How to decrease 5g to 2.5g

[Will_the-new-brewer]

I have read some horror stories about people going from 5g to 10g AG recipes...by doubling everything...water included. It seems to end in disaster.

What will I face by going from 5g to 2.5g AG?

 

[whovous]

I cut everything but yeast in half. I use a whole package of yeast. Later, when I went from 2.5 to 3.0 gallons, I just added 20% to everything, yeast excluded.

 

[PhillyBrewDoug]

When I’ve converted recipes down I’ve noticed that the speciality malts scaled down more. Going smaller seems to give them more impact. Learned this the hard way on a porter.

For boil hops, it’s more about keeping the same AAU/IBU targets. You’ll have to do math anyways as the AA% of the hops you use are bound to be different than the original brewer. For dryhopping, I would use 50% of what the 5G recipe calls for.

For water, start with cutting it in half, but you’ll have to adjust for your system. I end up using just shy of 4 gallons for my BIAB brews to account for my losses at kettle and fermenter.

Honestly, using BeerSmith to do the initial scale down of recipes has made it much easier to do 2.5G batches. If you can get your hands on that or something similar that you trust, use it.

 

[Griffin495]

Most of my batches are 2.5 gallon (some are one gallon or even 1.5gallon). I take a recipe that I want to try, input it into Brewer's Friend and use the scale tool to scale it to 2.5 gallons and have no issues. I usually take the hops and convert it from ounces to grams to be a little more precise, though.

 

[IslandLizard]

I have read some horror stories about people going from 5g to 10g AG recipes...by doubling everything...water included. It seems to end in disaster.

What will I face by going from 5g to 2.5g AG?

If a brewer doesn't understand the mechanisms involved in brewing, yeah they'll end up with some different numbers (IBU, OG, etc.), when scaling a recipe.

Since you halve the recipe, use half the ingredients, throughout. It's that simple!
This includes yeast. Now opened dry yeast cannot be stored that long, so you may as well pitch the whole pouch unless you brew 2 half batches within a week.

Now the amount of water used will not be quite half, depending on your equipment. Say the 5 gallon recipe expects 1 gallon boil-off per hour. If you halve the recipe, chances are you still boil off a gallon per hour. It may be a little less (less powerful heat source, smaller kettle, etc.), but it's unlikely you'd boil off only half a gallon per hour.

Any deadspace or heat loss in your mash tun carries forward at it's full volume and amount, regardless of amount mashed. Same for certain other equipment losses, such as wort left inside a pump, chiller, kettle, etc. So review and compare your equipment compared to the equipment typically used for 5 gallon boils.

I'd say after one brew you can have that all figured out and know what additional tweaks to make.

 

[IslandLizard]

I usually take the hops and convert it from ounces to grams to be a little more precise, though.

So true!

Any additions under 1 oz should be weighed in grams, regardless, not just hops.

 

[small_b_brewing]

Wow, learning a lot in this thread, I've just been cutting everything in half and double checking my IBUs in a calculator before hand.

 

[deadwolfbones]

Just use an online recipe calculator like Brewer's Friend or Brewtoad. They have scaling functions.

 

[IslandLizard]

I’ve noticed that the speciality malts scaled down more

I too noticed that scaling in BS isn't linear.
Any ideas why that should be? For example, 5% Honey Malt should remain 5%, isn't it?

The only reason I can see is if extract efficiency of base malts in smaller batches were less, hence all cara, specialty, roast, etc. scale down with it. But that's not necessarily the case. Chances are, efficiency is actually higher.

 

[PhillyBrewDoug]

I too noticed that scaling in BS isn't linear.
Any ideas why that should be? For example, 5% Honey Malt should remain 5%, isn't it?

The only reason I can see is if extract efficiency of base malts in smaller batches were less, hence all cara, specialty, roast, etc. scale down with it. But that's not necessarily the case. Chances are, efficiency is actually higher.

I agree that logically it would make sense for the percentages to stay the same. It might actually be because efficiency is probably higher and BS is targeting the OG during the scale down, and making the adjustments match that. That’s just a guess, though.

I think some experimenting is needed this weekend to see if an “everything divided by 2” and a BS scaled down recipe produce comparable beers. Good thing it’s scaling down!

 

[Will_the-new-brewer]

I did a check on Brewers Friend to scale down to 2.5g. It split everything in half except for water...that was a little different. The Gravity Checks and ABV stayed the same, IBU fluctuated by 5 (if memory serves).