Ever since moving from 2.5 gallon to 3 liter batches my efficiencies have been terrible. I was getting 70% or so on the old system and now can’t get over 55% on the small system. It’s driving me a little crazy. I’ve tried sparging with more water and boiling longer, doing two sparges, crushing past the point of mortal fear (which led to insanely poor run-offs but didn’t help my efficiency at all) and playing around with different mash-out and sparge temperatures. Nothing seems to work.

On Saturday I brewed an IPA targeting an original gravity of 1.066 but got about 1.045 at the end of an hour. So I boiled for a little while longer and got it to 1.050 and called it a beer. That brew was going to get the Pacman yeast that I had just cultured, but since it was so far off target it got some Sixpoint yeast still in the fridge. Still being tormented, I attempted another brew on Monday.

I’m actually an engineer by trade so it surprises even me that I seem to be shooting from the hip in trying to crack this nut. But it’s fun in some bizarre, self-destructive way even if it isn’t always helpful. Monday, however, would be different. Well, not really, but that was the idea going into the brew session. The logic went like this:

For some reason, all my small brews have really low efficiencies even though the larger brews had decent (i.e., livable) efficiencies. Rather than keep trying to figure out why the small brews are different, why not just formulate the recipes around those efficiencies? I can deal with an extra few ounces of grain per beer.

A not-so-exhaustive run through the old sessions showed that most of the small brews were pretty close to 50% efficient. One was about 55 % and one was 48%, but they were all pretty similar. So Monday’s session would be the same basic recipe from Saturday’s IPA, but tailored to a 50% efficiency. How could that go wrong? Well, I’ll tell you how – I still missed my 1.066 target by 8 points at 1.058 (upsetting but close enough to get the Pacman). Okay, that’s not exactly telling you how it went wrong, just that it went wrong. The reason is that I still don’t know why things are going wrong.

But I have a theory. Hear me out.

In talking about this with Michelle (who is a wonderful listener even when I’m talking about my mash efficiency dilemma) I explained that there should be no reason for such a change from one size batch to another if everything was scaled down appropriately – smaller mash tun, smaller kettle, smaller fermenters, etc. The mash temperature has been spot on, and on Saturday I was able to get a handle on the boil-off rate (3.2 quarts per hour) and use that number for Monday’s session. The question that I couldn’t answer was “What value does not scale linearly with batch size, or what value am I not accounting for?” And while I was driving to work today I think I may have hit it.

(Incidentally, my commute is where I do most of my technical thinking for some reason – both for my hobbies and for work. I should start charging my office for this time.)

The (potential) answer actually sprang from some things I’m doing at work in which I’m trying to find trajectories for different projectiles. In that particular problem, the range we’re dealing with is different from the range we typically use and I was having some trouble getting precise results because of the increased error associated with that shift. Eureka! (And you didn’t know where this story was going, did you?) Maybe my mash problem isn’t a problem with the crush or temperature, but in the accuracy of my water measurements. If I’m off by a cup or two in the larger brews it won’t really matter, but when I’m after 3.5 quarts of wort that cup could throw my numbers off more significantly.

So here’s my plan of action: Acquire a metal ruler to take measurements of the wort going into the kettle and into the fermenter. The wort into the kettle has been unmeasured up to now and the beer into the fermenter is only measured in relation to a piece of tape I stuck on the jug at the 3.5 quart level. And I’m going to brew a simple beer (not sure what kind yet, but probably a pale ale) a couple of times in a row in an attempt to really tighten up my process. Oh, and I’ll take notes as I go so that I’ll know what’s happening from one session to the next (and have something to post here). Sound like a plan?

Wish me luck.