When I started brewing, I started with extract and recipes that someone gave me. Since I was dealing with known quantities and gravities (add 6.6lbs of extract to 6 gallons of water), there was not a lot of need for calibration, as long as I could measure accurately.
When I moved to all-grain brewing, things changed! Suddenly, it was much more complex, since the number of variables increased--something I understood at a high level, but didn't really appreciate. These are some of the things that affect your brewing:
- How good the crush of your malt is--finer isn't always better, you need intact husks to make a filter bed, etc.
- Grain temperature
- Weight of your mash tun (mine is a 10 gallon Rubbermaid cooler with a stainless steel false bottom)
- What your strike water temperature is, and whether it will get your single infusion mash to the desired mash step temperature.
- How big is your mash tun? Can you do a 5 gallon all-grain version of that Old Numbskull clone, or, because it would require 25lbs of grain, do you need to scale back the grain to 20lbs and plan to add some DME in the boil?
- How much dead space is there in your mash tun, and how much water will the grain absorb? How much extra strike/mashout/sparge water do you need to get 8 gallons in the brew kettle?
- What is your boil off rate? In other words, how much water will boil out of your wort each hour? This is critical, and it is affected by the strength of your boil, geometry of your kettle (as in how much surface area). A short fat kettle may boil off more than a tall skinny one because there is less surface are in the skinny kettle, even if they hold the same volume).
- How much wort will the hops absorb?
- How much dead space is there in your kettle? That is, when you open the valve in the bottom of your kettle, and let all the wort run out, how much will be left in the bottom? This shows a dip-tube to reduce the amount of dead space and get every last drop of wort that you can!
Why would carboys cause problems? Well, I switched from glass to the plastic kind because of two things:
- The weight of the glass carboys is a pain. I'm really not interested in lugging so much around and risking my back!
- Breakage! I read some stories about broken glass carboys that scared me, frankly! People have severed nerves, lost a lot of blood, etc., and for what?
BeerSmith is a fine piece of software, but I discovered that it was less "forgiving" than ProMash when it came to calibration. I had been making 6 gallon batches (that is 6 gallons going into the carboy, 5.5 gallons out after trub settled). I had also been kind of lazy about actually measuring the dead space in my mash tun and brew kettle. Only myself to blame there! I did calculate the boil-off rate, at least. But I plunged in with BeerSmith and used a sort of default equipment profile that was close to what I had--but not exactly. Finally, I used BeerSmith to scale the ProMash recipes from 6 gallons to 5, but wasn't using an accurate equipment profile so it (apparently) didn't work out so well.
Suddenly my batches were coming out weird. Pre-boil gravities were low. I ended up with 4 gallons in the fermenter instead of 5. Original gravities (post-boil) were off, or required supplementing with DME. In some cases after I tinkered, I ended up with a higher post-boil gravity, and had to dilute---which was OK because I collected less in my fermenter than the recipe predicted. In short, things weren't working the way they were supposed to!
This past weekend I measured the dead space in my mash tun and fermenter. I trust BeerSmith can figure out all the rest of the data from that, and I am looking forward to my next brew, to see how close I get to hitting my numbers. But the moral of the story is, measure, so you know how your equipment will behave! I will post a follow-up when I make my next batch.