Sunday, March 6, 2016

How to Hit Volume and Gravity Targets with iMake's The Grainfather

I had pretty well mastered extract brewing in late 2014.  My recipes typically came out right at the target gravity and volume, with little or no variance.  My beers were good, and I had only ever tossed two batches, which were made without an actual recipe and turned out so sweet as to be undrinkable. I received iMake's The Grainfather RIMS brewing system in August 2015 as part of the Kickstarter.  In September, I started using it.

In retrospect, this was a lot to change at once.  I went from extract to all-grain.  I swapped out my kettle, immersion chiller, and other equipment for The Grainfather, all-grain brewing, and all-new recipes.  I did this without any help or guidance from others, apart from my own reading.  It's kind of surprising that I haven't had to toss a single Grainfather-made batch.

A recurring problem for me was that my final post-boil volume and gravity were rarely close to my recipes.  If my recipe was supposed to yield 5 gallons at 1.045 gravity, I'd end up with 5.5 gallons at 1.038 or 1.040.  Even when I boiled down to the target volume, my gravity was usually low.

Finally, I found that the problems were:
  • I'd been using the default sparge water calculation in the manual.  This meant that I was calculating sparge water based on a six-gallon batch instead of five gallons.  Adjusting the calculation for a five-gallon batch got me closer to the final volume target.
  • I didn't know enough about enzymes and their role in mashing.  In Palmer's book, I learned that the optimum balance of mash water to grain for a 60-minute mash is 1.5 quarts of water per pound of grain in the mash.  The Grainfather's figure results in a thinner mash that needs more time to convert starch to sugar.
The gravity problem was solved using three techniques as needed:
  • The adjusted sparge water calculation reduced pre-boil volume by one gallon.
  • In a few cases, my volumes were still a little high near the end of the boil.  In these cases, I removed the hops bags (to prevent over-bittering) and continued boiling until I hit the target.
  • Adding malt extract near the end of the boil to increase the gravity is also an option.
That last item (adding extract) carries a couple of caveats.  You should probably do this with at least 15 minutes left in the boil to ensure that the extract is boiled enough to sanitize it.  A second caveat is that if you're adding liquid malt extract, I've found that this tends to fall to the bottom of the Grainfather kettle and trigger its thermal cut-out switch.  This circuit-breaker-like device has to be reset by reaching underneath the Grainfather and pressing it in.  That can be risky with a full kettle of wort.  You're much better off using dry malt extract, which tends to float on the surface of the wort until it dissolves.

For my most-recent brew, a Blonde Ale, reducing the sparge water amount by a gallon allowed me to hit the post-boil volume on the mark.  Extending the mash time from 60 minutes to 90 minutes seemed to solve the gravity issue for that batch, which had a slightly higher pre-boil gravity and an on-target final gravity.  I have yet to have had to use malt extract since making those adjustments, but I keep some on-hand for just that contingency.

No comments:

Post a Comment