Need help to scale a recipe down.....

[PEACOCKSUIT]

I have bought all the ingredients to do the following recipe:

by steve_flack » Sun Oct 10, 2010 8:46 am

Brewed this earlier this year. Came out very nice.

Recipe: Kolsch
Style: 6C-Light Hybrid Beer-Kolsch

Recipe Overview

Wort Volume Before Boil: 45.00 l
Wort Volume After Boil: 42.00 l
Volume Transferred: 42.00 l
Water Added: 0.00 l
Volume At Pitching: 42.00 l
Final Batch Volume: 38.00 l
Expected Pre-Boil Gravity: 1.044 SG
Expected OG: 1.047 SG
Expected FG: 1.011 SG
Expected ABV: 4.7 %
Expected ABW: 3.7 %
Expected IBU (using Rager): 30.8
Expected Color: 5.6 EBC
Apparent Attenuation: 74.9 %
Mash Efficiency: 75.0 %
Boil Duration: 60.0 mins
Fermentation Temperature: 18 degC

Fermentables
Belgian Pilsen Malt 7.550 kg (90.0 %) In Mash/Steeped
UK Munich Malt 0.420 kg (5.0 %) In Mash/Steeped
UK Wheat Malt 0.420 kg (5.0 %) In Mash/Steeped

Hops
German Hallertauer Mittlefruh (4.2 % alpha) 100 g Bagged Pellet Hops used All Of Boil

Other Ingredients

Yeast: White Labs WLP029-German Ale/Kolsch

Mash Schedule
Mash Type: Full Mash
Schedule Name:Single Step Infusion (65C/149F)
Step: Rest at 65 degC for 60 mins

I am using BIAB. RajBoab has the same set up as me (60l boiler with 3kw element) and he says he starts with 32.5L of water and after mashing and boiling he ends up with roughly 23l.

In the recipe above the 'volume at pitching' is 42L. Could I just make 2 batches by simply halving all the ingredients? If so how much water would I start out with?

Cheers.

[boingy]

It's no problem to half the brew length by halving all of the fermentables and hops. If you wanted a different ratio that works too but it is often easier to use some brewing software to do the calcs for you.

As for how much water you need, it depends on your set-up.
In the mash the grain will absorb some and in the boiler the hops will absorb some plus you will have some dead space in the boiler and the amount lost in evaporation will depends on how vigorously you boil. The only real way is make an educated guess, note the results and then adjust the amounts next time you brew. Brewing software will also help you to calculate this stuff (but you still have to estimate the boil vigour and dead space.

[PEACOCKSUIT]

I could do with sitting down and figuring out properly how to use the beer software. Iv downloaded a free one but couldn't make head nor tail of it. There is spreadsheets on the biab info site but they look complicated as well. I will have to have a go at figuring them out.

[boingy]

The other way to do it is just to dive in. Half the recipe and start with 30 litres of water. The grain will absorb about 4litres (approx 1 litre per kg). If my understanding of BIAB is correct then there will be no other mash losses so you'll get about 26 litres in the boiler.Then just boil it for an hour. Typical boil losses are 10% to 15% per hour. You'll most likely and up within a litre or two of 21 litres (assuming a litre or so of dead space in the boiler.). The exact volume and OG is not massively important as long as they are fairly close you can just cool and pitch the yeast. If you end up with a high OG and/or a low quantity you can just top up with boiled water. If it is a high volume and/or a low OG you can boil a bit longer.

Whatever you do, taking notes of quantities and SGs at each point will help you tweak the process next time around.