Partial Mash Boil Volume

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kgranger

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I moved houses and haven't fully set up my Spike system, but I'm itching to brew so I am going to try my hand at stovetop brewing in the meantime. I've never done partial mashing, pretty much went straight to all-grain when I started brewing. I really don't feel like buying anymore equipment since this is just temporary, and all I have on hand is a 5 gal brew kettle. Given the kettle's volume, I cannot do a full wort boil of ~6.5 gal, so I wanted to get some opinions about boiling with half the wort vol and topping off when cooled. I've done a couple extract batches back in the day like this, but the hopping rates were low, and darker in color (I am reading these are two concerns with more concentrated boil volumes). With more delicate styles, has anyone had good results with partial mashing and reduced boil volumes?
 

doug293cz

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Reducing the pre-boil volume by 50% will have a significant negative effect on your mash efficiency (lauter efficiency specifically.) When you have your recipe and full process decided, you can use my spreadsheet to characterize your new process vs. your previous process.

Brew on :mug:
 
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@kgranger : When you say "stove top partial mash", I'm visualizing something similar to "Easy Partial Mash Brewing" (link): mashing 2.5-gal-ish wort, boiling that wort, then adding DME/LME (to get to desired OG) and water to get to to 5 gal. With this process, there is a limit on the number of IBUs in a wort (around 100?), so doubling the amount of water will half the number of IBUs (around 50?). It's not a concentrated boil, so excessive darkening should not be a problem.
 

BWingate

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Why not do a 3 gallon batch? Depending on your stove, boiling will be quicker/easier/more robust too.
 
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kgranger

kgranger

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@kgranger : When you say "stove top partial mash", I'm visualizing something similar to "Easy Partial Mash Brewing" (link): mashing 2.5-gal-ish wort, boiling that wort, then adding DME/LME (to get to desired OG) and water to get to to 5 gal. With this process, there is a limit on the number of IBUs in a wort (around 100?), so doubling the amount of water will half the number of IBUs (around 50?). It's not a concentrated boil, so excessive darkening should not be a problem.
Yeah this is pretty much what I was imagining, thanks for the link! How should I adjust a partial-mash recipes hopping rates? Should I be doubling it to compensate for the dilution?
 
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kgranger

kgranger

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Why not do a 3 gallon batch? Depending on your stove, boiling will be quicker/easier/more robust too.
For at least the first time I do this, I am brewing for a little competition with my brew club, so my target is 5 gal just to make sure I have enough to serve. May step down to smaller batches in the future.
 
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How should I adjust a partial-mash recipes hopping rates? Should I be doubling it to compensate for the dilution?
You can try doubling the hops - but, as I mentioned earlier, there is an upper limit on the number of IBUs in a volume of wort.

How to Brew, 4e and Brewing Classic Styles (appendix C?) are good sources of information on "stove top" brewing (aka partial boil with late additions) and on partial mashes.
 
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