Crush and complete draining of the MT are going to give you the biggest efficiency boost. And checking your pH with the strips is good enough to keep you in the proper range.
I’ve lost track of all the posts on this thread, but if you are able to 2x crush at the LHBS and/or can get them to tighten the gap until you get some flour, you can check to see if crush is an issue. When you clean out the MT, do you see wort sloshing around in the bottom? (Leaving a half-gallon in the MT would be an 8% efficiency hit in a 6-gal boil.)
Wow…really? I lose about 1 quart to dead space each time I drain, which makes for a 1/2 gallon total between mash and sparge runnings. What’s the best way to get the deadspace wort? Auto-siphon + mesh bag?
[edit]Ah, I guess 8% applies to first runnings, i.e. 100% / (6 gal * 2) = 8.333333333% per 1/2 gallon. So, I lose about 4% to dead space assuming I’m getting full conversion, and that I let it drain long enough once it slowed to a trickle. I let it sit for quite awhile before pouring in the sparge water, then tilted the tun and pushed the grain back to be sure the wort level was below the drain.
I double crushed the grains this round, but there was virtually no difference in appearance after the second crush. The gap at the LHBS is .045". I might see if they’ll tighten it for me if I go there again before I get a grain mill.
The dead space is accounted for only once for the entire mash, not cumulative over multiple sparges (since the wort left behind is diluted by the sparge water), so if you’re doing one sparge and leaving a quart behind, that’s not a big deal, might be worth 2-3% efficiency since it’s dilute wort. If the LHBS gap is 0.045, that’s likely the source of your low efficiency and a second crush isn’t going to make any appreciable difference - get them to run the grain through twice at 0.030 for at least the second pass and see what you get.
[quote=“ickyfoot”]
I will be sure to measure first runnings next time and see what kind of conversion I’m getting. Am I understanding correctly that mash gravity that is 100% potential for the volume means I got 100% conversion? Or, can it be over/under depending on that volume?[/quote]
100% is 100%, but the gravity at 100% will vary depending on the volume and the volume will vary with mash thickness and as sugar is dissolved.
This chart http://braukaiser.com/wiki/index.php?title=Understanding_Efficiency#Measuring_conversion_efficiency
tells you what gravity to expect at 100% conversion based on your mash thickness at the time of measurement.
Yeah, I account for volume, but I might use the chart next time. I tend to be a little flustered and on brew day and botch the calculations the first 3 - 5 times .
I’m curious, though; how is it possible to have a catch all mash gravity chart since grist composition affects the amount of sugar available? Is it because there’s usually more sugar available than first runnings can dissolve?
My refractometer was 5 points off and it was a smaller beer, that is what made the big swing. My hydrometer reads .03 high but that is easy to account for.
The catchall is an approximation, assuming 80% FGDB grist and 4% moisture (76.8% as-is). If you have a lot of specialty malt in your grist that number is going to go down and your mash gravity will be lower than what the chart predicts. You should not, however, see numbers higher than this chart if you have accurate measurements.
If you’d like to calculate the mash gravity for your specific batch, here’s how. First, find the weighted average grist extract potential (grain1eweight1 + grain2eweight2 / (weight1+weight2), then multiply by the total weight of the grist. This is the weight of potential extract in this grist. Dividing this by the weight of water used plus the potential extract will give you the %sugar of the mash, aka °P/°Brix.
For example, your recipe has 12 lbs of 6-row (75.7% extract by weight) and .75 lbs of C-60 (~73% extract by weight), so the grist has an extract potential of
(12*.757+.75*.73)/(12+.75) = 75.5%.
And multiplying by the total grist weight:
12.75*.755 = 9.63 lbs of potential extract.
Mashing with 22 quarts * 2.079 lb/qt (density of water at room temp) = 45.74 lbs of water
So the max mash gravity reading is m_e / (m_e + m_w) = 9.63 / (9.63+45.74) = 17.4°P, or about 1.071.
[quote=“ickyfoot”]
I’m curious, though; how is it possible to have a catch all mash gravity chart since grist composition affects the amount of sugar available? Is it because there’s usually more sugar available than first runnings can dissolve?[/quote]
The chart assumes 36 points per pound, which a pretty reasonable average for a lot of grain bills. If you calculate a different average for your particular grain bill, you can just multiply the expected gravity from the chart times that value divided by 36:
predicted gravity x avg. pppg ÷ 36 = gravity expected from your grain bill.
All the sugar should be dissolved in the first runnings. In fact, that chart actually assumes that to be true. The remaining sugar after the first runnings, which needs to be removed with a sparge, is actually at the same density as the first runnings but is just absorbed by the grain. Adding the sparge water just dilutes it so that more can be removed by leaving more-dilute wort behind in the grain.
[quote=“ickyfoot”]So, you use the volume of strike water, not first runnings, to determine potential mash gravity?[/quote]Right, but not just strike water, any water that you have added before taking the measurement. If you have done any step infusions or mashout additions, you want to include those. Note that Kai’s chart is based on mash thickness, which is the thickness at the time of the reading.
Would your interest in getting higher efficiency change if you got 62% with every recipe you mashed? IMO consistency is more important than magnitude when it comes to efficiency.
Slothrob, thanks for the info re: volume to use when calculating potential mash gravity.
If mid-60s is all I can get, I’ll be fine with it so long as it’s consistent and the beer tastes good. But, since I’m so new to this I feel it’s worth at least trying. Even if I my results never improve, it’s a great learning experience. Best lesson so far is to adjust the hop schedule based on measured efficiency.
Most importantly, though, when I I look to your signature I answer, “Maybe” and “Yes,” so I know I’m on the right track!
OK, I brewed again last night, and I got 72% efficiency. Woohoo! While it’s not that much better than the 68% I got my first time, it was a huge relief to see 9% better efficiency this time than last time, and hitting 70%+ was definitely a goal (75% being the target).
The differences:
I mashed low (~147 to start) by accident (forgot to pre-heat the tun), but decided to roll with it
I covered the cooler with a blanket and lost only 3 degrees
First runnings gravity was 1.070 (~82%) @ 60 degrees
Mash gravity was 1.050 (~72%) @ 6.5 gallons @ 60 degrees
OG was 1.058 @ 62 degrees
I’m not 100% positive of post-boil volume, but possibly around 5.5 gallons? Any way to calculate this based on pre-boil volume and SG?
Most importantly, though, I really combed through the crushed grains at the LHBS, and there were quite a lot of uncrushed or barely crushed kernels. I asked if they could narrow the gap, and they said no, that it would clog. I got the sense he meant the grinder, but I’ll go ahead and assume he meant the sparge . On the bright side, I got a new grinder for my b’day, so crush gap is up to me now.
You really need to be able to accurately measure your post boil volume. There’s no way to calculate it. If you’re off a bit, it can have a real impact on your efficiency calculations.
Shouldn’t it be possible to calculate post-boil volume if you know pre-boil volume, pre-boil gravity, and post-boil gravity, since the amount of sugar is constant?
OK, yeah, if you do inverse cross-multiplication, that should do it, yes?
(50 * 6.5)/58 = 5.6 gallons
AKA
(MG * MV)/OG = post-boil volume
Going into the fermenter, I probably lost at least a 1/2 gallon due to trub clogging the auto-siphon. Wish I’d thought to bust out the strainer. Oh well.
So, I’m now the proud owner of an MM3 grain crusher. I built a base and the hopper is on the way. Woohoo! In light of this new aquisition, I set out on a quest to buy a feeler gauge, only to discover that these are hard to come by nowadays (not surprising, really). The best I could find only went down to .040".
I did some research and discovered that debit/credit cards are .030" thick, which seems like a decent place to start*. Has anyone used a credit card to set their mill gap and had good results?
*Another site says .036", which would be fine, too.
[quote=“ickyfoot”]I set out on a quest to buy a feeler gauge, only to discover that these are hard to come by nowadays (not surprising, really). The best I could find only went down to .040". [/quote]Check your local auto parts store, should run you about $3 for a set.
I checked 'em all…no one has 'em, except one, but it only goes down to .040". Really lame/annoying. I’ll eventually just buy one online, I guess. If supplies arrive in time for me to brew this weekend, though, I’ll just go with the credit card and see what happens.
DUH! My neighbor is an auto mechanic. I’m sure he’ll have one I can borrow, and I’ll just mark some settings.
