A little backstory about my limited brewing history:
The first two batches I did were the same, since I do around 9.5 liter batches. I split a full size kit in half and did it twice, using the Calculator. Both times I pretty much hit my preboil gravity but my volume was a lot lower than expected. I figured it was somehow absorption related, but I wasn't sure what to set it as for my next batch because at the time I think I had some confusion with the 20C-100C expansion. I also didn't understand why increasing my strike water for the same amount of grain would fix my absorption problem without screwing up the preboil gravity. After finding this thread and reading about true/apparent absorption here and on braukaiser.com it made a lot more sense so I decided to use this calculator for this batch.
This time I did an Anchor Steam clone, converting it from a 19 liter recipe I found. I also ran it through the regular Calculator, and Beersmith, just as sanity checks. They were pretty similar.
My settings in the CE calculator:
I tried to fill in the specs for the actual grain I got but couldn't find one and didn't know the other. So I used what I thought was closest. The recipe was 91.72% Pale Ale (FGDB 80 and moisture 4) and 8.28% Crystal 60L (FGDB 73 and moisture 5.5).
Target fermenter volume was 11 L at 1.051 OG, it told me 2.731 KG total for grain.
I used Real Absorption at 1.33 (almost went to 1.41 based on my previous experience but resisted after reading the thread again)
Strike water was 21.14 L with 6 L evaporation and 2 L kettle loss.
Mashed at 152*, with a mashout to 170* after (not sure how much this helps, I'll probably try skipping it next time)
Pulled up the bag, twisted it up until the main flow slowed, then put it in a colander and pressed a plate onto it for a few seconds (not too much, it was just too hot to squeeze).
Poured that runoff into the kettle, brought it to a boil and measured (cool sample):
Preboil volume 19.58 L at 100C (expected 19.52)
Preboil gravity 1.034 (expected 1.035)
Preboil Efficiency 79.9% (expected 82.9%)
Conversion efficiency was 95%, which I am fine with at this point.
I was also doing the efficiency analysis from braukaiser.com alongside the brew so at this point I combined the grain with 5.44 L of cool water and took the SG of that, which it uses to check the lauter efficiency. The SG of this was 1.013. All the efficiencies in this spreadsheet matched the CE calculator pretty closely.
End of boil was 13.6 L at 100C (expected 13.52 L) at 1.051 for an efficiency of 83.4%. Just slightly over 13 L at 20C so it was right on.
I attribute the mismatch to measuring errors, perhaps the preboil SG was 1.035 in which case conversion efficiency would be 97.9% and preboil would be 82.3%. Those hydrometers are tough to read.
Actual real absorption was pretty close at 1.31 L/KG, so my missing preboil volume seems solved - the default value in the Calculator was just way low for me. I find the true absorption to be a better metric even though it is not immediately measurable, especially if you are using the actual potential of your grains.
I ended up with double the expected amount of loss to kettle trub (maybe time to get a hop sock), but instead of losing that extra 2 L of wort I ended up straining it and gaining 0.3 L instead for a final total of 11.3 L at 72.1% into fermenter. A huge improvement since my previous two batches were 57% and 60%.
I will definitely be using this again, so thanks for all the work.
Thanks for documenting such a good work out
I've been testing sparge water gravity as well, and I'm finding the results are good too
, on my last brew the gravity of the sparge water was exactly as predicted, previous brew it was 1 point out, which is easily within the margin of error on a hydrometer reading
I think one one of hte more interesting things is how much of a difference hop matter makes to kettle loss. For example I did a triple batch with just 15 IBUs from a 60 min additions, so not much hops... thus not much kettle loss...
and I did an APA, with 35 IBUs, 15g, 30g, 60g, 90g additions, and that one had almost double the kettle loss! perhaps a hop bag would be a great solution, but I just don't seem to get around to it