[tomsawyer]

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%.

[a10t2]

Good stuff. Thanks for taking the time to do it.

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.

[tom]

Thanks Lennie,

What gravity did you get?

[tomsawyer]

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.

[oscarvan]

0.5lb of a blend of specialty malts I'd put together for another beer but didn't use

I've done that.... I'm always worried that it will be the best beer ever and I won't be able to figure out what was in there....

[dcrawlins]

Sounds like an Australian brew in a bag method.  It is a no sparge method that works well.  I have used it for big brews to save time.

[andyi]

Thanks for  the information.

How is the body/mouthfeel of the finished beer with that thin a mash.

[tomsawyer]

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.

[ccarlson]

I always mash longer than 1 hour. One hour is not long enough, IMO.

[a10t2]

I always mash longer than 1 hour. One hour is not long enough, IMO.

Long enough for what?

[ccarlson]

Complete conversion.

[tomsawyer]

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.

[a10t2]

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.

[ccarlson]

I don't have the means to test PH level, but by going with a longer mash I consistently get efficiencies in the upper 80's to lower 90's.

[tomsawyer]

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.