring out the extract:
(255.5  (90 + 44))/(389.75  (90 + 44)) = 0.475, about 48% efficiency. The discrepancy is probably due to slightly different potential extract figures.

Thanks a1...any suggestions on how can I improve my conversion efficiency? Also, when creating a partial mash recipe is there a general rule to follow with regards to what % of extract should come from the mash versus how much should come from LME or DME? From what I understand the goal of a partial mash is to mash base malts with specialty malts that require enzymes from the base malts to convert their starch into fermentable sugars. Is there some ratio to use when creating recipes?

Are you sparging? Theoretically, if you're at 50% for a nosparge, doing a single batch sparge would get you to about 67%.
I guess there would be two ways to look at a minimash: mash as much grain as possible (save money), or as little as possible (minimize complexity and/or use up extract). For the former you'd want to mash all the specialty grains and much base malt as your setup could handle. For the latter you'd want to mash the specialty grains with the minimum amount of base malt needed for conversion  about one pound of base malt for every two pounds of other grains (for domestic 2row) or maybe 1:1 for lessmodified continental malts.

I did a single batch sparge with 7qrts of water at a step temp of 165. I let it sit for 15 minutes after lightly stiring the grain.

Are you mashing and sparging in a cooler or in a grainbag directly in the brewpot or something else?

I also do partial mash because I want to stay on the stove for now.
I currently mash the grain in a grain bag in 1.25 qts h2o per lb. in a pot at temp and time set by Brewsmith software. After step time, I add small amount of higher temp h2o (ttl of 1/2 brew volume) to increase temp to usully 168*. Then I move grain bag to brew pot which has the other 1/2 brew volume h2o at 168*. I remove grain and combine worts, add extract and bring to boil.
I am going to get a 5 gal cooler so that I can increase grain usage from 3 lbs to 5 lbs (my boil voume is 3.5 gal in a 5 gal pot) and so that I can recirculate the wort before going into brew pot.
Am I batch sparging correctly, and am I moving in the right direction?

Am I batch sparging correctly, and am I moving in the right direction?
Your procedure sounds good. If anything, I'd say you could save some time and effort by skipping the 168°F mashout and going straight to the sparge. Do you know what kind of efficiencies you're getting?

i use a 10 gallon igloo cooler that I modified into a lauter tun. It holds the temp great. I went with 10 because one day I hope to be doing AG batches.

No, I don't know the efficeincy yet. (no refractometer) the first real measurement I make is checking OG as I add h2o to the primary carboy. (The refractometer is on my "To Get" list along with the cooler and a small mill.)

You don't need a refractometer to check your preboil volume, just go ahead and use your hydrometer. Be sure to measure the temperature of your wort when you do take your reading, beersmith has a tool to adjust your hydrometer reading for temperature. Also this way you can check to see if your hitting your desired extraction efficiency and then adjust your malt extract addition to get your desired gravity.