AG to Partial Mash/Partial Boil?

[sumbrewindude]

I hate double posting, but I tried in the Beginners Forum and got a lot of looks and no nibbles, so I thought I'd repost this question back into the appropriate sub-forum and try here.

So - I started this journey out with AG right off the bat. Love it, very happy with it.

That said, I've never done a partial mash/extract batch. I didn't really see the point when I'm doing sub 3gal recipes. If I did do a 5gal batch for some reason, it'd be a limitied thing - so because of that I'm kicking around the thought of exploring partial mash for them. My equipment is fine for smaller boils, but I don't have the capacity to boil 6-7gal of wort for a full boil 5gal AG.

From the general look of things, I can sub out the base malt (or part of the base malt) for LME/DME and mash the specialty grains like usual. Once the mash is done, just boil as usual and add the DME/LME and away we go.

Where I'm getting confused is with hop additions and water volume.

From what it looks like, the water amount is less that a full AG boil and then top up water is added after cool down to top up the carboy. How is this water volume calculated for boil?

Second question relates to that boil water - do I need to compensate with more hops during the boil due to the lack of water? I thought I remembered something about due to a higher gravity that hop additions would need to change.

In looking at a few posts here in the Extract forum and would appear that boiling a full amount is always perferred over a partial boil, but would it be terrible if I shorted the water by 30%, then added it on the backside?

Trying to see how I can migrate some of my recipes to partial mash, and what kind of volumes I'll be dealing with for boiling.

Thanks gang.

 

[aiptasia]

From what it looks like, the water amount is less that a full AG boil and then top up water is added after cool down to top up the carboy. How is this water volume calculated for boil?

Your water losses will be a lot less than all grain. Since you have little to no grains to absorb fluids and the vigorous boil is a lot less with a tabletop batch vs. an outside gas burner batch, you'll just have to gauge what you water loss usually is. I think for grain absorption you're looking between 0.15 to 0.20 gallons per pound of grains. Typically, I see about a half gallon of boil off for tabletop batches at 60 minutes. So, when I do partial mashes, I do 3.75 gallons of water and wind up with just a little over 3 gallons of wort when all is said and done.

Second question relates to that boil water - do I need to compensate with more hops during the boil due to the lack of water? I thought I remembered something about due to a higher gravity that hop additions would need to change.

No. I usually don't have to add extra hops as long as my pre-boil pH is in line. I do add some gypsum to buffer up distilled water on IPA's though.

In looking at a few posts here in the Extract forum and would appear that boiling a full amount is always perferred over a partial boil, but would it be terrible if I shorted the water by 30%, then added it on the backside?

Maybe but it's what I usually do on the tabletop and the beer comes out great. I usually aim to have three gallons of wort in the boil pot by the end of the boil and pour two gallons of cold distilled water into the primary. When the boil is done and the wort is cooled to about 85 degrees, I pour the wort into the cold water in the primary and mix the hell out of it to cool it off and thoroughly oxygenate it. The extra cold water helps lower the temperature faster to pitching temperatures.

Again, you should be able to manage full boil sizes (even with a hot break) to about three gallons full volume and up to about five or six gallon batches if you do the method I just described. I wouldn't do a full boil batch in a five gallon pot with a boil volume over four gallons. Even then, i'd use fermcap S to completely dissolve the hot break. It's a complete bitch and a half cleaning up hot wort from a stovetop.

 

[Weezy]

I do 3 gal batches. I do something similar to what you're thinking but instead of going for higher volume, 3 gal to 5 gal, I do this to get to high grav 3 gal batches.

If you're doing true partial mash, then adding a couple gallons and some DME/LME to get to a 5 gal batch, id recommend calculating out two recipes. say, start with the full 5 gal recipe, with all parts included... grain, extract, and all hops. then take out the extra water and the extract, leaving the hops unchanged. Do this so that you can do a standard all grain batch at the lower volume, so you know what numbers you need to hit. At flame out and you're satisfied with the SG of the all grain portion, just dissolve the extract in the wort. Cool and top off in the carboy.

 

[sumbrewindude]

I do 3 gal batches. I do something similar to what you're thinking but instead of going for higher volume, 3 gal to 5 gal, I do this to get to high grav 3 gal batches.

If you're doing true partial mash, then adding a couple gallons and some DME/LME to get to a 5 gal batch, id recommend calculating out two recipes. say, start with the full 5 gal recipe, with all parts included... grain, extract, and all hops. then take out the extra water and the extract, leaving the hops unchanged. Do this so that you can do a standard all grain batch at the lower volume, so you know what numbers you need to hit. At flame out and you're satisfied with the SG of the all grain portion, just dissolve the extract in the wort. Cool and top off in the carboy.

I think this is exactly what I was hoping to hear.

I'm going to repeat it back in my own goofy words so hopefully you can correct me if I'm wrong in understanding you -

1) Develope 5gal recipe, using both regular AG components and LME/DME.
2) Separate out LME/DME component, drop water to managable level (3-4gal) while leaving hop additions at 5gal amount.
3) Take readings for 5gal and pseudo 3gal recipes for reference values.

On brew day:
1) Mash AG component (specialty grains/limited base) as normal.
2) Perform reduced 5gal brew, with full strength hop additions
3) At FO add LME/DME to raise SG; check/verify.
4) At carboy, add top off water to OG value calculated from original 5gal recipe; check/verify.
5) Pitch and be happy.

Did I understand correctly?

The only thing I'm confused about, and this is simply because that goofy computer program I'm using (BrewTarget), is the hop additions. Is the IBU extraction a function of the time in the boiling water, or does the amount grain have an effect on it? The reason I ask is because when I play with the numbers a little I get different IBU's for the boil..

Not a huge difference, but enough that it effects the "style" tolerances.

Thanks again everyone for the input, I appreciate it.

 

[OptimusJay]

Once in awhile I do a partial mash/partial boil brew, usually when it's too cold outside for using propane burner and 10gal pot. In those cases I brew indoors using an electric oven. Getting 6 gallons to boil (to net a 5 gal recipe) is near impossible. Therefore I use a 5 gal pot and aim to have around 3.75 of wort at the start of the boil. If you use Beersmith the link I'll post below will probably answer all your questions. This is what I do when converting a full AG batch into a partial mash/partial boil recipe. It works great.

https://www.homebrewtalk.com/f12/converting-recipes-partial-mash-partial-boil-beer-smith-142244/

Jay

 

[Weezy]

Your process looks good.

The ibu equations, both tinseth and tager where tinseth is more sensitive to it, do account for wort density. But, its been shown that this is incorrect but no one ha developed new equations yet.

 

[sumbrewindude]

Thanks again Jay and Weezy!

That link explained it perfectly. I can adapt that to BrewTarget without issue.

Weezy, I'm using tinseth, so that would explain the IBU shift I'm seeing. After seeing the same thing in BS2, I'll just account for it and move on - not worth stressing over it seems.

Thanks again guys, I searched all over for a post like that and couldn't find it - it was a huge help!