I'll crush as I normally do, which is pretty fine, but I'm not trying to make flour. I already get efficiencies in the mid to upper 80's. So I'd like to think my crush is pretty fine. I'm hoping I do show full conversion in well under an hour.... 30min would be great, but I'm still doubting it. I mash thin (1.5 - 2qt/lb) and continue to read that a thinner mash will lead to higher conversion and efficiency, but is a slower process due to the dilution of enzymes in the thinner mash.
I'll give it a shot this weekend using the same timeline for gravity checks as the OP and report back next week.
I've seen it mentioned more than once that the thinner mash makes the process slower but finding exactly what they mean by slower is hard. Here's a bunch of info from a noted beer researcher. See what you can make of it.
"The concentration of the mash (water to grist ratio) can have a significant impact on the mash performance. Very thick mashes ( < 2 l/kg or 1 qt/lb) are difficult to stir and extract recoveries are reduced while starch conversion is slowed [Briggs, 2004].
A wide range of mash concentrations may be used in brewing. Traditional English mashes for example tend to be rather thick (2-2.5 l/kg; 1 - 1.25 qt/lb) while German mashes tend to be on the thinner side (3.5 - 5 l/kg; 1.75 - 2.5 qt/lb). One reason for the difference is the equipment that these mashes are used in. Traditional English brewing uses a single unheated mash tun that was also used for lautering while German brewers used directly heated mash vessels that require stirring the mash. The mash also has to be pumped from and to a decoction vessel and the lauter tun.
The amylase enzymes are more stable in thicker mashes (Figure 8). Which is especially important to the more heat liable β-amylase and as a result thicker mashes give more fermentable worts than thinner mashes when mashing at high mashing temperatures [Briggs, 2004]. But while thick mashes offer better protection for the enzymes, they also inhibit the enzymatic activity through the reduced availability of free water and the sugars acting as competitive inhibitors [Briggs, 2004]. In addition to that the gelatinization of starch is also slower and happens at higher temperatures in thick mashes and as a result thinner mashes are known to give more fermentable worts at normal mashing temperatures.
The results for mash thickness were somewhat surprising. Contrary to common believe no attenuation difference was seen between a thick mash (2.57 l/kg or 1.21 qt/lb) and a thin mash (5 l/kg or 2.37 qt/lb). Home brewing literature suggests that thin mashes lead to more fermentable worts, but technical brewing literature suggests that the mash concentration doesn't have much effect in well modified malts [Narziss, 2005]. Briggs cites data that doesn't show a change in fermentability when the mash thickness is changed [Briggs, 2004]. This was confirmed by these eperiments where all the data points were on the same curve that had already been established in the temperature experiment.
Note, that the experiments for the 2.57 l/kg mash were run twice because the initial experiment resulted in a small mash volume that lost 5 degree Celsius over the duration of the mash. To keep the temperature drop between the experiments the same the mash volume was increased and the result was a 2 degree Celsius temperature drop which matched the temperature drop for the 5 l/kg mash. But in the end that didn't make a difference.
A significant difference was however found in the efficiency. The brewhouse efficiency of the thick mashes remained almost constant between 58 and 60% over the temperature range of the experiments, but the brewhouse efficiency for the thinner mash showed a strong dependency on the temperature and was always better than the efficiency of the thick mash. That leads to the conclusion that thinner mashes perform better and allow for better extraction of the grain. Briggs also reports that thinner mashes can convert more starch but that most of the conversion potential is reached at a water to grist ratio of 2.5 l/kg [Briggs, 2004] "
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