Partial Mash Efficiency Dropping from Pre-Boil to Fermenter

[Dlawrence529]

I brewed a partial mash recipes using BIAB method last weekend. I mashed all my grains and then added LME in the last 15 minutes of the boil.

I tried calculating my efficiency using Brewer's Friend (https://www.brewersfriend.com/brewhouse-efficiency/). I am coming up with 57.4% efficiency (not great) based on my readings after pulling the bag at the end of the mash. I am coming up with 34.4% efficiency based on my readings going into the fermenter. Is this normal to see a drop in efficiency between these two readings?

Does anyone have any insight into how to read the analysis sheet for a can of LME? I would like to run the calculation by hand to verify the 34.4% efficiency.

Readings at the end of mash: V=3.0 gallons, SG=1.037 (measured with refractometer)
Readings going into the fermenter: V=5.0 gallons, SG=1.038 (measured with hydrometer)

My grain bill is:
4.00 lbs Pale 2 Row
0.50 lbs Caramel 20
0.50 lbs Aurora Mills Spelt
0.25 lbs Cara-Pils
3.3 lbs Briess CBW Golden Light (http://www.brewingwithbriess.com/Assets/PDFs/Briess_PISB_CBWGoldenLightLME.pdf)

I believe the LME was stirred in well (none burned to the bottom of the kettle)

 

[cswis86]

How are you measuring the volumes? The markings on the plastic buckets aren't accurate. Plus you added 2 gallons of water and likely lost a 0.5-1 gallon of wort while transferring to the fermenter so I'm not surprised the efficiency dropped. I'd focus more on increasing your partial mash efficiency (crush, stirring, sparging) and less on the quality of the LME. Or better yet, don't even worry about efficiency and just add a pound of 2 more of 2-row next time you brew.

 

[Dlawrence529]

I definitely need to work on that efficiency. This was my first attempt at mashing outside on a propane burner vs my induction burner that I use inside. I struggled to maintain steady mash temperatures. I have some reflectix insulation coming for my next batch.

My mash volume was measured from the markings on my Spike kettle. My fermenter volume was measured from the markings on my SS Brewtech Brew Bucket. I'm assuming both of these are reasonably accurate but haven't verified that.

I tried running the efficiency calculation by hand assuming the LME provided 36 ppg. I got a maximum of 62 points in a 5 gallon volume. With a measured SG of 1.038 going into the fermenter, shouldn't my efficiency be 38/62=61.3%?

The Brewer's Friend calculator is giving a maximum of 63 points, but giving an efficiency of 34.4%

 

[cswis86]

That makes sense to me... What did you estimate you OG to be? Is the 1.038 way off from what you expected?

 

[Dlawrence529]

This is a kit from my LHBS. It lists the OG as 1.050 to 1.055.

Ive only ever brewed pre-made recipe kits. This is my first attempt at tracking efficiencies. Im looking at trying to make my first recipes in the coming months and I am trying to collect some of the data to put into online calculators.

 

[cswis86]

Yeah I'm not sure what went wrong. Maybe next time you can brew an all grain kit. That way you can get rid of LME as a variable and find out if it's something else in your brewing process.

 

[RM-MN]

I definitely need to work on that efficiency. This was my first attempt at mashing outside on a propane burner vs my induction burner that I use inside. I struggled to maintain steady mash temperatures. I have some reflectix insulation coming for my next batch.

Since you are doing the mash in a bag, mill the grains finer. Use a blender if necessary. Then don't worry about the steady mash temps. They only matter while conversion is going on and with the very fine milling the conversion will be over before the temperature drops enough to matter. From then on you are extracting sugars, flavor, and color and that can happen at about any temperature.