Your best way forward is to learn how to scale any recipe to suit your system. I'd suggest using a trial of Beersmith or Brewfather.app.
When scaling a recipe, the following should stay the same:
OG, FG, IBU and colour (EBC/SRM).
The following scale linearly, i.e. a 5 L batch uses/yields 5/19ths as much as an American 5-gallon recipe or 5/23rds of an Australian large batch:
Amount of yeast to pitch, hops (more or less), end kettle/fermenter volume.
Your grain scales linearly if your efficiency is the same as the original recipe's. Your grain absorption follows this.
The following is constant (per hour):
Your system's boil-off rate.
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So putting it all together with an example:
1. Determine your system's boil-off rate. I'd suggest just filling your pot up to the 7 L mark, bring to a rolling ball and boil it with the lid off for 1 hour.
Example = 2 L/hour.
2. Nominate a starting mash efficiency. I recommend assuming 65%, then tweaking it as you go from batch to batch. I'm at the stage where a fine-crush BIAB with no sparge gets me 85-90% every time. You can get there, but focus on consistency above all else.
3. Nominate a grain absorption rate. 0.6 L/kg for grain absorption is about right for BIAB with bag squeezing.
You can now scale a recipe. Let's use a
SNPA clone. Firstly, it uses the following grains:
11.5 lb = 5.23 kg pale malt
14.54 oz = 0.41 kg crystal 60 malt
Now this is for a 6.5 American gallon batch with 79% efficiency (I know it's technically brew house, and not mash, but let's just use it to start with).
Your scale factor is desired_litres/their_litres * their_efficiency/your_efficiency
= 5 / (6.5 * 3.79) * 79/65
=
0.25
So you need 0.25*5.23 = 1.31 kg pale malt and 0.25*0.41 = 0.1 kg crystal malt
Next work out your water:
Total water = end kettle volume + grain absorption loss + boil-off volume
= end kettle volume + grain absorption loss + (boil-off rate * time in hours)
This is a 70-minute boil, which I wouldn't bother with, but it illustrates how to scale your volume for boil time...
Total water = 5 + 0.6 * (1.31 + 0.1) + 2 * 70/60
= 8.18 L
~= 8.2 L
Hops are easy – just use your above scaling equation, but don't modify it for mash efficiency:
Hop scale factor = 5 / (6.5 * 3.79) = 0.2
So 0.5 oz becomes ~3 g
1 oz becomes ~6 g
2 oz becomes ~11 g
Now you know what to do for water, grain, hops and yeast! I'd suggest working through it manually, and checking against these numbers. If you end up with grain less than 1 kg (other than a saison) or more than 2 kg (other than a wee heavy or imperial stout), you've probably made an error.
The next step is to tweak your parameters to make your numbers more accurate for the next brew.
If you collect a pre-boil volume and pre-boil gravity (easiest with refractometer)
and a post-boil volume and OG, you can adjust everything. If you only have a hydrometer and want brew day simpler, I think just work with the info you have.
- If OG is too high, look at your volume. If your volume is correct, then your efficiency was underestimated. Scale it by taking the gravity values after the 1. part of your reading. E.g. if you expected an OG of 1.055 but got 1.062, your efficiency was actually (62/55) * 65 = 73%. Vice versa for OG/efficiency too low.
- If your volume is too high, either you overestimated boil-off or grain absorption. If you did a boil-off test before starting, I'd assume grain absorption needs adjusting for your next batch. If your volume is too high, your OG should also be proportionately lower, e.g. 5 L @ 1.055 = 5.5 L @ 1.050 for a given efficiency. To work out your actual efficiency, calculate (actual_vol / target_vol * (1 - actual_OG) / (1 - target_OG)) * assumed_efficiency. For example, if you got 5.2 L @ 1.050 for this recipe, your efficiency would be:
- 5.2/5 * 50/55 * 65 = 61.45 (%)
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Hope that makes sense. I think it's worth learning how to work it out mathematically yourself, as brewing software has quirks. I did it the manual way for the first few times I used Brewsmith before I trusted that I had all my profiles correct.
Let me know if you have any questions or have found mistakes in my working.
