As stated in a previous post, my efficiency on my last batch was shotty. I took a look at all 11 of my all grain brews and the efficiencies I've had, and they are always jumping. My first batch, a Black IPA, I got 66% from 13# of grain, using US Pale base malt. The second, an English Bitter, I got 83% from 8# of grain, Marris Otter base. The third and fourth, both Wheat beers, I got 76% from 19#, on a split batch, 65% Wheat, 35% Pils, batch 5 was a sour of the remaining wort from that mash, in which I hit (I assume) about 78%. Batch 6, a Saison, was 70% from 9.75#, Pils base. Batch 7, same day, a second Saison, 76% from 8.25#, Pils base & 25% Rye. Batch 8, a Mild, 72% from 8#, Munich I & Victory base. Batch 9, a Lambic, 75% from 11.5#, Pils, Vienna, and Wheat. Batch 10, same day, a Fresh Hop IPA, 68% from 13.5#, US Pale base malt. Batch 11, a Brown, 62% from 14.5#, US 2Row base. As you can see, there isn't any real consistency in my efficiency, so I decided I need to actually get the process refined and find my efficiency. I will be conducting an experiment to find out my volume losses and efficiency.
One of the factors that I believe is effecting my efficiency is related to grain crush. The crush of the grains usually causes fluctuation like what I am seeing. The reason for this is that the starches in a kernel of malt need to be converted into sugars in order to make beer. The better your crush, the easier it is for the water and enzymes to reach all the starches and convert them; inversely, the coarser/larger the crush on the malts, the more difficult it is to convert the starches. Since I crush my malts at the home brew shop, I am at their mercy as far as my crush goes, that is, unless I want to drop $150 on my own grain mill. To help with this issue I am going to send the malts through the mill twice which should give me a nice crush, and still leave the hulls intact for filtering.
The other factors have to do with my process. I batch sparge, which means that I drain my mash tun dry after mashing, and then add my sparge water to the grains, and drain again. It is a much easier process, and much less time consuming, as well as requires no extra equipment. This is compared to fly sparging which requires you to drain the mash part way, slowly, and then at the same rate of flow, add your sparge water to the mash tun while avoiding channeling (holes boring through the grain bed allowing sugarless water to drain) and tannin extraction from pH drops. In fly sparging you allow it all to drain until you reach your volume and let the remaining liquid stay behind. In batch sparging leaving the liquid (containing your sugars) behind hurts efficiency. This is one of my huge problems aside from crush. Out of the 11 batches I've done, I have yet to actually do the math to know my system. I have added extra sparge water to the mash tun in order to avoid under shooting my volume, and have never actually figured out how much of my strike water is absorbed by the grains and left behind in dead space in the MLT.
In order to refine my process and avoid the issues of leaving behind sugars, I am going to conduct an experimental batch. For this I am going to use 13# of malt which is a good mid range amount that should give about 1.062 for 5.5 gallons of beer at 72% efficiency. I actually have a recipe that needs 13# of malt that I already have the hops for so it will be cheaper to make considering I will only have to pay about $20 for malt, and use yeast from my Brown Ale that I will be bottling the same day.
The plan is to test my MLT (Mash Tun) to see how much heat I lose to the walls by putting a specific amount of water heated to a specific measured temperature, and then see what the temperature settles out at once it is dumped into the MLT. The difference between these will let me know how much more temperature I need to add to my strike water to hit my mash temps more accurately.
Next I will measure out my strike water at 1.5qt/lb, a good standard grist-to-water-ratio. For 13# of grain, I will need 19.5 quarts of water, or just shy of 5 gallons. Once I measure it out, I will add my kettle additions of gypsum, chalk, Epsom Salts, baking soda, and calcium chloride, then heat it to my strike temperature (I won't need to go over this temp since adding the hot water to the MLT will pre heat it). I will then dough-in and make sure that my temperature stabilizes where I want it, using boiling or cold water to adjust. I will of course mix it with my new mash paddle that I just bought and drilled.
After an hour, I will vorlauf, and begin to run-off my wort from the MLT. Once I have drained it completely I will measure how much volume I have for my first runnings. The difference between the 19.5qts of strike water and the volume I have will tell me how much volume I lose to absorption for 13# of grain. I will record this number and divide it by 13 to see how much volume I lose to 1# of grain (roughly, different grains may absorb different amounts). This will give me a good amount to shoot for on each batch, and allow me to estimate how much I will lose per batch and measure my sparge water accurately so none is left behind.
Next I will take the volume of my first runnings and subtract them from the pre-boil volume I want, in this case, 6.5 gallons or 26 quarts. I will then add my sparge additions, heat the sparge water to 185*F, and then add it to the grains. After it settles back out, about 15 minutes, I will vorlauf then drain the MLT. This should give me exactly 28 quarts. At this point I will give it a good stir and pull a sample from the kettle. I will cool this sample while I heat the main wort towards a boil. Once the sample gets to a temperature below 80*F, I will measure the gravity of the wort to see what my mash efficiency is. I will adjust for temp, and then do the math to figure out what pre-boil gravity should be for 6.5 gallons which is 1.052 (62GU X 5.5gals = 341 / 6.5gals = 52GU). This will tell me my efficiency from my mash, and I will add the sample back to the kettle - waste not, want not.
If I am a tad shy of 26qts, I will add water to get to that volume so I can accurately measure how much I lose to the boil. To get this figure, I will bring the wort to a boil, add the bittering hops, and boil for 60 minutes, adding the additional hops and whirfloc to the kettle when they need to go in. At the end of the boil I will chill my wort to 62-65*F, then remove the chiller. The amount of wort left in the kettle will be subtracted from the pre-boil volume, this will give me a good estimate of how much volume I lose to evaporation (their will be fluctuations in this amount each time based on vigor of boil, temp, humidity, etc.).
Next I will run the wort off into the fermenter. The total volume in the fermenter will be deducted from the kettle volume after chilling to give me a good estimate of how much volume I lose to hops, trub, and dead space in my keggle. Once this is done, I can calculate my brew house efficiency, which will tell me the efficiency I get based on how much grain I use, how much sugar I will get from it, and how much wort and sugars I lose to my system, ie, lost to MLT, boil, and kettle. It's possible that my mash efficiency will be 75%, but once loss to kettle is factored in my brew house efficiency will drop to 72%, ie, 5.5 gallons post boil of 1.065 wort, but only 5.25 gallons in the fermenter of 1.065 gals, for instance.
Once I have this information I can accurately build a recipe based on my efficiencies. I can input my desired fermenter volume at, say 72%, and know how much post-boil volume I need to get that volume, and then how much pre-boil volume I need. Taking the amount of grains, I can factor for absorption losses, and accurately forecast how much volume I will get in my first runnings, and this will let me calculate the exact amount of sparge water to get to the proper pre-boil volume. Hopefully this will all solve my efficiency jumps. I will, of course, post my findings here after I do this experiment tomorrow.