KernelCrush said:
Is there a resource on how to do a proper calibration batch?
Calibration batches are a pro thing. Nothing glamorous, they're just a reference measurement and a guide for optimizing brewery flow. Being consistent is everything, so weight is the best way to accomplish this.
I try to target easy numbers. I know your engineering background, but I'm going to add extra detail to the procedure for those that may have questions.
You'll need some tools:
#14 sieve (14 strands per inch)
#4 sieve, or just mesh fabric. (optional)
Both of the above are available on ebay
Scale precise to .01 oz. Even better if it'll do grams.
So, Let's shoot for 75% efficiency.
Precisely measure 20 lbs (10kg) of pale malt.
First calibration: Malt crush
Take a 8 oz sample of the malt.
Mill it
Weigh it and make sure it is still 8 oz. Look for places in the mill that might be collecting grain and clear them.
Don't shake it or compact the sample. Ideally, it should be as fluffy as it comes out from the mill. Sieve the crushed malt through. Capturing the dust is a plus, but not required.
Use a fresh paint brush to remove any particles that went through the sieve but clung below the screen.
Carefully pour the remaining malt into a clean container to weigh. Make sure to tare the scale to the container.
You should have between 5.2 and 5.6 oz of grist. This represents 65% to 70% of the grain weight. Above that and the mill gap is too wide, below that and it might be too fine. The number in a pro brewery is 50%. This is pretty perfect for a homebrewing setup and shoots for 85% total mash efficiency when fly sparging.
Secondary, you can sieve this through a #4 screen to separate out large and uncrushed grains. This weight should not exceed 5% and is hopefully just 2%. Look for out of parallel rollers as a source of large sized particles. This may not be correctable since at least one manufacturer (Schmidling) purposely engineers their mill to have a varied gap.
Obviously, you'd repeat the above until the crush lined up with optimal settings.
Mill the grain and make sure the total weight is still 20 lbs. Some makeup grain may be required if you had to repeat the gap procedure a lot.
Weigh out 40 lbs of water and heat to strike temperature, targeting 150 degrees. If your procedure is to preheat, do this with separate water. Drain completely. A few drops left are insignificant, a measurable puddle would be undesirable.
Mash in with 100% of the strike water, targeting 150 degrees. Mix thoroughly, but not too long. The crush should be sufficient to allow mixing. Nothing good comes from fondling the mash. Let this sit for 45 minutes.
While the mash rests, prepare 20 lbs more water and heat to 180 F
At 20 minutes into the mash, take a pH reading. This is your nominal pale grist pH. All future acid adjustments spring from this number.
At 30 minutes, take a gravity reading. Based on the tables that Tom posted, if you're at saturation at this time, you have optimal mash conditions. If you're not, take another gravity every 5 minutes and record the rise. At the point it doesn't rise for 3 consecutive readings, you're at saturation. Compare that to the mash conversion tables.
One note on the iodine test and why I don't include it. This measures large hydrolyzed starches that haven't debranched. A wort can pass the test in 25 or 30 minutes, but this DOES NOT guarantee full conversion. Measuring wort gravity tells you much more about that.
Once your wort is at full saturation, add the 10 lbs of water, stir gently. This should raise the mash to 155 F and excite any remaining alpha amylase into working faster.
Let this rest for 5 minutes and take a gravity reading. If the number falls below the same relative saturation, you may have a grist that is too coarse. Simply, the additional water isn't pulling enough sugar from the grain. This is confirmed if the gravity rises because the amylase is converting starch into dextrin.
This may have created questions, I will stop and pick up the sparge boil in a day or so.
