I've been looking at ways to improve my brew efficiency, and one method that I've not seen much discussion of is increasing the boil duration.

Usually when I finish lautering, the wort coming out is still at 10 or 20 points, so there's more sugar to be extracted. Why not start the boil with the very first runnings that are collected, and boil a gallon or two off while lautering the rest? This would allow one or two more batches of sparge water to be circulated, to give the same final volume.

The only downside I can see is that this would take a bit longer, are there any reactions that I would need to look out for here?

3 Answers 3


I think the main downside would be the potential for excessive colour and flavour formation, although this would mainly affect pale beers, and it probably wouldn't be enough to push it out of style.

There's an article I linked to from a previous answer that talks about what happens during the boil, which also mentions pH as another variable. I don't know for sure, but I suspect you would reach a lower limit after a certain amount of time, so longer boiling may not have any noticable effect on pH.

As you mentioned, it would take a bit longer. I'd personally trade off the mash efficiency for my time, as the latter is more valuable to me.

  • I believe there's also the risk of astringency attached to over sparging.
    – DHough
    Sep 27, 2012 at 21:45
  • Just found this article: books.google.com/… which mentions that Cantillon evaporate off a minimum of 2k gallons from 9.5k gallons of wort. "Traditional lambic brewers boil their wort for four to six hours. Aside from condensing the wort, it also helps extract more bitterness from hops and counteract the high protein levels brought in by unmalted wheat. Over the course of a long boil, proteins coagulate and drop out of suspension." This doesn't contradict your point at all, but it's an interesting perspective.
    – Symmetric
    Sep 28, 2012 at 2:09

There are various ways to increase efficiency and one of them is to sparge more, collect more wort and boil longer. The issue with that is that the sparge wort is "lower quality" than the first runnings. According to Kai Troester, mash efficiency is composed of (conversion efficiency)x(lauter efficiency). Troester efficiency Obviously, raising either will increase the overall efficiency. However, you will produce better quality beer by raising the mash efficiency rather than the lauter efficiency. Look at grain crush, water amounts and pH as a way to increase conversion efficiency. If you batch sparge, tannin extraction should not be a concern with increased sparging unless you pH is way out of whack during the mash.

  • Good info. Can you elaborate on why the subsequent runnings are "lower quality"? Others have commented on tannin extraction and colour concentration, are there other things to consider as well?
    – Symmetric
    Sep 29, 2012 at 23:28
  • You can determine this by yourself simply by tasting the runnings. The earlier runnings have a rich, malty flavor. The later runnings taste "watered down".
    – Denny Conn
    Sep 30, 2012 at 16:15
  • Well, of course they taste "watered down"; the later runnings contain less sugar (and less of everything else that is extracted, both good and bad) and more water. That fact alone doesn't mean that you'll be left with inferior wort once you've boiled the later runnings down to a thicker consistency.
    – Symmetric
    Sep 30, 2012 at 22:10
  • Sorry, that hasn't been my experience.
    – Denny Conn
    Oct 1, 2012 at 15:31
  • I'll test this next brew-day; the fair experiment would be to boil the final runnings down to the same gravity as the original runnings, and then compare. I'm interested to know (in theory) what difference there could be between them.
    – Symmetric
    Oct 2, 2012 at 16:41

What you are suggesting sounds like you want to do a semi-normal high-gravity batch along with a two-penny beer (second run on the same grain bed) and adding the two together and boiling it down to get your desired volume. And, in the process of waiting for the second to finish, starting the boil on the first run to speed up the concentration process. Do I have that right?

Starting off, I concur with tallie about running longer than normal boils. I've ran my boils over the norms (~ +50%) and had slightly darker beer as a result. Aside from the slightly darker color, it didn't seem to change the flavor any when doing a full volume boil. (See next for the exception...)

However, with starting the boil with a smaller and more concentrated wort, you could potentially get some caramelization flavors as a result. I have had this happen to me when I first started brewing with extracts and didn't have a large boil kettle to work with. (I boiled a 5gal batch of extract in a 2gal kettle... can you say Sugar Daddy Candy?). Aside from the off character flavor, it was obviously darker than it should have been too.

Not to say these are unavoidable consequences... just that they are potential results. I don't honestly see the caramelization flavors coming through nearly as strong as in my overly concentrated example since I don't think your first run will be nearly that high in sugar.

All that as it may be... Considering your question is about a method of raising the efficiency of extracting sugar from your grain... Have you given any thought into trying Fly Sparging? I've not done it myself; but, it seems as thought you are already heading down a similar path anyway and this may get you into less trouble. Food for thought.

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