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Gluten Free Home Brewing Blog

Partial Mash vs Partial Grain - Part 2

By GFHB  -  September 22nd, 2018

The first episode in this two part blog may be found here:

In this second episode in our two part blog, we are going to review the two gluten free Amber Ales which we brewed simultaneously using the partial mash and partial grain with BIAB option brewing methods. The same grain bill was used in each batch of beer, and the amount of sorghum syrup was calculated based on the projected conversion and efficiency of each brewing method.

If you have been following us, you may recall reading our blogs about the BIAB method. Some of our earliest posts were not very encouraging, however, at that time we didn't know a lot of what we know now. What we do know now is that the diastatic power of gluten free malts is quite low, and the dilute or "thin" mash conditions of the BIAB method only adds to the low enzyme activity. Therefore, we deviated from the original plan. (A few our more regular followers are probably gasping right about now) We used the same amount of enzymes in both batches as we could confidently say we would get little to no conversion otherwise.

To our pleasant surprise, we got about 25% efficiency on the partial mash as compared to the 75% efficiency on the partial grain. But to be fair, this could be considered as more of a comparison of two partial grain batches because we used the same amount of enzymes in both batches, and conducted a 45 minute steep/mash on the partial mash. Conventionally, partial mash brewing involves steeping malt for about 15-20. However, we realize there are a lot of websites and brewers that will suggest steeping malt for up to an hour. This is where the definition of partial mash gets a little gray and why we dubbed it partial grain!

By The Numbers:

PARTIAL GRAIN (Single Infusion @ 120 minutes)

PARTIAL MASH (Steep/mash @ 45 minutes)


Final volume: 290 oz or 2.27 gal
Efficiency: +/-75%
OG: 1.058
FG: 1.014
ABV: 5.75%
SRM: 10.34
Volume of sorghum syrup: 37.5 OZ

Target was:

OG: 1.053
FG: 1.013
ABV: 5.2%

Final volume: 283 oz or 2.21 gal
Efficiency: +/-25%
OG: 1.062
FG: 1.022
ABV: 5.25%
SRM: 10.34
Volume of sorghum syrup: 52.8 OZ

If we had less unfermentable sugars:

 ABV: +/-5.96%

If we had achieved 75%:

OG: +/-1.076
FG: +/-1.015
ABV: +/-7.48%

If fermentable sugars come from sorghum syrup only:

OG: 1.044
FG: 1.011
ABV: 4.4%


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