RPh_Guy
Bringing Sour Back
Some online calculators express boil-off rates as a percentage! (specifically: morebeer, brew365, captainbrew)
No! Boil-off rate is more accurately expressed as gallons per hour (volume per time), not as a percentage (volume per volume per time). Using percentage makes the calculation inaccurate if the user modifies the length of the boil or the batch size from whatever process gave datum. Be careful using such a calculator.
For example, if while making a 1-gallon batch on the stove I observe 1 gallon boils off (50%) in one hour. If I scale the batch to 5-gallon the calc would say I need 10 gallons pre-boil! If I instead increase the boil to 2 hours, boiling off 50% per hour would require a 4-gallon pre-boil volume. Wrong again. I only need 3 gallons.
Moving along...
Every(?) online calculator includes wort shrinkage as a loss.
No! (Well, probably not.) Water does shrink by 4% from boiling point to 68F pitching temp. If you bring an unknown amount of water to a boil and then measure your mash and sparge water volumes, the default 4% value is great for you. It likely goes without saying, but is a bad idea.
If you start with excess water in a HLT and sparge until you reach a target pre-boil volume at 170F, that water will shrink by 2.5% on its way to 68F. However you probably aren't using a calculator for that process.
Doing a partial boil and then topping off is the only practical application of applying a 4% shrinkage loss when measuring water that I can see, but these calculators are designed for full-volume boils.
I measure my water out of the cold tap. During the winter when it's 45F the water actually expands by 0.17% start to finish -- reaching the fermentor at 68F.
Pure water densities for reference
45F 0.9999 g/mL
68F 0.9982 g/mL
170F 0.9738 g/mL
212F 0.9584 g/mL
Final thoughts...
Don't use hot tap water for brewing or cooking; your hot water tank concentrates minerals and microbes... and hot water may leach chemicals and/or lead from piping.
How do YOU measure out your brewing water?
Do you use an online calculator to determine correct mash and sparge water volumes to reach a target fermentor volume?
No! Boil-off rate is more accurately expressed as gallons per hour (volume per time), not as a percentage (volume per volume per time). Using percentage makes the calculation inaccurate if the user modifies the length of the boil or the batch size from whatever process gave datum. Be careful using such a calculator.
For example, if while making a 1-gallon batch on the stove I observe 1 gallon boils off (50%) in one hour. If I scale the batch to 5-gallon the calc would say I need 10 gallons pre-boil! If I instead increase the boil to 2 hours, boiling off 50% per hour would require a 4-gallon pre-boil volume. Wrong again. I only need 3 gallons.
Moving along...
Every(?) online calculator includes wort shrinkage as a loss.
No! (Well, probably not.) Water does shrink by 4% from boiling point to 68F pitching temp. If you bring an unknown amount of water to a boil and then measure your mash and sparge water volumes, the default 4% value is great for you. It likely goes without saying, but is a bad idea.
If you start with excess water in a HLT and sparge until you reach a target pre-boil volume at 170F, that water will shrink by 2.5% on its way to 68F. However you probably aren't using a calculator for that process.
Doing a partial boil and then topping off is the only practical application of applying a 4% shrinkage loss when measuring water that I can see, but these calculators are designed for full-volume boils.
I measure my water out of the cold tap. During the winter when it's 45F the water actually expands by 0.17% start to finish -- reaching the fermentor at 68F.
Pure water densities for reference
45F 0.9999 g/mL
68F 0.9982 g/mL
170F 0.9738 g/mL
212F 0.9584 g/mL
Final thoughts...
Don't use hot tap water for brewing or cooking; your hot water tank concentrates minerals and microbes... and hot water may leach chemicals and/or lead from piping.
How do YOU measure out your brewing water?
Do you use an online calculator to determine correct mash and sparge water volumes to reach a target fermentor volume?
