I mashed 6lb of malt with 4.125gal of water, 2.75qt/lb ratio. The initial mash temp was 152F and it dropped to 148F during the course of the mash. Each time I would take a small sample for refractometer testing, then stir the mash. I tested the sugar content every fifteen minutes for two hours and got the following data:
Min degrees Plato
15 6.5
30 9.0
45 9.8
60 10.4
75 10.8
90 11.0
105 11.3
120 11.3
I mashed out with 1/2gal of boiling water, although this only brought the temp up to 155F. I got no additional sugars from the mashout addition.
I calculate that I got roughly 86% conversion by 105 minutes, and a preboil efficiency of 74%.
What was the grist? I don’t know that I’ve ever mashed quite that thin, but I’m used to seeing conversion at ~100% after 60 minutes. I’d wager the low temperature had an effect too though.
The grist was 5.0lb of Rahr 2-row, 0.5lb of crystal 40 and 0.5lb of a blend of specialty malts I’d put together for another beer but didn’t use. The beer is an APA, with Chinoook for bittering and a blend of Amarillo, Cascade, Columbus and Sincoe for the late additions.
Preboil gravity was 1.040 (roughly 4gal), postboil I got 3.0gal of 1.052 OG. Didn’t lose much volume to the pellet hops because I ran it through a wire mesh screen.
I assume my crush was responsible for a less than 100% conversion. The efficiency was affected by the fact that I added 4.625gal total, and with 0.125gal/lb left in the grain I should have had nearly 84% efficiency with 100% conversion.
I’ll let you know when I get one that far, but I’m guessing it’ll be no different since I can still target my OG/FG using length of mash and mash temp.
Yes this is equivalent to BIAB with no sparge, I’ve seen BIAB done with a rinse but I don’t know if its common. My bag is just a MLT with braid.
I also don’t know that BIAB necessarily has you use an unconventional mash ratio like the 2.75qt/lb I’m using. This is why I’m reporting this info, simply to expand what we think of as an acceptable mash ratio. Given enough time, it allows one to do a one step mash and lauter that I’m hoping will have no down sides.
As for the length of time it takes for conversion, I understand that this is just one data point and that the kinetics depends on crush, water chemistry and temp, among other factors. I just threw it out as a little more in-depth version of my first observations where I mashed for 2hr just to be safe.
I suppose that depends on how important it is to you to get every last bit of starch converted. for a lot of people I think something over 80% is enough. As evidence for this is the common 75% efficiency number cited by many brewers, that no doubt comes in part from a lack of 100% conversion of starches. If you consider the theoretical recovery of a mash and a sparge, you would be getting over 90% all the time.
If you aren’t getting full conversion in an hour I think your mash chemistry may be a little out of whack. As long as I get my pH in range I have >90% conversion when I start recirculating at 45 min.
I don’t agree that sub-90% conversion indicates a problem with pH. I am treating my water all the time now and checking with a pH meter, and still getting average efficiencies that are partly due to a less than complete conversion.